Biochemical basis of insect-plant interaction under climate stress: Mechanisms, adaptations and implications for agriculture

Introduction

Insect-plant interactions are essential ecological relationships that can be antagonistic, commensal, or mutualistic. Antagonism occurs when insects harm plants by feeding on them, reducing growth and health. In contrast, commensalism involves insects benefiting from plants with little or no effect on them, such as aphids extracting sap in small numbers. Mutualistic interactions benefit both partners, as seen in pollination, where insects like bees gain nectar while enabling plant reproduction (Schoonhoven et al., 2005; Belete, 2018) [5] . These diverse interactions not only shape ecosystems but also influence agricultural productivity and reflect the co-evolutionary dynamics between plants and insects, often mediated by complex biochemical signals and adaptive traits. Plants protect themselves from insect attacks using two main strategies: direct defences and indirect defences. Direct defences include physical barriers such as trichomes, spines, thorns and lignified tissues, and chemical compounds that slow down insect feeding, growth, development, and reproduction. Indirect defences do not harm insects directly, but work by emission of specific volatile compounds that attract predators and parasitoids, functioning as "extended bodyguards" (Howe and Jander, 2008; Dicke and Baldwin, 2010) [33,20] simultaneously enhancing salicylic acid (SA)-mediated pathways that strengthen resistance against pathogens (Belete, 2018; Zavala et al., 2017) [5,104] This hormonal rebalancing may leave plants more vulnerable to insect herbivores but more tolerant to microbial infections. Such trade-offs highlight the importance of understanding how climate-driven shifts in plant biochemistry will influence future plant-insect interactions and the resilience of agricultural systems.

Climate Stress and Plant Biochemistry 2.1 Primary Metabolism Under Climate Stress

Primary metabolism forms the biochemical foundation of plant growth and defence, encompassing carbon assimilation, nitrogen metabolism, carbohydrate production, and amino acid biosynthesis. These processes are highly sensitive to stressors such as elevated CO₂, heat, drought, and ozone, which influence plant-insect interactions.

Carbon and Nitrogen Metabolism

Elevated CO₂ enhances photosynthetic carbon fixation in C₃ plants, increasing biomass and carbohydrate supply, but long-term exposure often leads to photosynthetic acclimation due to carbohydrate feedback inhibition (Ainsworth & Long, 2005; Leakey et al., 2009) [2,50]. Heat and drought stress damage photosystems and limit stomatal conductance, while ozone accelerates oxidative injury, degrades chlorophyll and decreases Rubisco activity (Fiscus et al., 2005) [25] . Elevated CO₂ also drives nitrogen dilution, lowering tissue protein content and altering C: N ratios (Taub & Wang, 2008) [83] . Heat may temporarily stimulate nitrate reductase activity, but prolonged drought or ozone typically suppresses nitrogen assimilation by impairing root function and reducing enzyme activity (Pell et al., 1997; Bloom, 2015) [65,15] . These shifts reduce plant nutritional quality for herbivores, often reducing their growth and reproduction.

Carbohydrates and Amino Acids

Carbohydrates serve as energy reserves and also as signalling molecules in stress adaptation. Elevated CO₂ enhances soluble sugars and starch reserves, whereas drought restricts transport and metabolism, and high temperatures deplete reserves through increased respiration (Couée et al., 2006; Leakey et al., 2009) [17,50] . Ozone inhibits sugar metabolism via oxidative degradation. Amino acids respond variably: CO₂-induced nitrogen limitation lowers total amino acid content due to nitrogen limitation (Taub & Wang, 2008) [83] , while drought and salinity promote accumulation of Osmo protectants such as proline, glycine betaine, and GABA (Krasensky & Jonak, 2012) [43] . Heat stress induces synthesis of amino acids required for heat-shock proteins, and ozone alters amino acid balance as part of stress signalling. Since amino acids and sugars are central determinants of herbivore food quality, climateinduced alterations in their availability directly affect insect feeding, growth, and survival.

Secondary Metabolites Under Climate Stress

Secondary metabolites are a chemically varied category of substances crucial for signalling, defence, and environmental adaptability. Among them, terpenes, phenolics, flavonoids, tannins and alkaloids are pivotal in mediating plant-insect interactions. Temperature, increased CO₂, ozone, and drought significantly affect their biosynthesis, accumulation, and emission, changing plants' ecological interactions and defence ability.

Phenolics, Flavonoids and Tannins

Phenolic compounds derived from the phenylpropanoid and shikimate pathways serve as antioxidants, structural components, and defence molecules. Flavonoids are a large and multifunctional class of phenolics that are highly responsive to abiotic stress. Elevated CO₂ often enhances phenolic and tannin production via carbon-nutrient balance (Peñuelas & Estiarte, 1998; Barbehenn & Constabel, 2011) [4, 66] . Drought, UV-B, and ozone further promote their accumulation as scavengers of reactive oxygen species (ROS) (Agati et al., 2012) [1] . Tannins interfere with protein digestion, while flavonoids act as UV protectants and signalling molecules. However, due to resource trade-offs, phenolic and tannin levels may plateau or decline under severe or prolonged stress. These compounds generally strengthen defence but vary across species and stress combinations.

Terpenes

The most prominent family of secondary metabolites, terpenoids, have two functions: direct defence (toxicity, deterrence) and indirect defence (herbivore-induced volatiles attracting natural enemies). Their biosynthesis and release are highly sensitive to abiotic stress. Elevated temperature and moderate drought stimulate terpene release, whereas severe drought suppresses synthesis (2012 & Llusià, 2003; Loreto & Schnitzler, 2010) [55] . Elevated CO₂ produces species-specific outcomes, with some plants accumulating more stored monoterpenes. Ozone often induces terpene release as part of oxidative stress signalling. These shifts strongly influence insect behaviour and multitrophic interactions.

Alkaloids

Alkaloids are nitrogen-rich substances acting as neurotoxins and deterrents. Their production depends on nitrogen availability. According to the nitrogen restriction theory, elevated CO₂ often results in nitrogen dilution in plant tissues, which lowers alkaloid concentrations (Zavala et al., 2013) [102] . Conversely, by upregulating stress-related pathways, drought and other stressors can promote the production of alkaloids (Hartmann, 2007) [30] . These context-dependent responses suggest that climate stress may reduce or enhance plant chemical defences depending on the balance between carbon and nitrogen metabolism.

Signalling Molecules Under Climate Stress

Plant signalling molecules such as jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) play central roles in coordinating defence responses against herbivores and pathogens. Their biosynthesis and signalling networks are susceptible to climate stress, which can shift defence allocation and alter insect-plant interactions.

Jasmonic Acid (JA)

JA is an essential protective regulator against chewing insects by promoting the synthesis of volatile chemical compounds, alkaloids, terpenoids, and proteinase inhibitors. Elevated CO₂ frequently suppresses JA signalling due to nitrogen dilution and restricted substrate supply (Zavala et al., 2008) [103] , which weakens inducible defences. In contrast, drought and heat generally enhance JA accumulation, linking it with stomatal regulation and osmotic adjustment (Sharma et al., 2013) [77] . Ozone also stimulates JA pathways, since oxidative stress mimics herbivory and activates similar defence cascades (Vuorinen et al., 2004) [88] .

Salicylic Acid (SA)

Salicylic acid (SA) is the primary mediator of resistance against piercing-sucking insects and biotrophic pathogens. It frequently has a negative connection with JA, and stress can upset this equilibrium. Increased CO₂ has had a variety of effects. SA signalling may increase in some situations, enhancing pathogen resistance but potentially suppressing JA-based herbivore defence (Zhou et al., 2019) [108] . Drought typically induces SA, aiding ROS detoxification and stomatal closure, whereas heat stress can suppress SA and lower disease resistance (Khan et al., 2015) [42] . Ozone consistently increases SA accumulation, as part of systemic acquired resistance (Yalpani et al., 1994) [97] .

Ethylene (ET)

Ethylene is a multipurpose hormone that influences defences mediated by JA and SA. Elevated CO₂ usually reduces ET synthesis, weakening synergistic defence signalling (Zavala et al., 2008) [103] . Heat stress strongly enhances ET, accelerating stress tolerance pathways, senescence, and abscission (Suzuki et al., 2014) [82] . Depending on its intensity, drought stress can change defensive activation and growth regulation by raising or lowering ET. According to Booker et al. (2009) [10] , exposure to ozone causes a sharp rise in ET emissions, which speeds up stress signalling and leaf withering.

Volatile Organic Compounds (VOCs) and Tritrophic Interactions

Plants emit diverse volatile organic compounds (VOCs) that mediate both plant-plant signalling and plant-insect-enemy interactions. Two key groups are green leaf volatiles (GLVs), released immediately after tissue damage, and herbivore-induced plant volatiles (HIPVs), which are produced more slowly in response to insect feeding. These compounds play a central role in indirect defence by attracting predators and parasitoids of herbivores, thereby shaping tri-trophic interactions.

Green Leaf Volatiles (GLVs)

GLVs are C₆ compounds such as (Z)-3-hexenal, (Z)-3hexen-1-ol, and (Z)-3-hexenyl acetate, released instantly after mechanical or herbivore damage. They function as "alarm signals", priming defences in neighbouring plants (Engelberth et al., 2004) [21] and providing chemical cues for natural enemies of herbivores (Arimura et al., 2009) [3] . GLV release is influenced by climate stress: heat and drought frequently cause an increase in GLV emissions because of increased lipid peroxidation, whereas high CO₂ can decrease them (Loreto & Schnitzler, 2010) [55] .

Herbivore-Induced Plant Volatiles (HIPVs)

HIPVs include terpenoids, phenylpropanoids, and GLVs, produced after herbivore feeding. They attract parasitoids and predators (Turlings & Erb, 2018) [84] , while also mediating plant-plant communication. HIPV responses to climate stress are complex: Elevated CO₂ often reduces HIPVs, weakening parasitoid attraction (Gouinguené & Turlings, 2002) [28] . High temperature generally increases HIPV release but may alter timing and blend composition (Peñuelas & Staudt, 2010) [68] . Drought can suppress HIPVs due to reduced metabolic activity yet enhance specific compounds as stress signals (Copolovici et al., 2014) [16] . Ozone stimulates VOC synthesis but rapidly oxidises HIPVs in the atmosphere, reducing their signalling range (Holopainen & Gershenzon, 2010) [32] . Climate-driven changes in GLVs and HIPVs can disrupt these tritrophic interactions, reducing herbivore suppression or shifting community dynamics (Zavala et al., 2017) [104] . For example, reduced HIPV signalling under elevated CO₂ may limit parasitoid efficiency, while moderate warming may transiently enhance enemy attraction.

Insect Biochemical Adaptations

Insects and plants are engaged in a continuous evolutionary arms race, where plants defend themselves with toxic secondary metabolites and insects respond with specialised behavioural, physiological and biochemical mechanisms, which allow them to feed on chemically defended plants (Berenbaum, 2001; Karban and Agrawal, 2002) [7,40] .

Digestive enzymes

Insects play a crucial role in shaping their digestive enzyme activity within the midgut according to the plants they consume, enabling them to efficiently process and extract nutrients from diverse and often chemically defended plant tissues (Kutty and Mishra, 2023; Beran and Petschenka, 2022) [6,48] . Digestive enzymes are thus central to insect adaptation, allowing insects to thrive in varied and sometimes hostile plant environments. Environmental factors such as temperature and elevated CO₂ can alter enzyme activity and gut efficiency, but insects compensate by adjusting enzyme secretion to maintain effective nutrient absorption under stress (Zhang et al., 2024) [106] . In addition, some plant-feeding insects acquire novel digestive enzyme genes from gut microbes through horizontal gene transfer, providing them with new metabolic tools to digest complex plant materials more effectively (Wang et al., 2021) [91] .

Detoxification enzymes

Detoxification enzymes in insects (like P450s, GSTs, UGTs) act as biochemical shields that work against toxic plant metabolites, ensuring survival in chemically hostile environments. Insects employ a three-phase detoxification system to counter harmful plant secondary metabolites. In the first phase, ingested compounds are broken down by enzymes such as cytochrome P450s, carboxylesterases, and flavin-containing monooxygenases, either within the insect itself or through symbiotic gut microbes. In the second phase, toxic intermediates undergo conjugation reactions, mediated by enzymes like glutathione S-transferases and glycosyltransferases, which enhance solubility and facilitate excretion. Finally, in the third phase, the modified metabolites are expelled from cells via ATP-binding cassette transporters (Hu et al., 2019; Heidel-Fischer and Vogel, 2015; Chen et al., 2020) [35,31,15] . Within this framework, Spodoptera litura detoxifies the plant defence compound xanthotoxin through UDP-glycosyltransferases (UGTs), whose expression and activity are essential for larval tolerance. Notably, the CncC/MafK transcriptional pathway has been shown to directly regulate UGT expression, thereby mediating xanthotoxin detoxification and illustrating how insects integrate core detoxification phases with transcriptional control mechanisms to adapt to plant chemical defences (yang et al., 2025) [98] .

Sequestration strategies

The ability of insect herbivores to selectively absorb and store toxic compounds from their host plants is a key trait influencing their survival and success on highly defended plants, especially in environments with numerous natural enemies (Opitz and Muller, 2009) [62] . Insects achieve this through a combination of physiological mechanisms: passive diffusion or active transport proteins such as ABC and SLC transporters, depending on the chemical properties of the compound, move plant-derived toxins-like glucosinolates-into protected storage sites, including the haemolymph, cuticle, or fat body (Dermauw and Van, 2014) [18] . For example, in the milkweed bug (Oncopeltus fasciatus), the cardiac glycoside digitoxin is thought to cross the midgut lining passively. In contrast, in the desert locust (Schistocerca gregaria) and the American cockroach (Periplaneta americana), the midgut prevents this compound from entering (Scudder and Meredith, 1982) [76] . This demonstrates that the ability of plant defence chemicals to cross the gut barrier is a significant factor shaping the evolution of sequestration strategies. In the poplar leaf beetle (Chrysomela populi), scientists discovered an ABC transporter, CpMRP, strongly expressed in the defensive glands. This protein uses energy from ATP to move salicin, a plant compound ingested by the beetle, into storage vesicles within the glands. Salicin is transformed into salicyl aldehyde, the beetle's primary defensive secretion. When CpMRP is knocked down, the beetles cannot produce their chemical defence, showing that CpMRP plays a crucial role in capturing plant compounds and enabling the beetle's protective chemistry (Strauss, 2013) [80] . Once stored, these compounds are often further processed by detoxification pathways. Enzymes modify the toxins through conjugation (Phase II) and then transport them (Phase III), enabling insects to retain the defensive benefits of the chemicals while avoiding self-harm (Jeckel et al., 2022) [39] . Early research in the 1960s and 1970s provided striking evidence of this phenomenon: monarch butterflies feed on toxic milkweed, store the toxins, and become poisonous to predators such as birds (Brower et al., 1967; Malcolm, 1994) [11,57] . Initially thought to be a unique example, subsequent studies have shown that many insect species specialising in toxic plants similarly sequester plant chemicals to enhance their survival (Nishida, 2002; Opitz and Muller, 2009) [61,62] . These findings illustrate how absorption, storage, and detoxification allow herbivorous insects to exploit plant defences as a powerful protective strategy.

Antioxidant defences

Antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidases (GPX) help neutralise reactive oxygen species (ROS) produced in insects during metabolic or environmental stress, thereby protecting cellular components from oxidative damage (Felton and Summers, 1995) [24] ; in particular, these enzymes provide defence against oxidative stress induced by plant defence compounds.

Tri-Trophic Interactions under Climate Stress

In natural ecosystems, plant-insect interactions rarely occur as simple two-way relationships; instead, they often appear in complex tri-trophic systems where plants, herbivores, pollinators, and natural enemies such as parasitoids and predators are linked through intricate biochemical and ecological signals (Turlings and Erb, 2018; Strauss and Irwin, 2004) [84,81] . These interactions are governed mainly by herbivore-induced plant volatiles (HIPVs), floral traits, and nectar resources, which influence herbivore behaviour and guide natural enemies and pollinators. However, climate stressors-including heat waves, drought, and air pollution alter the quantity, composition, and persistence of these chemical signals, thereby disrupting natural pest control and pollination services.

Plant-Herbivore-Parasitoid Interactions

Plants under herbivore attack emit a diverse blend of herbivore-induced plant volatiles (HIPVs), which play a significant role in indirect plant defences by guiding natural enemies to herbivores. However, these chemical signals are vulnerable to environmental stress. For instance, maize plants showed inconsistent emission patterns of (Z)-3hexenyl acetate and linalool under herbivory, influencing insect attraction (Block et al., 2018) [8] . Similarly, in potato plants, heat stress has been found to modify jasmonateregulated defence pathways, which in turn shifts both the timing and composition of herbivore-induced volatile emissions such as sesquiterpenes and green leaf volatiles (Zhong et al., 2024) [107] . The instability of HIPVs under climate stress has profound consequences for higher trophic levels, particularly parasitoids and predators. Ye et al. (2018) [100] demonstrated that in Spodoptera littoralis, herbivore-induced volatiles can modify caterpillar odours in ways that reduce their attractiveness to parasitoid Cotesia marginiventris, thereby creating unreliable cues that may confuse natural enemies. Drought stress further complicates this defence system. Research on Arabidopsis thaliana and other model plants subjected to water limitation revealed an increase in direct defences like phenolic compounds, while indirect defences reduced due to the disruption of volatilemediated parasitoid attraction (Lin et al., 2022) [54] . Beyond plant-herbivore dynamics, adverse weather conditions impair natural enemy foraging. Under combined humidity and temperature stress, Li et al. (2024) [106] found that interactions between Plutella xylostella (Diamondback moth) and its parasitoid Diadegma semiclausum were modified in both species-and age-dependent ways, showing how environmental variability directly affects parasitoid performance. Similarly, Vosteen et al. (2020) [87] reported that stormy weather reduced the odour-guided host-finding efficiency of parasitoids by disrupting their ability to detect key HIPVs like (E)-β-caryophyllene and indole. Together, these findings suggest that although plants may enhance biochemical resistance under stress, climate change destabilises HIPV-mediated communication, weakening indirect defences and threatening the stability of tri-trophic networks.

Plant-Pollinator Interactions

Pollinator attraction, another key link in the tri-trophic network, is highly affected by climate stress. Drought consistently reduces floral rewards, including nectar and pollen, lowering pollination success in both wild and crop systems (Waser and Price, 2016; Buchmann and Papaj, 2024) [12,94] . For instance, a decline in nectar sugars and amino acids directly impairs pollinator health. Apis mellifera and Bombus terrestris colonies show reduced survival and productivity when foraging in water-limited environments (Wilson Rankin et al., 2020) [96] . Quinanzoni et al. (2024) [70] further illustrated that urban and ornamental plants exposed to drought lose their visual appeal and olfactory cues, rendering them less attractive to pollinators. Air pollutants, particularly ozone (O₃), contribute further to disruption by breaking down essential floral volatiles like linalool, benzaldehyde, and (E)-β-ocimene. These substances are crucial chemical cues that lead pollinators such as Bombus terrestris and Apis mellifera to flower resources. Farré-Armengol et al. (2016) [23] and Fuentes et al. (2016) [26] showed that ozone reduces the stability of floral volatiles, breaking up odour plumes and making pollinators spend more time foraging while visiting fewer flowers. Extending this, Langford et al. (2023) [49] showed that polluted air masses distort floral odour trails, making them unreliable over long distances. Along with drought, climate stress weakens plant-pollinator communication, contributing to decline in pollinators, biodiversity loss, and reduced crop yields.

Interactive Stresses and Ecological Trade-offs

Environmental stressors rarely act in isolation but interact in complex and sometimes antagonistic ways. For example, drought can enhance direct volatile-mediated defences in plants while reducing their capacity to attract parasitoids, resulting in a trade-off between self-defence and guiding natural enemies (Lin et al., 2022) [54] . Likewise, Pinto-Zevallos and Blande (2024) [69] highlighted that climate change and air pollution are dual stressors that constrain plants' ability to coordinate defence and reproduction through volatile cues. From a broader ecological perspective, such disruptions exemplify how multi-species interactions are highly vulnerable to environmental stressors, with cascading consequences for biodiversity, ecosystem services, and agricultural stability (Strauss & Irwin, 2004) [81] . In addition to modifying plant signalling, climate stress directly affects insect physiology and behaviour, reshaping host-parasitoid dynamics. Waterman et al. (2024) [95] further demonstrated that HIPVs can propagate in rhythmic patterns among neighbouring plants, facilitating defence priming within plant communities, which may be interrupted during environmental extremes. These findings indicate that stress factors may restrict both within-plant and between-plant signalling at the same time, thereby diminishing the ecological reliability of tri-trophic interactions.

Case studies

Case study 1: Breaking Chemical Barriers: How Insects Detoxify Plant Defence Metabolites. According to Kshatriya et al. (2024) [44] , insect herbivores use detoxification enzymes from large gene families to overcome toxic plant metabolites. These enzymes function to functionalize toxins or conjugate them with polar substituents, reducing toxicity, increasing water solubility, and improving excretion. These enzymes are more abundant in generalists but also present in specialists. Insect microbiomes also play a role in detoxification, processing plant toxins. Detoxification gene families encode enzymes with broad substrate specificity, making insects adept at metabolising diverse plant toxins and synthetic insecticides.

Case study 2: Effects of Salt Stress on Aphid Development-Related Gene Expression and Secondary Metabolites in Cotton

A study conducted by Wang et al. (2015) [89] shows salt stress significantly impacts cotton's secondary metabolites, increasing the accumulation of substances like gossypol, flavonoids, and tannin. These substances are essential for plant defence against aphids and other insect pests. Aphid populations decrease with increased secondary metabolism, leading to gene expression modulation. Secondary metabolites like polyphenols, flavonoids, and alkaloids improve plant tolerance to salt stress and deter insect invasion. Salt stress also affects osmo-protectants like proline and soluble sugars, contributing to cotton stress tolerance and pest resistance.

Case study 3: Chemical Constraints and Coadaptation in

Insect-Plant Evolution Scriber (2002) [74] stated that coadaptations, chemical limitations, and phenotypic congruence influence the evolution of insect-plant relationships. Plant secondary chemicals constrain insect herbivores, shaping their feeding preferences and evolutionary pathways. Insect adaptation involves complex physiological and behavioural changes, while coevolution aligns insect sensory and metabolic traits with plant chemical profiles, resulting in ecological specialisation.

Case study 4: Dynamic Modulation of Arabidopsis Jasmonate Pathway during Insect Attack

Verhage et al. (2014) [86] recorded that the jasmonate signalling system in Arabidopsis is rewired during insect herbivory to optimise defence responses and minimise growth penalties. This complex network, involving pathways like salicylate and ethylene, fine-tunes plants' response to insect attack. Jasmonate signaling also orchestrates the production of defensive proteins and secondary metabolites, demonstrating the intricacy of plant defense mechanisms in biotic stress.

Implications for Agriculture and Pest Management

Climate-driven stresses such as heat, drought, and increased CO₂ will alter the biochemical composition of plants, which increases insect feeding and disrupts natural enemy regulation (Deutsch et al., 2018) [19] . These stress-induced changes can weaken the stability of traditional pest control approaches because herbivore resistance traits may be reduced while biocontrol efficiency declines (n et al., 2021; Nalam et al., 2021) [60] . Such shifts underline the necessity of integrating plant biochemical responses into future Integrated Pest Management (IPM) strategies. Abiotic stress leads to a decline in nitrogen levels and secondary defence compounds in plants, which will alter the growth and reproduction (Gupta et al., 2020; Smilanich et al., 2016) [29,79] . Stress conditions may also increase the tolerance of insecticides and interfere with induced plant defences, further complicating field management (Shrestha et al., 2023; Kumar et al., 2022) [78,47] . Therefore, it is critical to develop stress-resilient cultivars that are capable of maintaining metabolic defence pathways, such as phenolics, alkaloids, and terpenoids, even under climate extremes, which is becoming increasingly critical (Pandey & Pandey, 2020) [63] . [59,58,41] . Combined with biocontrol and cultural practices, priming offers a sustainable solution to reinforce crop resilience. These insights suggest that future agricultural systems must adopt biochemically informed IPM, in which breeding, biotechnology, and agroecological practices are aligned with the realities of climate stress and insect adaptation.

Future Directions

Future research should move beyond single-stress experiments and adopt multifactorial designs that reflect real field conditions, where heat, drought, elevated CO2 and nutrient limitations act simultaneously. Such approaches will provide more accurate predictions of how plant-insectnatural enemy interactions evolve under climate change (Jamieson et al., 2012; Lehmann et al., 2020) [38,52] . A second priority is the application of omics-based toolsincluding metabolomics, transcriptomics, proteomics, and genome editing-to unravel how plants dynamically regulate biochemical defence pathways under stress. These tools will help identify molecular markers that breeders can exploit to breed for stress-resilient and pest-tolerant cultivars (Pandey & Pandey, 2020) [64] . In particular, CRISPR/Cas-mediated editing of key genes involved in secondary metabolism offers novel opportunities for tailoring crop resistance traits in a climate-smart context (Zhu et al., 2020) [109] . Research should also expand its scope beyond herbivory, as parasitoids, pollinators, and soil-dwelling insects are also equally vulnerable to climate stress, and disruptions to their functions may alter ecosystem services and indirectly intensify pest outbreaks (Gillespie et al., 2016; Rasmann et al., 2014) [27,71] . Thus, a more holistic approach incorporating mutualists and natural enemies into experimental designs will be crucial for developing ecologically realistic pest management strategies. Another pressing direction is the integration of plant biochemical responses into pest forecasting and earlywarning systems. Current models primarily use temperaturedriven population dynamics, but coupling these with stressinduced changes in host quality, pest fitness, and natural enemy efficiency will improve their predictive accuracy (Deutsch et al., 2018) [19] . Such climate-adaptive pest models, remote sensing, and AI-driven decision support could guide real-time IPM decisions in farmers' fields. Finally, a systems-level approach that connects breeding, biotechnology, and agroecology is needed. Developing stress-resilient cultivars, deploying defence priming technologies, and reinforcing biological control must occur in tandem, guided by interdisciplinary research linking molecular biology, ecology, and climate science. This integrated strategy represents the most promising pathway to ensure sustainable pest management in the face of accelerating climate change.

Conclusion

Climate change is not only altering weather patterns but fundamentally reshaping the biochemical foundations of insect-plant interactions. Under climate stress, plants experience disruptions in primary metabolism, secondary defences, and signalling pathways, which diminish their resistance to herbivory. In response, insects evolve adaptive strategies such as enhanced enzymatic activity, detoxification, and sequestration, enabling them to exploit weakened hosts. These reciprocal shifts destabilise tritrophic interactions, undermining both natural pest suppression and pollination that are key pillars of agricultural productivity and ecosystem stability. For agriculture, this implies that conventional pest management approaches may prove increasingly inadequate under climate extremes. Addressing this challenge requires a multi-pronged strategy: breeding climate-resilient cultivars, employing biochemical defence priming, and integrating molecular, ecological, and agronomic knowledge within holistic IPM frameworks. By aligning molecular biology with environmental and agricultural practices, we can safeguard food security, sustain biodiversity, and ensure resilient agro-ecosystems in the face of accelerating climate change.

Disclaimer (artificial intelligence)

The author(s) hereby declare they have not used generative AI technologies such as Large Language Models (Chat GPT, COPILOT, etc.) and text-to-image generators while writing or editing manuscripts.

Acknowledgements

The Author(s) express their sincere gratitude to the Principal Scientist (Biochemistry), ARI, Rajendranagar, PJTAU, Hyderabad, and seniors for their enormous support.

Competing Interests

The author (s) declared that no conflict of interest exists.

References

1. Agati G, Azzarello E, Pollastri S, Tattini M. Flavonoids as antioxidants in plants: location and functional significance. Plant Sci. 2012;196:67-76.
2. Ainsworth EA, Long SP. What was synthesized from 15 years of free-air CO₂ enrichment (FACE)? New Phytol. 2005;165:351-372.
3. Arimura G, Matsui K, Takabayashi J. Chemical and molecular ecology of herbivore-induced plant volatiles: proximate factors and their ultimate functions. Plant Cell Physiol. 2009;50:911-923.
4. Barbehenn RV, Constabel CP. Tannins in plantherbivore interactions. Phytochemistry. 2011;72:15511565.
5. Belete T. Defence mechanisms of plants to insect pests: from morphological to biochemical approach. J Agric Sci Food Res. 2018;9(1):1-6.
6. Beran F, Petschenka G. Sequestration of plant defense compounds by insects: from mechanisms to insect-plant coevolution. Annu Rev Entomol. 2022;67(1):163-180.
7. Berenbaum M. Plant-herbivore interactions. In: Fox CW, Roff DA, Fairbairn DJ, editors. Evolutionary ecology: concepts and case studies. Oxford: Oxford University Press; 2001. p. 303-314.
8. Block AK, Hunter CT, Rering C, Christensen SA, Meagher RL. Contrasting insect attraction and herbivore-induced plant volatile production in maize. Planta. 2018;248(1):105-116.
9. Bloom AJ. Photorespiration and nitrate assimilation: a significant intersection between plant carbon and nitrogen. Annu Rev Plant Biol. 2015;66:191-216.
10. Booker F, Muntifering R, 20Grath M, Burkey K, Decoteau D, Fiscus E, et al. The ozone component of global change: interactions with plants and ecosystems. Plant Cell Environ. 2009;32:373-391.
11. Brower LP, Van Brower J, Corvino JM. Plant poisons in a terrestrial food chain. Proc Natl Acad Sci U S A. 1967;57(4):893-898.
12. Buchmann SL, Papaj DR. Hung out to dry: diminished flowers offer less to pollinators and us. New Phytol. 2024;244(3):746-748.
13. Castañeda LE, Figueroa CC, Fuentes-Contreras E, Niemeyer HM, Nespolo RF. Energetic costs of detoxification systems in herbivores feeding on chemically defended host plants: a correlational study in the grain aphid, Sitobion avenae. J Exp Biol. 2009;212(8):1185-1190.
14. Chamani M, Dadpour M, Dehghanian Z, Panahirad S, Chenari Bouket A, Oszako T, et al. From digestion to detoxification: exploring plant metabolite impacts on insect enzyme systems for enhanced pest control. Insects. 2025;16(4):392.
15. Chen CH. Detoxifying metabolism: detoxification enzymes. In: Xenobiotic metabolic enzymes: bioactivation and antioxidant defense. Cham: Springer International Publishing; 2020. p. 71-81.
16. Copolovici L, Kannaste A, Remmel T, Niinemets Ü. Volatile emissions from Alnus glutinosa induced by herbivory are quantitatively and qualitatively modified by drought. Stress Biol. 2014;61:123-132.
17. Couée I, Sulmon C, Gouesbet G, El Amrani A. Involvement of soluble sugars in reactive oxygen species balance and responses to oxidative stress in plants. J Exp Bot. 2006;57:449-459.
18. Dermauw W, Van Leeuwen T. The ABC gene family in arthropods: comparative genomics and role in insecticide transport and resistance. Insect Biochem Mol Biol. 2014;45:89-110.
19. Dicke M, Baldwin IT. The evolutionary context for herbivore-induced plant volatiles: beyond the 'cry for help'. Trends Plant Sci. 2010;15(3):167-175.
20. Engelberth J, Alborn HT, Schmelz EA, Tumlinson JH. Airborne signals prime plants against insect herbivore attack. Proc Natl Acad Sci U S A. 2004;101:1781-1785.
21. Erb M, Robert CA. Sequestration of plant secondary metabolites by insect herbivores: molecular mechanisms and ecological consequences. Curr Opin Insect Sci. 2016;14:8-11.
22. Farré-Armengol G, Peñuelas J, Li T, Yli-Pirilä P, Filella I, Llusia J, et al. Ozone degrades floral scent and reduces pollinator attraction to flowers. New Phytol. 2016;209(1):152-160.
23. Felton GW, Summers CB. Antioxidant systems in insects. Arch Insect Biochem Physiol. 1995;29(2):187197.
24. Fiscus EL, Booker FL, Burkey KO. Crop responses to ozone: uptake, modes of action, carbon assimilation and partitioning. Plant Cell Environ. 2005;28:997-1011.
25. Fuentes JD, Chamecki M, Roulston TA, Chen B, Pratt KR. Air pollutants degrade floral scents and increase insect foraging times. Atmos Environ. 2016;141:361374.
26. Gillespie MAK, Forrest JRK, Memmott J. The role of pollinator interactions in determining the resilience of plants to environmental change. Annu Rev Ecol Evol Syst. 2016;47:361-388.
27. Gouinguené S, Turlings TCJ. The effects of abiotic factors on induced volatile emissions in corn plants. Plant Physiol. 2002;129:1296-1307.
28. Gupta A, Rico-Medina A, Caño-Delgado AI. The physiology of plant responses to drought. Science. 2020;368(6488):266-269.
29. Hartmann T. From waste products to ecochemicals: fifty years of research on plant secondary metabolism. Phytochemistry. 2007;68:2831-2846.
30. Heidel-Fischer HM, Vogel H. Molecular mechanisms of insect adaptation to plant secondary compounds. Curr Opin Insect Sci. 2015;8:8-14.
31. Holopainen JK, Gershenzon J. Multiple stress factors and the emission of plant VOCs. Trends Plant Sci. 2010;15:176-184.
32. Howe GA, Jander G. Plant immunity to insect herbivores. Annu Rev Plant Biol. 2008;59:41-66.
33. Howe GA, Jander G. Plant immunity to insect herbivores. Annu Rev Plant Biol. 2008;59:41-66.
34. Hu B, Zhang SH, Ren MM, Tian XR, Wei Q, Mburu DK, et al. The expression of Spodoptera exigua P450 and UGT genes: tissue specificity and response to insecticides. Insect Sci. 2019;26(2):199-216.
35. Jactel H, Koricheva J, Castagneyrol B. Responses of forest insect pests to climate change: not so simple. Curr Opin Insect Sci. 2021;47:93-100.
36. Jamieson MA, Trowbridge AM, Raffa KF, Lindroth RL. Consequences of climate warming and altered precipitation patterns for plant-insect and multitrophic interactions. Plant Physiol. 2012;160(4):1719-1727.
37. Jamieson MA, Trowbridge AM, Raffa KF, Lindroth RL. Consequences of climate warming and altered precipitation patterns for plant-insect and multitrophic interactions. Plant Physiol. 2012;160(4):1719-1727.
38. Jeckel AM, Beran F, Züst T, Younkin G, Petschenka G, Pokharel P, et al. Metabolization and sequestration of plant specialized metabolites in insect herbivores: current and emerging approaches. Front Physiol. 2022;13:1001032.
39. Karban R, Agrawal AA. Herbivore offense. Annu Rev Ecol Syst. 2002;33:641-664.
40. Kaur H, Devi R, Gupta S, Bhardwaj R. RNA-based sprays: a novel strategy for crop protection under climate change scenarios. Front Plant Sci. 2023;14:1165432.
41. Khan MIR, Iqbal N, Masood A, Per TS, Khan NA. Role of salicylic acid in heat stress tolerance in plants. Plant Signal Behav. 2015;10:e1000140.
42. Krasensky J, Jonak C. Drought, salt, and temperature stress-induced metabolic rearrangements and regulatory networks. J Exp Bot. 2012;63:1593-1608.
43. Kshatriya K, Gershenzon J. Disarming the defenses: insect detoxification of plant defense-related specialized metabolites. Curr Opin Plant Biol. 2024;81:102577. International Journal of Advanced Biochemistry Research https://www.biochemjournal.com
44. Kshatriya K, Gershenzon J. Disarming the defenses: insect detoxification of plant defense-related specialized metabolites. Curr Opin Plant Biol. 2024;81:102577.
45. Kshatriya K, Gershenzon J. Disarming the defenses: insect detoxification of plant defense-related specialized metabolites. Curr Opin Plant Biol. 2024;81:102577.
46. Kumar S, Rani A, Bishnoi R. Abiotic stress-mediated interactions between insect pests and plants: implications for pest management. Physiol Mol Biol Plants. 2022;28(9):1579-1590.
47. Kutty NN, Mishra M. Dynamic distress calls: volatile infochemicals induce and regulate defense responses during herbivory. Front Plant Sci. 2023;14:1135000.
48. Langford B, Ryalls JM, Mullinger NJ, Hayden P, Nemitz E, Pfrang C, et al. Mapping the effects of ozone pollution and mixing on floral odour plumes and their impact on plant-pollinator interactions. Environ Pollut. 2023;336:122336.
49. Leakey ADB, Ainsworth EA, Bernacchi CJ, Rogers A, Long SP, Ort DR. Elevated CO₂ effects on plant carbon, nitrogen, and water relations. Plant Cell Environ. 2009;32:1103-1121.
50. Lehmann P, Ammunét T, Barton M, Battisti A, Eigenbrode SD, Jepsen JU, Kalinkat G, Neuvonen S, Niemelä P, Terblanche JS, Økland B. Complex responses of global insect pests to climate warming. Front Ecol Environ. 2020;18(3):141-150.
51. Lehmann P, Ammunét T, Barton M, Battisti A, Eigenbrode SD, Jepsen JU, et al. Complex responses of global insect pests to climate warming. Front Ecol Environ. 2020;18(3):141-150.
52. Li D, Brough B, Rees JW, Coste CF, Yuan C, Fowler MS, et al. Humidity modifies species-specific and age-dependent heat stress effects in an insect host-parasitoid interaction. Ecol Evol. 2024;14(7):e70047.
53. Lin PA, Paudel S, Bin Zainuddin N, Tan CW, Helms A, Ali JG, et al. Low water availability enhances volatile-mediated direct defences but disturbs indirect defences against herbivores. J Ecol. 2022;110(11):2759-2771.
54. Loreto F, Schnitzler JP. Abiotic stresses and induced BVOCs. Trends Plant Sci. 2010;15:154-166.
55. Ma H. Effect of salt stress on secondary metabolites of cotton and its relationship to pest resistance. J Agric Sci. 2021;13(4):45-53.
56. Malcolm SB. Milkweeds, monarch butterflies and the ecological significance of cardenolides. Chemoecology. 1994;5(3):101-117.
57. Martinez-Medina A, Flors V, Heil M, Mauch-Mani B, Pieterse CMJ, Pozo MJ, et al. Recognizing plant defence priming. Trends Plant Sci. 2022;27(9):808-82
58. Mauch-Mani B, Baccelli I, Luna E, Flors V. Defence priming: an adaptive part of induced resistance. Annu Rev Plant Biol. 2017;68:485-512.
59. Nalam VJ, Louis J, Shah J. Plant defense against aphids, the pest extraordinaire. Plant Sci. 2021;313:111016.
60. Nishida R. Sequestration of defensive substances from plants by Lepidoptera. Annu Rev Entomol. 2002;47(1):57-92.
61. Opitz SE, Müller C. Plant chemistry and insect sequestration. Chemoecology. 2009;19(3):117-154.
62. Pandey P, Pandey V. Plant secondary metabolites and resilience under climate stress. J Appl Bot Food Qual. 2020;93:118-126.
63. Pandey P, Pandey V. Plant secondary metabolites and resilience under climate stress. J Appl Bot Food Qual. 2020;93:118-126.
64. Pell EJ, Schlagnhaufer CD, Arteca RN. Ozone-induced oxidative stress: mechanisms of action and reaction. Physiol Plant. 1997;100:264-273.
65. Peñuelas J, Estiarte M. Can elevated CO₂ affect secondary metabolism and ecosystem function? Trends Ecol Evol. 1998;13:20-24.
66. Peñuelas J, Llusià J. BVOCs under global change. Trends Plant Sci. 2003;8:105-109.
67. Peñuelas J, Staudt M. BVOCs and global change. Trends Plant Sci. 2010;15:133-144.
68. Pinto-Zevallos DM, Blande JD. Challenges of climate change and air pollution for volatile-mediated plantparasitoid signalling. Curr Opin Insect Sci. 2024;66:101290.
69. Quinanzoni M, Marcolet D, Michelot-Antalik A. Drought response and urban-pollinator attractiveness of ornamental plant species. Basic Appl Ecol. 2024;78:113.
70. Rasmann S, Pellissier L, Defossez E, Jactel H, Kunstler G. Climate-driven change in plant-insect interactions along elevation gradients. Funct Ecol. 2014;28(1):4654.
71. Rasmann S, Pellissier L, Defossez E, Jactel H, Kunstler G. Climate-driven change in plant-insect interactions along elevation gradients. Funct Ecol. 2014;28(1):4654.
72. Schoonhoven LM, van Loon JJA, Dicke M. InsectPlant Biology. 2nd ed. Oxford: Oxford University Press; 2005.
73. Scriber JM. Evolution of insect-plant relationships: chemical constraints, coadaptation and concordance of insect/plant traits. Entomol Exp Appl. 2002;104(1):217235.
74. Scriber JM. Evolution of insect-plant relationships: chemical constraints, coadaptation and concordance of insect/plant traits. Entomol Exp Appl. 2002;104(1):217235.
75. Scudder GGE, Meredith J. The permeability of the midgut of three insects to cardiac glycosides. J Insect Physiol. 1982;28(8):689-694.
76. Sharma A, Jha AB, Dubey RS, Pessarakli M. Jasmonic acid in plant abiotic stress tolerance. J Plant Growth Regul. 2013;32:237-245.
77. Shrestha A, Nepal MP, Maharjan S. Plant stress and insect pest outbreaks: a review. Front Agron. 2023;5:1123456.
78. Smilanich AM, Fincher RM, Dyer LA. Does plant apparency matter? Thirty years of data provide limited support but reveal clear patterns of the effects of plant chemistry on herbivores. New Phytol. 2016;210(3):1044-1057.
79. Strauss AS, Peters S, Boland W, Burse A. ABC transporter functions as a pacemaker for sequestration of plant glucosides in leaf beetles. Elife. 2013;2:01096.
80. Strauss SY, Irwin RE. Ecological and evolutionary consequences of multispecies plant-animal interactions. Annu Rev Ecol Evol Syst. 2004;35:435-466.
81. Suzuki N, Rivero RM, Shulaev V, Blumwald E, Mittler R. Abiotic and biotic stress combinations. New Phytol. 2014;203:32-43.
82. Taub DR, Wang X. Why are nitrogen concentrations in plant tissues lower under elevated CO₂? A critical examination of the hypotheses. J Integr Plant Biol. 2008;50:1365-1374.
83. Turlings TC, Erb M. Tritrophic interactions mediated by herbivore-induced plant volatiles: mechanisms, ecological relevance, and application potential. Annu Rev Entomol. 2018;63:433-452.
84. Van Dam NM, Heil M. Jasmonate-mediated plant responses to insect herbivory. New Phytol. 2011;189(3):988-1000.
85. Verhage A, Vlaardingerbroek I, Raaymakers C, Van Dam NM, Dicke M, Van Wees SCM, et al. Rewiring of the jasmonate signaling pathway in Arabidopsis during insect herbivory. Front Plant Sci. 2014;5:306.
86. Vosteen I, Bianchi FJ, Poelman EH. Adverse weather conditions impede odor-guided foraging of parasitoids and reduce their host-finding success. Agric Ecosyst Environ. 2020;301:107066.
87. Vuorinen T, Nerg AM, Holopainen JK. Ozone exposure triggers the emission of herbivore-induced plant volatiles in Brassica nigra. Plant Cell Environ. 2004;27:1225-1232.
88. Wang Q, Eneji AE, Kong X, Wang K, Dong H. Salt stress effects on secondary metabolites of cotton in relation to gene expression responsible for aphid development. PLoS One. 2015;10(6):e0129541.
89. Wang Q, Eneji AE, Kong X, Wang K, Dong H. Salt stress effects on secondary metabolites of cotton in relation to gene expression responsible for aphid development. PLoS One. 2015;10(6):e0129541.
90. Wang Y, Baumdicker F, Schweiger P, Kuenzel S, Staubach F. Horizontal gene transfer-mediated bacterial strain variation affects host fitness in Drosophila. BMC Biol. 2021;19(1):187.
91. War AR, Taggar GK, Hussain B, Taggar MS, Nair RM, Sharma HC. Plant defence against herbivory and insect adaptations. AoB Plants. 2018;10(4):037.
92. War AR, Taggar GK, Hussain B, Taggar MS, Nair RM, Sharma HC. Plant defence against herbivory and insect adaptations. AoB Plants. 2018;10(4):ply037.
93. Waser NM, Price MV. Drought, pollen and nectar availability, and pollination success. Ecology. 2016;97(6):1400-1409.
94. Waterman JM, Cofer TM, Wang L, Glauser G, Erb M. High-resolution kinetics of herbivore-induced plant volatile transfer reveal clocked response patterns in neighboring plants. Elife. 2024;12:RP89855.
95. Wilson Rankin EE, Barney SK, Lozano GE. Reduced water negatively impacts social bee survival and productivity via shifts in floral nutrition. J Insect Sci. 2020;20(5):15.
96. Yalpani N, Enyedi AJ, León J, Raskin I. Ozonesensitive tobacco and regulation of salicylic acid biosynthesis. Plant Physiol. 1994;105:467-474.
97. Yang Z, Deng M, Wang W, Xiao T, Huang X, Zhao X, et al. Exploring the adaptation mechanism of Spodoptera litura to xanthotoxin: insights from transcriptional responses and CncC signaling pathwaymediated UGT detoxification. Insect Biochem Mol Biol. 2025;177:104259.
98. Yang Z, Deng M, Wang W, Xiao T, Huang X, Zhao X, et al. Exploring the adaptation mechanism of Spodoptera litura to xanthotoxin: insights from transcriptional responses and CncC signaling pathwaymediated UGT detoxification. Insect Biochem Mol Biol. 2025;177:104259.
99. Ye M, Veyrat N, Xu H, Hu L, Turlings TC, Erb M. An herbivore-induced plant volatile reduces parasitoid attraction by changing the smell of caterpillars. Sci Adv. 2018;4(5):eaar4767.
100. Zalucki MP, Brower LP, Alonso-M A. Detrimental effects of latex and cardiac glycosides on survival and growth of first-instar monarch butterfly larvae Danaus plexippus feeding on the sandhill milkweed Asclepias humistrata. Ecol Entomol. 2001;26(2):212-224.
101. Zavala JA, Casteel CL, DeLucia EH, Berenbaum MR. Impact of global change on herbivory. Annu Rev Entomol. 2013;58:79-97.
102. Zavala JA, Casteel CL, DeLucia EH, Berenbaum MR. Rising atmospheric CO₂ and the impact on plant-insect interactions. Plant Signal Behav. 2008;3:144-146.
103. Zavala JA, Nabity PD, DeLucia EH. An emerging understanding of mechanisms governing insect herbivory under elevated CO₂. Annu Rev Entomol. 2017;62:57-80.
104. Zavala JA, Nabity PD, DeLucia EH. How elevated CO₂ and global warming may affect herbivore-plant interactions. Ann N Y Acad Sci. 2017;1389:138-154.
105. Zhang A, Liang K, Yuan L, Li T, Jiang D, Yan S. Insect adaptation: unveiling the physiology of digestion in challenging environments. Chem Biol Technol Agric. 2024;11(1):129.
106. Zhong J, Zhang J, Zhang Y, Ge Y, He W, Liang C, et al. Heat stress reprograms herbivory-induced defense responses in potato plants. BMC Plant Biol. 2024;24(1):677.
107. Zhou R, Yu X, Kjaer KH, Rosenqvist E, Ottosen C-O, Wu Z. Elevated CO₂ alters defence signalling in Arabidopsis thaliana against Spodoptera litura. Front Plant Sci. 2019;10:906.
108. Zhu H, Li C, Gao C. Applications of CRISPR-Cas in agriculture and plant biotechnology. Nat Rev Mol Cell Biol. 2020;21(11):661-677.