Research article · 2024 · Full text
International Journal of Advanced Biochemistry ResearchEnhancing rice resilience to zinc deficiency: Insights from leaf and seed zinc accumulation, glutathione reductase activity and hydrogen peroxide
Volume 8(1S) · Pages 435–439 · DOI: 10.33545/26174693.2024.v8.i1sg.366 ↗
Research areasPlant Micronutrient Interactions and EffectsAgricultural Science and FertilizationAluminum toxicity and tolerance in plants and animals
Abstract
Author-writtenThe experiment was conducted to investigate the responses of two rice genotypes, IR 74 (sensitive) and RIL 46 (efficient), to zinc deficiency. Grown in both field and controlled conditions, the experiment aimed to understand the physiological and biochemical factors influencing their responses for developing zinc-efficient rice varieties. Under normal zinc conditions, both genotypes exhibited superior root systems, but zinc deficiency hindered root growth, more so in IR 74. RIL 46 showed enhanced zinc uptake and translocation under both conditions, maintaining higher zinc content in grains. Glutathione Reductase (GR) enzyme activity in leaves revealed a strategic response in RIL 46 to mitigate oxidative damage under zinc deficiency. Hydrogen peroxide accumulation in roots indicated a heightened oxidative stress response in the sensitive line. In conclusion, RIL 46 demonstrated genetic resilience to zinc deficiency, emphasizing the importance of zinc accumulation, GR activity and hydrogen peroxide levels as indicators for selecting resilient rice varieties in zinc-limiting environments.
Summary
Source-checkedPlain-language reading of the full paper, prepared with AI and checked against the text. Each point links to the authors' own words.
Why it matters
- Zinc is a critical micronutrient for plants, supporting various biochemical and physiological functions. View evidence ↗
- Zinc deficiency is a major global health concern, affecting approximately two billion people according to the WHO. View evidence ↗
- Rice is a primary calorie source for many, especially in Asia, but it is often deficient in micronutrients like zinc. View evidence ↗
The question
- The study aimed to identify the physiological and biochemical factors that allow certain rice varieties to be more efficient with zinc to aid breeding programs. View evidence ↗
What they did
- The researchers compared two rice genotypes: IR 74, which is sensitive to zinc deficiency, and RIL 46, which is tolerant. View evidence ↗
- Plants were grown in both field and controlled phytotron environments, with groups receiving either zinc (+Zn) or no zinc (-Zn). View evidence ↗
What they found
- Zinc deficiency hindered root growth in both genotypes, but the sensitive IR 74 variety was more severely affected than RIL 46. View evidence ↗
- The tolerant RIL 46 variety maintained higher zinc uptake under deficient conditions compared to IR 74. View evidence ↗
- The sensitive rice line accumulated more hydrogen peroxide in its roots under zinc deficiency, indicating a higher oxidative stress response. View evidence ↗
What it means
- The authors conclude that zinc accumulation in leaves/seeds, GR activity, and hydrogen peroxide levels are effective indicators for selecting zinc-resilient rice varieties. View evidence ↗
Visual summary
1 visualsIllustrations explain the paper; they do not show study data.
Oxidative Stress Response Comparison
AI-generated conceptual illustration (rice plants (Oryza sativa)). It explains the idea and does not show study data.
View source evidence ↗Figures & tables
From the original paper
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Figure 9Introduction
Zinc (Zn) is an essential micronutrient for plants, plays a crucial role in various physiological and biochemical processes. Zinc is involved in a wide range of biological functions in plants and humans including serving as a cofactor for numerous enzymes, maintaining the structure of proteins and playing a role in gene expression (Costa et al., 2023 & Roohani et al., 2013) [4, 5] . The World Health Organization (WHO) estimates that around two billion people worldwide suffer from Zn deficiency. Zinc deficiency is indeed a significant global health issue, particularly in developing countries. One of the primary reasons for zinc deficiency in many populations is the consumption of diets that are low in zinc (Hussain et al., 2022) [6] , particularly in regions where people rely heavily on plant-based foods. And also due to inadequate Zn availability in soils which reduces yield and nutrient content in grains (Saleem et al., 2022) [7] . One of the best strategies is to focus on identifying and developing plant varieties that are efficient in taking up and utilizing zinc from the soil and produce Zn dense grains by selecting the parental lines with desirable traits through breeding programmes (Khan et al., 2022) [8] . Rice is a major staple food for a significant portion of the world's population, particularly in Asia where it serves as a primary source of calories. However, rice is known to be deficient in certain micronutrients, including zinc (Gindri et al., 2020) [9] . Identifying Zn efficient rice genotypes by understanding their physiological, biochemical and molecular mechanism is a best option combat the Zn deficiency both in plants and humans. The response of rice plants to zinc deficiency can vary based on genetic, physiological and biochemical factors. Among biochemical aspects, glutathione reductase plays a crucial role in enhancing plant tolerance to abiotic stresses. Similarly, plants overproduce reactive oxygen species like hydrogen peroxide (H 2 O 2 ) during abiotic stresses and hence, regulation of Glutathione Reductase and H 2 O 2 is vital for imparting stress tolerance in plants (Hasanuzzaman et al., 2017) [10] . An experiment was conducted in two contrasting rice genotypes to investigate their varied responses to zinc deficiency. The goal was to study the physiological and biochemical factors influencing these responses, providing valuable insights for the development of zinc-efficient rice varieties through breeding programs further to improve crop productivity and nutritional quality under zinc-limiting conditions.
Materials and Methods
For the experiment, two contrasting Zn deficient efficient rice varieties, IR 74 (sensitive) and RIL 46 (tolerant) developed at IRRI, Philippines were grown. One set was grown in the field condition and other set was grown in phytotron facility (controlled environment). In both the conditions one set of plants were maintained with Zn and another set was without Zn (Fig. 1). In the experiment, the "+Zn" plot received 15 kg per hectare of zinc in the form of ZnSO 4 •7H 2 O in addition to recommended dose of nitrogen, phosphorous and potassium, while the "-Zn" plot received no zinc. The seeds of rice varieties IR74 and RIL46 were sown in shallow seedling trays filled with untreated soil and after three weeks, the seedlings were transplanted as single-plant hills in microplots measuring 2.4 m 2 with randomized complete block design with three replications. Similarly, pre-germinated seeds were sown in plastic trays maintained at phytotron (Fig. 2). Trays were filled with culture solution which contained 0.35g ZnSO 4 .7H 2 O per 10 L of distilled water along with other required elements. For "-Zn", culture solution was prepared without ZnSO 4 .7H 2 O (Singh & Mishra, 2004) [3] , modified from Yoshida et al., 1976 [2] . Thirty days after transplanting, observations on physiological parameters were recorded. Root and shoot length were measured (data not shown). Plants were pulled from the soil and the nutrient solution without damaging roots for Zn estimation, glutathione reductase activity and Hydrogen peroxide accumulation. After harvest Zn content in seeds were estimated in IR 74 and RIL 46 at "+Zn" and "-Zn" condition. Samples were collected for Zn estimation, enzyme (glutathione reductase) analysis and root staining for hydrogen peroxide accumulation both in Zn efficient and sensitive lines and the data presented in the paper are from the plants grown in the field condition. The samples were washed with Nanopure quality water, wrapped in aluminium foils and were snap-frozen in liquid nitrogen (Fig. 3). The collected samples were stored at -80 °C refrigerator until measurements were done. Zinc estimation in root, shoot and grains Finely powdered sample of root, leaves and grains (500 mg) were taken into polyethylene tubes, to which 25 ml 1N HCL solution was added and homogenized once the solution along with the powder. The sample was left over night for 24 hrs, without shaking by allowing it to digest in acid. The following day, once again the solution was mixed by shaking before filtering. The extract was collected in clean (acid washed) polyethylene tube. Observations of the sample extract were recorded using Atomic Absorption Spectrophotometer.
Estimation of glutathione reductase activity
The assessment of glutathione reductase (GR) enzyme activity, as well as protein and GR content, was conducted following the protocol outlined by Halliwell and Foyer in 1978.
Hydrogen peroxide accumulation in roots of sensitive and efficient genotypes
The roots of both Zn-sensitive and Zn-efficient lines were subjected to staining with CM-H2DCFDA (Chao et al., 2008) [11] and subsequently observed for the accumulation of hydrogen peroxide (H 2 O 2 ) using a fluorescence microscope with excitation at 488nm and emission in the range of 510-560nm, with a bandpass filter set at 510-530nm. The zinc content analysis in leaves conducted 30 days after transplanting revealed that while IR 74 exhibited a notable capacity to absorb and translocate more zinc under normal zinc conditions ("+Zn"), its ability to uptake and translocate zinc was compromised in the absence of zinc (Fig 6). In contrast, RIL 46 demonstrated a higher zinc uptake even under zinc-deficient conditions, surpassing the susceptible variety IR 74. This highlights RIL 46's enhanced resilience to zinc deficit conditions compared to IR 74. Zn content analysis in grains post-harvest revealed distinct patterns (Fig 7). Under normal Zn conditions ("+Zn"), RIL accumulated 0.0235% zinc, outperforming IR 74, which accumulated 0.0195% Zn. In the absence of Zn, IR 74 showed a significant decrease in zinc accumulation, reaching only 0.013% zinc. In contrast, the efficient line, RIL 46, maintained a higher Zn content even under zinc stress conditions, recording 0.0204% zinc. This underscores the resilience of the efficient line to zinc stress, as evidenced by its sustained zinc accumulation compared to the susceptible variety IR 74. In the context of this study, the investigation into Glutathione Reductase (GR) enzyme activity in leaves revealed that under normal conditions, both the sensitive and efficient lines exhibited comparable GR enzyme activity levels (Fig 8). However, when subjected to zinc deficit conditions, a noteworthy divergence in GR activity became apparent. The efficient line displayed significantly lower GR activity compared to the sensitive line. This observed reduction in GR activity in the efficient line under zinc deficit conditions can be attributed to a strategic response to mitigate oxidative damage. Despite the zinc deficiency stress, the efficient line demonstrated less oxidative damage, as evidenced by the lower GR activity.
Results and Discussion
This suggests that the efficient line has developed mechanisms to cope with zinc deficit-induced oxidative stress more efficiently. Conversely, the sensitive line exhibited higher GR activity under zinc deficit conditions. This heightened enzymatic activity can be interpreted as a reactive response to counteract increased oxidative damage experienced by the sensitive line in the absence of sufficient zinc. The elevated GR activity in the sensitive line signifies an attempt to mitigate the oxidative stress and underscores the susceptibility of this line to the adverse effects of zinc deficiency.
Conclusion
The study suggests that the accumulation of zinc in leaves and seeds, along with Glutathione Reductase activity and hydrogen peroxide accumulation, can serve as valuable indicators for selecting rice lines that exhibit resilience and better adaptation to zinc deficit soil conditions. These parameters provide insights into the plant's ability to cope with nutrient stress, aiding in the identification and cultivation of varieties that can thrive under zinc-deficient environments.
Figures and tables from the paper
References
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