School of Agriculture, Food and Ecosystem Sciences (SAFES), Faculty of Science, The University of Melbourne, Parkville, VIC, 3010, Australia.
BMC Plant Biol. 2023 Oct 17;23(1):498. doi: 10.1186/s12870-023-04492-5.
Lentil is an essential cool-season food legume that offers several benefits in human nutrition and cropping systems. Drought stress is the major environmental constraint affecting lentil plants' growth and productivity by altering various morphological, physiological, and biochemical traits. Our previous research provided physiological and biochemical evidence showing the role of silicon (Si) in alleviating drought stress in lentil plants, while the molecular mechanisms are still unidentified. Understanding the molecular mechanisms of Si-mediated drought stress tolerance can provide fundamental information to enhance our knowledge of essential gene functions and pathways modulated by Si during drought stress in plants. Thus, the present study compared the transcriptomic characteristics of two lentil genotypes (drought tolerant-ILL6002; drought sensitive-ILL7537) under drought stress and investigated the gene expression in response to Si supplementation using high-throughput RNA sequencing.
This study identified 7164 and 5576 differentially expressed genes (DEGs) from drought-stressed lentil genotypes (ILL 6002 and ILL 7537, respectively), with Si treatment. RNA sequencing results showed that Si supplementation could alter the expression of genes related to photosynthesis, osmoprotection, antioxidant systems and signal transduction in both genotypes under drought stress. Furthermore, these DEGs from both genotypes were found to be associated with the metabolism of carbohydrates, lipids and proteins. The identified DEGs were also linked to cell wall biosynthesis and vasculature development. Results suggested that Si modulated the dynamics of biosynthesis of alkaloids and flavonoids and their metabolism in drought-stressed lentil genotypes. Drought-recovery-related DEGs identified from both genotypes validated the role of Si as a drought stress alleviator. This study identified different possible defense-related responses mediated by Si in response to drought stress in lentil plants including cellular redox homeostasis by reactive oxygen species (ROS), cell wall reinforcement by the deposition of cellulose, lignin, xyloglucan, chitin and xylan, secondary metabolites production, osmotic adjustment and stomatal closure.
Overall, the results suggested that a coordinated interplay between various metabolic pathways is required for Si to induce drought tolerance. This study identified potential genes and different defence mechanisms involved in Si-induced drought stress tolerance in lentil plants. Si supplementation altered various metabolic functions like photosynthesis, antioxidant defence system, osmotic balance, hormonal biosynthesis, signalling, amino acid biosynthesis and metabolism of carbohydrates and lipids under drought stress. These novel findings validated the role of Si in drought stress mitigation and have also provided an opportunity to enhance our understanding at the genomic level of Si's role in alleviating drought stress in plants.
小扁豆是一种重要的冷季食用豆科植物，在人类营养和种植系统中具有多种益处。干旱胁迫是影响小扁豆植物生长和生产力的主要环境限制因素，它通过改变各种形态、生理和生化特性来实现。我们之前的研究提供了生理和生化证据，表明硅（Si）在缓解小扁豆植物干旱胁迫方面的作用，而其分子机制仍未确定。了解 Si 介导的耐旱性的分子机制可以为增强我们对 Si 在植物干旱胁迫下调节必需基因功能和途径的基本信息提供基础。因此，本研究比较了两个小扁豆基因型（耐旱性-ILL6002；耐旱性-ILL7537）在干旱胁迫下的转录组特征，并使用高通量 RNA 测序研究了 Si 补充对基因表达的影响。
本研究从小扁豆基因型（ILL6002 和 ILL7537）在 Si 处理下的干旱胁迫中分别鉴定了 7164 和 5576 个差异表达基因（DEGs）。RNA 测序结果表明，Si 处理可改变两种基因型在干旱胁迫下与光合作用、渗透保护、抗氧化系统和信号转导相关的基因表达。此外，这两种基因型的这些 DEGs 还与碳水化合物、脂质和蛋白质的代谢有关。鉴定出的 DEGs 还与细胞壁生物合成和脉管系统发育有关。结果表明，Si 调节了干旱胁迫下小扁豆基因型中生物碱和类黄酮的生物合成及其代谢的动态变化。从小扁豆基因型中鉴定出的与干旱恢复相关的 DEGs 验证了 Si 作为干旱胁迫缓解剂的作用。本研究确定了 Si 介导的响应干旱胁迫的不同可能防御反应，包括活性氧（ROS）引起的细胞氧化还原稳态、纤维素、木质素、木葡聚糖、几丁质和木聚糖的沉积引起的细胞壁加固、次生代谢产物的产生、渗透调节和气孔关闭。
总的来说，结果表明，Si 诱导耐旱性需要各种代谢途径的协调相互作用。本研究鉴定了参与 Si 诱导的小扁豆植物耐旱性的潜在基因和不同防御机制。Si 处理在干旱胁迫下改变了光合作用、抗氧化防御系统、渗透平衡、激素生物合成、信号转导、氨基酸生物合成以及碳水化合物和脂质代谢等各种代谢功能。这些新发现验证了 Si 在缓解干旱胁迫方面的作用，并为我们在基因组水平上理解 Si 在缓解植物干旱胁迫方面的作用提供了机会。
