Elevated temperatures, persisting beyond a threshold, inflict irreversible harm on plant growth and development, inducing various physiological and biochemical changes. These alterations affect fundamental processes like photosynthesis, water regulation, internal hormone levels, and the synthesis of primary and secondary metabolites, ultimately impairing crop yield significantly.
The impact of high temperatures on plants is profound, disrupting growth, physiological functions, and metabolic pathways. Escalating temperatures pose a severe threat to crop production, causing substantial reductions in yield. At a molecular level, heat stress disrupts photosynthesis efficiency, shortens plant life cycles, and hampers yield. It also hampers respiratory enzyme activity, leading to energy deficits. Heat-induced movement of macromolecules can upset membrane stability, altering permeability and fluidity and resulting in the leakage of ions and amino acids. Phenotypes of heat stress encompass slowed growth, wilting during vegetative stages, and issues like reduced pollen vitality, abnormal fertilization, and poor grain filling during reproductive stages.
High-temperature stress triggers changes in plant metabolome. For instance, GSA1, responsible for redirecting metabolic flux in lignin biosynthesis toward flavonoid biosynthesis, aids in accumulating flavonoids and anthocyanins, mitigating heat-induced damage. Similarly, HsfB1 influences pathways like phenylpropanoid and flavonoid pathways, linking stress responses to physiological development in tomatoes. The intricate interaction between Hsf and metabolites proves pivotal for corn's heat tolerance. Heat induces the expression of ZmHSFA2, which, in its active trimer form, enhances raffinose biosynthesis by activating ZmGOLS2 and ZmRAFS, thereby regulating heat tolerance.
In a recent publication titled 'The miR156b-GmSPL2b module mediates male fertility regulation of cytoplasmic male sterility-based restorer line under high-temperature stress in soybean,' Professor Yang from the National Soybean Improvement Center at Nanjing Agricultural University elucidated the molecular mechanism behind miR156b-GmSPL2b's role in regulating male fertility in soybean CMS restorer lines under high-temperature stress. This study, employing transcriptomics and metabolomics provided by MetWarebio, delves into the critical role of miR156b-GmSPL2b in soybean's response to high-temperature stress, especially during flowering and seedling stages. High temperatures can jeopardize soybean flowering and fertilization, severely impacting its development.
The research employed transcriptome sequencing to analyze miR156b overexpression lines (miR156bOE) and control groups (W82) under normal and high-temperature conditions. The findings revealed over 3500 differentially expressed genes (DEGs) in anthers under high-temperature stress in both miR156bOE and W82 compared to normal temperature conditions. Additionally, extensive targeted metabolomics studies detected 1026 metabolites in the anthers, with approximately 243 metabolites showing significant differences under high-temperature stress. Notably, flavonoids analysis constituted the most abundant class of metabolites, with distinct variations observed in response to high temperatures.
The study delineates the pivotal role of the miR156b-GmSPL2b module in regulating male fertility in soybean CMS restorer lines under high-temperature stress. It proposes a model wherein miR156b governs male fertility by controlling GmSPL2b, subsequently influencing downstream regulatory genes associated with carbon metabolism, sugar transport, and ROS clearance. Target genes like GmSPL4a/b might also contribute to this mechanism. Future investigations could explore precise miR156b binding sites in GmSPL2b or harness genes within the miR156b-GmSPL2b pathway to enhance fertility and develop heat-tolerant soybean varieties.