Plant Physiology and Biochemistry最新文献

This study demonstrates the impact of combined (drought and high light) stress on thylakoid organization in Pea, Pisum sativum. The combined stress significantly reduced gas exchange parameters, indicating compromised photosynthetic activity. Chlorophyll a fluorescence analysis confirmed a decrease in the photochemical efficiency of photosystem (PS)II. This was accompanied by alterations in thylakoid macro-organization, specifically a reduction in PSII-light-harvesting complex (LHC)II supercomplexes and PSII dimers, coupled with an increase in LHCII monomers. This pattern indicates a redistribution of LHCII from tightly assembled PSII supercomplexes into monomeric forms, reflecting a stress-induced disassembly of the antenna system. In response to the combined stress, the plants exhibited photoprotective mechanisms, including increased carotenoid content, accompanied by decreased chlorophyll content. Additionally, elevated reactive oxygen species were observed, likely as a consequence of the stress combination, which contributed to the thylakoid membrane disorganization and a subsequent decline in membrane protein content. The plants also activated protective mechanisms such as increased non-photochemical quenching and elevated PSBS (PS II subunit S) protein levels to mitigate photoinhibition. Furthermore, the thylakoid stacks displayed a looser arrangement under combined stress, potentially due to the observed changes in thylakoid supercomplexes. Both PSI and PSII were equally affected, showing a reduced abundance of proteins under combined stress. Simultaneously, the abundance of antioxidant proteins increased, reflecting the plant's attempt to counteract the oxidative stress.

Plants encounter various environmental challenges like drought and salinity, which disrupt their physiological and biochemical functions and adversely impact growth, development, and overall plant productivity. To counter these challenges, plants deploy various strategies, including modulation of plant growth regulators (PGR), which play a vital role in impacting plant performance under optimum and/or stress conditions. Melatonin (MT), a PGR is known to perform multifaceted functions in plants throughout their lifecycle, from seed germination to fruit development, and it has become recognized as a major factor in enhancing tolerance to abiotic stresses. Though various mechanisms have already been explored for MT action, in this review, we have focused on the role of MT in modulating sugar metabolism, sensing, and their transporters to improve stress adaptation. MT regulates sucrose mobilization via sucrose synthase and invertase activities, upregulates hexose transporters (STP, sugar transportor family), SWEET (sugars will eventually be exported transporters) and SUT (sucrose transporters) for efficient carbohydrate allocation and integration with SnRK1/ABA (sucrose non-frmenting 1-related kinase/Abscisic acid) pathways to sustain photosynthesis, and prime reactive oxyggen species (ROS) scavenging. Sugar signaling through sugar transporters enables efficient sugar allocation and accumulation, serving as osmoprotectants, enhancing antioxidant defenses, and modulating stress-responsive gene expression. Future omics-driven dissection of MT-sugar networks, coupled with CRISPR validation and field applications, promises resilient crop varieties for saline and arid environments.