LcASR enhances tolerance to abiotic stress in Leymus chinensis and Arabidopsis thaliana by improving photosynthetic performance

SUMMARY As a crucial forage grass, Leymus chinensis plays significant roles in soil and water conservation owing to its robust stress resistance. However, the underlying molecular mechanisms of its stress tolerance remain unclear. In this study, a novel gene, designated as LcASR (Abiotic Stress Resistance in Leymus chinensis), imparting resilience to both high light and drought, was identified. Under normal growth conditions, heterologous overexpression of LcASR in Arabidopsis (HO lines) showed no significant difference in appearance compared to wild‐type. Nevertheless, HO lines accumulate significantly higher chlorophyll content during the dark‐to‐light transition compared to the wild‐type, indicating that the LcASR protein participates in chlorophyll synthesis during chloroplast development. Meanwhile, transgenic Arabidopsis and L. chinensis plants exhibited resistance to abiotic stresses such as high light and drought. Photosystem complexes analysis revealed that LHCII proteins remained stable within their respective complexes during high light stress. We hypothesize that LcASR may play a role in fine tuning of chlorophyll synthesis to enable plant adaptation to diverse stress conditions. Moreover, overexpression of LcASR in L. chinensis led to agronomically valuable traits such as deeper green color, higher biomass accumulation, prolonged withering period, and extended grazing durations. This study uncovers a novel gene in L. chinensis that enhances forage yield and provides valuable genetic resources for sheepgrass breeding. Significance Statement Using the recently developed genetic transformation system on Leymus chinensis and biochemical analysis, our research demonstrates that LcASR plays a role in fine‐tuning chlorophyll content, thereby enhancing the stability of the binding of LHCII to photosystem complexes under stress conditions. This finding highlights the potential of LcASR as a candidate gene for L. chinensis breeding.