Role of phenylpropanoid pathway in genetic regulation and physiological adaptation in arsenic stressed rice genotypes

This study investigates the role of the phenylpropanoid pathway in arsenic (As) contaminated rice genotypes under natural conditions, exploring the intricate relationship between genetic regulation and physiological adaptation. Differential approaches adapted by rice genotypes to counteract As exposure are elucidated here through analysis of enzyme activities and related gene expression patterns, docking simulations, and nutrient dynamics. Enzymatic analysis from the phenylpropanoid pathway revealed significant variations across rice genotypes, with Mini mansoori exhibiting notably higher activity levels of key enzymes (PAL, C4H, 4CL, CHI, DFR and F3H) compared to Sampoorna and Pioneer. Additionally, the gene expression profiling unveiled differential responses, with Mini mansoori and Pioneer demonstrating higher expression of genes (OsPAL, OsCHS, OsCHI, OsF3H, OsF3'H, OsFLS, OsDFR, and OsLAR) associated with As resistance and tolerance, compared to Sampoorna. Enrichment analysis emphasized the involvement of cinnamic acid biosynthesis and related pathways. Molecular docking depicted certain proteins, such as Os4CL, OsFLS, OsDFR, and OsLAR susceptible to As binding, potentially affecting enzymatic activity. Ionomic analysis unveiled that Mini mansoori maintained higher levels of essential nutrients such as Na, Ca, P, Mn, Mg, and Zn in grains. However, this contrasted with Pioneer and Sampoorna, which experienced nutrient imbalance likely due to higher As accumulation. Chlorophyll fluorescence analysis depicted that Mini mansoori and Pioneer maintained better photosynthetic efficiency under As toxicity compared to Sampoorna. Moreover, network analysis highlights the critical role of Mg and Na interaction with essential phenolics and flavonoids, in combating the stress. Harnessing this understanding, targeted breeding effort could yield As-resistant rice varieties with enhanced nutrient and flavonoid contents, addressing both food safety and malnutrition in affected regions.