Insights into the Metabolism of Rice Leaves (Oryza sativa L.) under Shade Stress by Investigating the Metabolite Profile Using Gas Chromatography-Mass Spectrometry (GC-MS) Analysis

Plant metabolites possess noteworthy biological activities, and their biosynthesis can be influenced by fluctuating light conditions. To elucidate the underlying molecular mechanisms and signaling pathways in rice plants subjected to shade stress, the study investigated the impact of shade on total polyphenols, total chlorophyll, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, and metabolite composition in rice leaves using gas chromatography-mass spectrometry (GC-MS). Our results revealed a substantial impact of shading on rice plants as there were reductions in both polyphenol and chlorophyll contents. Additionally, the DPPH radical scavenging activity was found to be diminished under shade conditions. Through GC-MS profiling of rice leaves, it was observed that under no-shade conditions, the plant exhibited an accumulation of abundant monoterpenes, phytosterols, and isoprenoids. Noteworthy compounds included bicyclo[3.1.1]heptane, 2,6,6-trimethyl-, [1S-(1).alpha), 2 isomer (30.89%), 3-Octene, (E)- (22.58%), phytol (8.16%), stigmasterol (7.98%), 22,23-dihydro-stigmasterol (6.06%), 5-Cholesten-3-ol, 24-methyl- (5.22%), and vitamin E (4.67%). In contrast, under shade conditions, rice leaves exhibited an accumulation of fatty acid esters, with notable compounds including 3-Octene, (Z)- (29.14%), ethyl ester of hexadecanoic acid (14.52%), ethyl ester of dodecanoic acid (8.33%), ethyl ester of octadecanoic acid (8.07%), squalene (6.63%), and methyl ester of 9-Octadecenoic (Z)- (6.23%). By examining the composition of metabolites, our findings unraveled the underlying molecular processes and signaling pathways involved in rice leaf metabolism under conditions of reduced light exposure and may have implications for further research on the potential health benefits and utilization of these compounds in diverse applications.