Regulation of Rice Grain Weight by Fatty Acid Composition:\nUnveiling the Mechanistic Roles of <i>OsLIN6</i> by OsARF12

Fatty\nacids play a putative role as second messengers of phytohormones\nand regulate the rice grain weight. However, the inner mechanism is\nstill unclear and needs to be further studied. In this study, we identified\nthat oleic acid (C18:1) negatively correlates while linoleic acid\n(C18:2) positively correlates with rice grain weight. Field trials\nshowed that 1000-grain weight was significantly reduced when treated\nwith the fatty acid synthesis inhibitor, Firsocostat S enantiomer\n(FSE), at the heading and flowering stages. RNA-seq analysis revealed\nthat FSE affects grain weight by modulating processes, such as glycolysis,\nsucrose metabolism, and hormone signaling. Notably, FSE inhibited\nthe expression of <i>OsLIN6</i>, which is responsible for\ntransporting C18:1 to the phosphatidylcholine pool for C18:2 synthesis.\nCompared with the wild type (WT), the <i>OsLIN6</i> knockout\nmutant exhibited a lower grain weight, an increased C18:1 content,\nand a decreased C18:2 content. Importantly, OsARF12 was shown to bind\nto the <i>OsLIN6</i> promoter and activate its expression.\nIn summary, this study highlights the crucial role of the fatty acid\nsynthesis gene, <i>OsLIN6</i>, which was regulated by OsARF12,\nin rice grain weight determination, thus establishing the molecular\nlink between fatty acid synthesis and auxin signaling.