Specific combinatorial mutations in MIR396 genes enlarge the grain size and modulate the plant architecture in rice

miR396 is a key growth regulator in plants, however, the molecular mechanisms underlying its functions remained to be revealed. Here, through systematically gene-editing, we found that among the MIR396 family genes, MIR396e and -f were the main regulators of rice growth. mir396ef mutations could increase the grain yield through significantly enlarging the grain size. In addition, mir396ef mutations promoted the seedling growth and modulated the plant architecture by promoting the elongations of leaves (including leaf blades and sheaths) and panicles but suppressing the elongation of internodes, especially the uppermost internode. Our research reveals that mir396ef mutations promote the growth and organ elongation by significantly increasing the level of the gibberellin (GA) precursor, mevalonic acid (MVA), which subsequently activates the GA pathway. Our results also indicate that miR396 regulates the internode elongation through a different mechanism (probably through controlling SD37 expression) from the GA pathway. These results reveal two pathways by which miR396 regulates rice growth and provide valuable gene-editing targets to increase rice productivity. RNA-seq using the seedling shoots, developing uppermost internodes and young panicles (0.6–0.8 mm) of the wild type and mir396ef mutations. Two independent lines of mir396ef were used in the the transcriptome analyses of the seedling shoots. There are three biological replicates