Abstract
Manipulating grain size demonstrates great potential for yield promotion in cereals since it is tightly associated with grain weight. Genetically, grain size is under complicated molecular and genetic modulation of different signaling and metabolic pathways. Several pathways modulating grain size have been elaborated in rice, but the possible crosstalk between the ingredients are rarely studied, together with the underlying mechanism. OsmiR396 negatively regulates grain size through targeting OsGRF4 and OsGRF8, and proves to be multi-functioning. G proteins function extensively in rice to regulate grain size. Here we showed that expression of GS3 gene that encodes Gγ-protein was down-regulated in the young embryos of MIM396, GRF8OE and GS2OE plants. Multiple biochemical assays proved possible transcriptional regulation of GRF4 and GRF8 on GS3 gene. Further genetic relation analysis revealed tight genetic association between not only OsmiR396 and GS3 gene, but also GS2 and GS3 gene. Thus, we revealed that the miR396 pathway and the G protein pathway could cross talk in the regulation of grain size.