Regulation of Grain Chalkiness and Starch Metabolism by FLO2 Interaction Factor 3, a bHLH Transcription Factor in Oryza sativa

Chalkiness is a key determinant that directly affects the appearance and cooking quality of rice grains. Previously, Floury endosperm 2 (FLO2) was reported to be involved in formation chalkiness; however, its regulation mechanism still unclear. Here, FLO2 interaction factor 3 (OsFIF3), bHLH transcription factor, identified analyzed Oryza sativa. A significant increase chalkiness observed OsFIF3-overexpressed grains, coupled with round, hollow filling starch granules reduced grain weight. OsFIF3 evolutionarily conserved monocotyledons, but variable dicotyledons. Subcellular localization revealed predominant nucleus. The DAP-seq (DNA affinity purification sequencing) results showed could affect transcriptional accumulation β-amylase 1, α-amylase isozyme 2A-like, pectinesterase 11, β-glucosidase 28 like, pectinesterase, sucrose transport protein 1 (SUT1), through binding CACGTG motif on their promoters. Moreover, SUT1 abundant signals expression reduction overexpression lines, further confirming OsFIF3’s role metabolism energy material allocation. Taken together, these findings show inhibits SUT1, thereby increasing affecting