The miR1866– OsUBP7 regulatory module promotes grain yield and seed dormancy through abscisic acid signaling in rice

Higher grain weight and stronger seed dormancy are key objectives for improving rice (Oryza sativa) yield and inhibiting pre-harvest sprouting. Therefore, identifying genes that coordinately regulate grain weight and seed dormancy is an urgent priority. Here, we report that knocking out miR1866 (KO1866) increased grain weight and reinforced dormancy. We identified the transcript of ubiquitin-specific processing protease 7 (OsUBP7), which encodes a protein with deubiquitination activity in vitro, as the primary target of miR1866. Consistent with miRNA-directed repression, OsUBP7 transcript abundance generally showed a spatiotemporal pattern opposite to miR1866 accumulation during rice development. Overexpression of native OsUBP7 (UBP7-OE) or a miR1866-resistant form (mUBP7-OE) phenocopied KO1866 by producing heavier grains with stronger dormancy. The miR1866-OsUBP7 module also altered the expression of genes associated with sucrose and starch metabolism, cell-cycle control, grain development, and abscisic acid (ABA) biosynthesis and signaling. Accordingly, KO1866, UBP7-OE, and mUBP7-OE plants contained more ABA and responded more sensitively to exogenous ABA than wild type. OsUBP7 interacted with OsDA1 (encoded by Os06g0182500) and UBIQUITIN-CONJUGATING ENZYME (OsUCE1; encoded by Os02g0833300), thereby affecting hull cell division and ABA signaling and ultimately regulating grain weight and seed dormancy, respectively. Our results indicate that the miR1866-OsUBP7 module regulates grain weight and seed dormancy in rice, highlighting its potential for engineering crops with improved yields and stronger seed dormancy.