OsLUGL involved in floral development through regulating auxin level and OsARFs expression in rice (Oryza sative L.)

Specification of floral organ identity is critical for floral morphology and inflorescence architecture. Floral organ identity in plants is controlled by floral homeotic A/B/C/D/E-class genes. Although multiple genes regulate floral organogenesis our understanding of the regulatory network remains fragmentary. Here, we characterized rice floral organ gene KAIKOUXIAO (KKX), mutation of which produces an uncharacteristic open hull, abnormal seed, and semi-sterility. KKX encodes a putative LEUNIG-like (LUGL) transcriptional co-repressor. OsLUGL is preferentially expressed in young panicles and its protein can interact with OsSEU, which functions were reported as an adaptor for LEUNIG. OsLUGL-OsSEU functions together as a transcriptional regulatory complex to control organ identity specification through regulation of MADS-box genes. During this process, SEP3 (such as OsMADS8) and AP1 (such as OsMADS18) serve as the DNA-binding partner of OsLUGL-OsSEU complex. Further studies indicated that OsMADS8 and OsMADS18 could bind the promoter of OsGH3-8 and regulate its expression. The altered expression of OsGH3-8 caused the increased auxin level and the decreased expression of OsARFs. Overall, our results demonstrate a possible pathway whereby OsLUGL-OsSEU-OsAP1-OsSEP3 complex as a transcriptional regulator by targeting the promoter of OsGH3-8 directly, affecting auxin level, OsARFs expression level and thereby influencing floral development. These findings provide a valuable insight into the molecular functions of OsLUGL in rice floral development. HighlightOsLUGL through forming OsLUGL-OsSEU-OsAP1-OsSEP3 complex regulate OsGH3-8 expression, and regulate auxin level and OsARFs expression indirectly. This work is a new insight to floral development molecular mechanism.