G1-mediated OsMADS1 repression regulates sterile lemma development in rice.

Key message: This study shows that transcription factor G1 represses the floral development regulator OsMADS1 by binding to the CArG-box and YACTGTW motifs in OsMADS1 promoter to specify sterile lemma development in rice. In addition, we first demonstrate that G1 physically interacted with the OsMADS1 K-box domain, which enhances G1-mediated repression of OsMADS1. Sterile lemma is a unique organ formation during the development of rice spikelet, and the regulatory mechanism underlying its development remains poorly understood. Previous studies showed that transcription factor G1 (Os07g0139300) plays a critical role in sterile lemma development. Here, we further reveal that G1 transcriptionally represses the expression of OsMADS1, a key gene regulating floral organ development in rice, by directly binding to the CArG box and YACTGTW motifs in its promoter. Importantly, we first demonstrate that G1 specifically targets the K-box domain of OsMADS1 to establish physical interaction, and the interaction significantly enhances G1-mediated transcriptional repression of OsMADS1 expression. The feedback regulatory loop formed between G1 and OsMADS1 provides a key clue for further elucidating the molecular mechanisms underlying sterile lemma development.