Role of the R2R3-MYB Transcription Factor SHOT GLASS in Promoting Gemma Cup Development and Gametangiophore Formation in the Liverwort Marchantia polymorpha

This study explores the role of the R2R3-MYB transcription factor, SHOT GLASS (MpSTG), in the liverwort Marchantia polymorpha. MpSTG is identified as a crucial regulator of gemma cup development and is predominantly expressed in gemma cups, apical notches, and sexual reproductive organs. Loss-of-function mutants in MpSTG form abnormal structures lacking gemmae and fail to develop sexual reproductive organs. To identify factors downstream of MpSTG that regulate gemma cup development, transcriptomic changes in 1-week gemmalings of MpSTG-GR plants were analyzed using RNA sequencing. Differential gene expression analysis revealed that MpSTG overexpression induced by 2- and 8-hour DEX treatments upregulated 82 and 297 genes, respectively, while downregulating 36 and 164 genes. These findings suggest that MpSTG is a key transcription factor regulating both vegetative and sexual reproduction in M. polymorpha.