Takayuki Kohchi: Genetic mechanisms of sex determination and sexual differentiation in Marchantia polymorpha

Land plants exhibit alternation of generations. The gametophyte generation include the processes of sex differentiation that give rise to gametes, such as egg and sperm cells. The liverwort Marchantia polymorpha is a dioicous model organism suitable for analyzing the mechanisms underlying sex differentiation in the gametophytic generation. However, the molecular basis of plant germline development remains largely unknown. Previously, we identified that BONOBOs (BNBs), members of the basic helix-loop-helix (bHLH) transcription factors, as key regulators of germline cell differentiation in land plants. Here, we report the establishment of a trans-activating system that directly reprograms M. polymorpha somatic cells into germline cells through ectopic overexpression of MpBNB from its endogenous locus using an inducible CRISPR activation system. The resulting germline cells exhibited developmental patterns similar to those of the wild-type cells. Time-course RNA-seq analysis revealed that this system recapitulates germline developmental processes in M. polymorpha at a transcriptional level. Furthermore, we performed single-nucleus RNA-seq (snRNA-seq) using this system to understand the process at the cellular level. In this seminar, I would also like to discuss the genetic network involved in sex determination and sexual differentiation, as revealed by our recent findings.