Initiation of asexual reproduction by the AP2/ERF gene GEMMIFER in Marchantia polymorpha

Plants can propagate their own clones through asexual reproduction. Genetic and hormonal factors regulating asexual reproduction have begun to be elucidated in the liverwort Marchantia polymorpha, which produces asexual propagules called gemmae within the gemma cups. Here, we report an APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) family gene, GEMMIFER (MpGMFR), as a key regulator of asexual reproduction in M. polymorpha. Suppression of MpGMFR function using genome editing and artificial microRNA (amiRNA) results in the loss of gemma and gemma cup formation. In contrast, activation of MpGMFR function using a dexamethasone-inducible system promotes gemma and/or gemma cup formation, depending on the induction conditions. Notably, transient activation of MpGMFR induces gemma initial cells at the meristem, which develop into mature gemmae that are capable of reproducing as new individuals after detachment. MpGMFR expression was detected from the meristem through to the early stages of gemma development including gemma cup floor cells, which precedes the expression of GEMMA CUP-ASSOCIATED MYB1 (MpGCAM1) in the early gemma development. Expression of MpGCAM1 was promoted by MpGMFR, and overexpression of MpGCAM1 partially restored gemma and gemma cup formation in the Mpgmfr mutant. Taken together, MpGMFR acts as a master regulator for the initiation of gemma and gemma cup development by activating MpGCAM1 as a key downstream effector. We anticipate this finding to serve as a foundation for studying the evolution of extra meristem formation in plant bodies, which may have made a significant contribution to the prosperity of plants on land.