A RopGEF regulates asexual reproduction in the liverwort Marchantia polymorpha

Complex developmental programs regulate tissue and organ formation throughout the green plant lineage, from early diverging non-vascular lineages (bryophytes) to vascular flowering (angiosperm) plants. In the model liverwort Marchantia polymorpha, epidermal patterning gives rise to surface structures such as air pore complexes and gemma cups that house asexually-derived clonal liverwort propagules (gemmae), yet the underlying mechanisms regulating their development remain relatively obscure. In a new bioRxiv pre-print, Hiwatashi et al. (2018) describe the identification of the karappo mutant (meaning “empty”) which develops gemmae cups largely devoid of gemmae. The KARAPPO locus was found to encode a Rop guanine nucleotide exchange factor (GEF) that displays activity on the sole Marchantia Rop GTPase, MpROP. This work identifies KARAPPO/MpRop as a key regulator of the initiation of clonal regeneration in liverworts and provides a framework to assess the conservation of Rop signalling for key asymmetric cell division events in land plants. (Summary by Phil Carella) bioRxiv