KANADI promotes thallus differentiation and FR-induced gametangiophore formation in the liverwort Marchantia

Abstract

In angiosperms, KANADI transcription factors have roles in the sporophyte generation regulating tissue polarity, organogenesis and shade avoidance responses, but are not required during the gametophyte generation. Whether these roles are conserved in the gametophyte-dominant bryophyte lineages is unknown, which we examined by characterising the sole KANADI ortholog, MpKAN, in the liverwort Marchantia polymorpha. In contrast to angiosperm orthologs, MpKAN functions in the gametophyte generation in Marchantia, where it regulates apical branching and tissue differentiation, but does not influence tissue polarity in either generation. MpKAN can partially rescue the sporophyte polarity defects of kanadi mutants in Arabidopsis, indicating that MpKAN has conserved biochemical activity to its angiosperm counterparts. Mpkan loss-of-function plants display defects in far-red (FR) light responses. Mpkan plants have reduced FR-induced growth tropisms, have a delayed transition to sexual reproduction and fail to correctly form gametangiophores. Our results indicate that MpKAN is a modulator of FR responses, which may reflect a conserved role for KANADI across land plants. Under FR, MpKAN negatively regulates MpDELLA expression, suggesting that MpKAN and MpDELLA act in a pathway regulating FR responses, placing MpKAN in a gene regulatory network exhibiting similarities with those of angiosperms.