A cis-acting bidirectional transcription switch controls sexual dimorphism in the liverwort.

Keiji Nakajima,Keitaro Okahashi,Tetsuya Hisanaga,Katsuyuki T Yamato,Ryuichi Nishihama,Masaki Shimamura,John L Bowman,Shohei Yamaoka,Takayuki Kohchi,Tomoaki Kajiwara

doi:10.15252/embj.2018100240

Abstract

Plant life cycles alternate between haploid gametophytes and diploid sporophytes. While regulatory factors determining male and female sexual morphologies have been identified for sporophytic reproductive organs, such as stamens and pistils of angiosperms, those regulating sex‐specific traits in the haploid gametophytes that produce male and female gametes and hence are central to plant sexual reproduction are poorly understood. Here, we identified a MYB‐type transcription factor, MpFGMYB, as a key regulator of female sexual differentiation in the haploid‐dominant dioicous liverwort, Marchantia polymorpha. MpFGMYB is specifically expressed in females and its loss resulted in female‐to‐male sex conversion. Strikingly, MpFGMYB expression is suppressed in males by a cis‐acting antisense gene SUF at the same locus, and loss‐of‐function suf mutations resulted in male‐to‐female sex conversion. Thus, the bidirectional transcription module at the MpFGMYB/SUF locus acts as a toggle between female and male sexual differentiation in M. polymorpha gametophytes. Arabidopsis thaliana MpFGMYB orthologs are known to be expressed in embryo sacs and promote their development. Thus, phylogenetically related MYB transcription factors regulate female gametophyte development across land plants.

Highlights

Plant life cycles alternate between haploid gametophytes and diploid sporophytes
While regulatory factors determining male and female sexual morphologies have been identified for sporophytic reproductive organs, such as stamens and pistils of angiosperms, those regulating sex-specific traits in the haploid gametophytes that produce male and female gametes and are central to plant sexual reproduction are poorly understood
Mapoly0001s0061 FEMALE GAMETOPHYTE MYB (MpFGMYB) is expressed in females and its loss resulted in female-to-male sex conversion

Summary

Introduction

While regulatory factors determining male and female sexual morphologies have been identified for sporophytic reproductive organs, such as stamens and pistils of angiosperms, those regulating sex-specific traits in the haploid gametophytes that produce male and female gametes and are central to plant sexual reproduction are poorly understood. We identified a MYB-type transcription factor, MpFGMYB, as a key regulator of female sexual differentiation in the haploid-dominant dioicous liverwort, Marchantia polymorpha. MpFGMYB is expressed in females and its loss resulted in female-to-male sex conversion. MpFGMYB expression is suppressed in males by a cis-acting antisense gene. SUF at the same locus, and loss-of-function suf mutations resulted in male-to-female sex conversion. The bidirectional transcription module at the MpFGMYB/SUF locus acts as a toggle between female and male sexual differentiation in

Methods

Results

Conclusion