Abstract
The evolution of special types of cells requires the acquisition of new gene regulatory networks controlled by transcription factors (TFs). In stomatous plants, the stomatal formation is regulated by a TF module formed by subfamilies Ia and IIIb basic helix-loop-helix TFs (Ia-IIIb bHLH); however, how this module evolved during land plant diversification remains obscure. Here, we show that, in the astomatous liverwort Marchantia polymorpha, a Ia-IIIb bHLH module regulates the development of a unique sporophyte tissue, the setae, which are found in mosses and liverworts. The sole Ia bHLH gene, MpSETA, and a IIIb bHLH gene, MpICE2, regulate cell division and/or differentiation of seta lineage cells. MpSETA can partially replace the stomatal function of Ia bHLH TFs in Arabidopsis thaliana, suggesting the common regulatory mechanism underlying setal and stomatal formation. Our findings reveal the co-option of a Ia-IIIb bHLH TF module for regulating the cell fate determination and/or cell division of distinct types of cells during the evolution of land plant.
Competing Interest Statement
The authors have declared no competing interest.
