Neofunctionalisation of basic helix−loop−helix proteins occurred when embryophytes colonised the land

Clemence Bonnot, Alexander Hetherington, Clément Champion

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

ROOT HAIR DEFECTIVE SIX-LIKE (RSL) genes control the development of structures from single cells at the surface of embryophytes (land plants) such as rhizoids and root hairs. RSL proteins constitute a subclass (VIIIc) of the basic helix–loop–helix (bHLH) class VIII transcription factor family.

The Charophyceae form the only class of streptophyte algae with tissue-like structures and rhizoids. To determine if the function of RSL genes in the control of cell differentiation in embryophytes was inherited from a streptophyte algal ancestor, we identified the single class VIII bHLH gene from the charophyceaen alga Chara braunii (CbbHLHVIII).

CbbHLHVIII is sister to the RSL proteins; they constitute a monophyletic group. Expression of CbbHLHVIII does not compensate for loss of RSL functions in Marchantia polymorpha or Arabidopsis thaliana. In C. braunii CbbHLHVIII is expressed at sites of morphogenesis but not in rhizoids.

This finding indicates that C. braunii class VIII protein is functionally different from land plant RSL proteins. This result suggests that the function of RSL proteins in cell differentiation at the plant surface evolved by neofunctionalisation in the land plants lineage after its divergence from its last common ancestor with C. braunii, at or before the colonisation of the land by embryophytes.
Original languageEnglish
Pages (from-to)993-1008
Number of pages16
JournalNew Phytologist
Issue number2
Early online date4 Apr 2019
Publication statusPublished - 1 Jul 2019

Keywords / Materials (for Non-textual outputs)

  • basic helix−loop−helix (bHLH)
  • chara braunii
  • coleochate nitellarum
  • filamentous rooting cells
  • land plants
  • neofunctionalisation
  • root hair defective six like (RSL)
  • streptophyte algae


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