Mobile MUTE specifies subsidiary cells to build physiologically improved grass stomata ($)

Plants breathe through pores called stomata on leaf surfaces. Stomata are the point of contact with the outside world as they allow gas exchange (e.g., CO₂ for photosynthesis) and transpiration. Grasses have evolved to form more efficient stomata in which the guard cells are flanked by additional subsidiary cells. Therefore, grasses form superior 4-celled stomata for efficient functioning; stomata can open wider or close faster in response to varying conditions. Starting with a loss-of-function mutant subsidiary cell identity defective (sid), Raissig et al. describe how in the model grass Brachypodium distachyon a transcription factor called MUTE physically moves from guards cells to adjacent cells to recruit them for formation of the 4-celled stomata complex. The corresponding MUTE protein from Arabidopsis does not move between cells and fails to rescue the loss-of-function sid mutant. (Summary by Nidhi Sharma) Science 10.1126/science.aal3254