UC San Diego

Stomata are structures on the epidermis of leaves in plants that regulate exchange of gasses with the surrounding environment during photosynthesis and evapotranspiration. Because evapotranspiration serves to cool leaves, stomata also regulate canopy leaf temperatures. In grasses, stomata are made up of a central pore flanked by two guard cells and two subsidiary cells that help to regulate stomatal pore aperture. Subsidiary cells are hypothesized to promote more efficient responses to factors impacting stomatal aperture including atmospheric CO2 levels and drought. To date, CO2 signaling has not been investigated in grasses and more upstream transducers of the CO2 mechanism remain to be identified. Using infrared thermography, a mutagenized population of Brachypodium distachyon was screened for potential defects in stomatal responses.

The patterning of stomata also impacts overall gas exchange functionality in a plant. Stomatal development has been characterized in Arabidopsis thaliana and orthologues have been identified in members of the grass family including maize, rice, barley and Brachypodium distachyon. Transcription factors that are responsible for triggering changes in cell fate in the stomatal lineage are regulated by a kinase cascade that is initiated by accumulation and recognition of EPIDERMAL PATTERNING FACTORs (EPFs). EPFs have been shown to be processed and activated by members of the subtilase (SBT) family in Arabidopsis. The role of SBTs in stomatal development in Brachypodium has not been explored. Here, a reverse genetic screen for stomatal development in mutagenized Brachypodium distachyon lines endeavors to characterize the role of members of the SBT family in stomatal patterning.