Signal integration in stomatal development

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Stomata, which are a key evolutionary adaptation of land plants, are also a visually accessible model system for analyzing how plant development progresses from cell proliferation, fate commitment, and the control of cell size, position, and shape. Life requires gas exchange between shoots and the atmosphere. CO2 entry yields new carbohydrates in photosynthesis, and H2O evaporation cools the plant and the planet. These gases move through stomata, epidermal valves made up of two guard cells around a pore whose opening and closing allows CO2 influx and minimizes water loss. Despite their key role in global gas levels and agriculture, how stomata form is still in its discovery phase. Specific foci: (i) Cross-talk between young guard cells likely generates the mirror-like symmetry of the valve. Only the MUS gene is known shape this symmetry, whereas an entire gene pathway is likely involved, and how cellular events coordinate shaping is still obscure. (ii) We found stomatal patterning to be regulated by local levels of the master plant hormone auxin, but have yet to determine the extent to which all major auxin signaling pathways are involved. (iii) The FOUR LIPS (FLP) MYB protein ensures that stomata contain just two cells, but how the integrated action of many FLP target genes restrict proliferation and control auxin pathways needs to be determined. Key goals: (1) Define how receptor signaling by MUSTACHES coordinates cell biology with valve shaping, and identify additional members of the pathway. (2) Probe auxin control of stomatal development using fluorescence reporters (DII), chemical inhibitors, and mutants related to the auxin receptor and transcription factor pathways. (3) Analyze how FLP integrates the expression of key genes to orchestrate cell proliferation and patterning, blocks stomatal enlargement resulting from excess and abnormal DNA multiplication, and coordinates these events via auxin signaling.