Abstract
Secretory peptides EPF1 and EPF2 negatively regulate stomata developmental pathway. STOMAGEN positively regulates stomatal density. Disruption of genes for TMM, the ER-family receptor kinases, or MAPK cascade components results in excess formation of stomata without proper placement. The MAPK cascade targets the bHLH class transcription factor SPCH, which is required for entry into the stomatal lineage. Taken all genetic evidences in consideration, we can generate a model in which the extracellular signaling peptides EPF1 and EPF2 are perceived by putative receptor complexes that contain TMM and ER family protein, which in turn activates the MAPK cascade, phsphorylate SPCH, and inhibit stomatal formation. We are trying to reconstitute the whole components by transient expression in tobacco leaves, and verify the above model. Here we show that overexpression of EPF1 and EPF2 decreased SPCH-GFP protein level. STOMAGEN, on the other hand increased the SPCH-GFP protein. Our study also provided evidence that the action of EPF1and EPF2 on SPCH-GFP level depends on MAPK cascade. Our results support the above model.
