Post Doctoral Researcher University of California San Diego San Diego, California
Body of Abstract: Due to the rising atmospheric CO2 concentration, CO2 control of stomatal conductance and water loss of plants will have profound effects on global plant water loss, water use efficiency, leaf heat stress and optimal stomatal conductance of plants, including crops. Elevated CO2 concentrations in leaves cause stomatal closure, whereas reduced CO2 concentrations result in stomatal opening. However, the molecular signal transduction mechanisms that mediate CO2-controlled stomatal movements and the primary CO2 sensor remain incompletely known. We found that high CO2 induces interaction of the MAP kinase MPK12 with the HT1 protein kinase that is mainly expressed in guard cells (Takahashi et al 2022 Science Adv.). At low CO2, MPK4 and MPK12 do not interact with HT1 kinase enabling HT1 activation. Activated HT1 phosphorylates a Raf-like protein kinases CONVERGENCE OF BLUE LIGHT AND CO2 (CBC1) resulting in stomatal opening. HT1 and MPK12 mutants reduce the CO2 induced MPK12-HT1 interaction and maintains HT1 kinase activity (Takahashi et al 2022 Science Adv.). We have successfully identified the upstream regulators of the CBC1 kinase but the downstream regulators of CBC1 are yet to be identified. Approaches that are identifying downstream targets of CBC1 provide new insights into the CO2 signaling pathway. New insights into the stomatal CO2 signaling pathway will be presented.