Insight into CO₂ signal transduction mechanisms in Arabidopsis guard cells

Abstract

CO₂ is a physiological signal that regulates stomatal movements. High CO₂ concentrations reduce stomatal aperture, whereas low concentrations lead to stomatal opening. However, molecular mechanisms underlying stomatal CO₂ sensing and signaling are largely unknown. To identify genes that function in CO₂ responses in guard cells, we isolated CO₂ insensitive mutants (ht1-ht2 and cdi1-cdi10) through a high-throughput leaf thermal imaging. The isolated mutants are categorized into 3-groups according to their phenotypes; (1) impaired in stomatal opening under low CO₂ concentrations (2) impaired in stomatal closing under high CO₂ concentrations (3) impaired in both CO₂ responses. Characterization of these mutants has begun to yield insight into the mechanisms by which stomatal CO₂ response are controlled. We will discuss the current status of functional analysis of identified CO₂ regulators and future prospects.