Abstract
Stomata in the epidermis regulate gas exchange between plants and atmosphere. Stomatal opening, which is mediated by blue-light receptor phototropins, is driven by activation of the plasma membrane H+-ATPase. Under drought stress, a phytohormone abscisic acid (ABA) induces stomatal closure to prevent water loss from plants. To understand signaling mechanisms of stomatal opening and closure, we performed mutant screening focused on stomatal aperture-dependent transpiration in detached leaves from EMS-treated Arabidopsis thaliana and isolated rtl (rapid transpiration in detached leaves) mutants. Of these, rtl1 showed open-stomata, dwarf and pale green phenotypes. In addition, ABA-dependent inhibition of light-induced stomatal opening and ABA-induced stomatal closure were impaired in this mutant. However, rtl1 showed normal ABA sensitivities in seed germination and root elongation, suggesting that ABA-insensitive phenotype is only observed in stomatal guard cells of rtl1. We are trying to identify RTL1 locus by map-based cloning and will discuss these results.
