title: Changes in Ca2+ metabolism in Arabidopsis guard cells in response to blue light.
abstract: Phototropins are blue light receptors that mediate responses such as phototropism, chloroplast movement, stomatal opening and leaf expansion. One candidate signaling molecule from phototropins is cytosolic Ca(2+), since phototropins increase the cytosolic Ca(2+) in seedlings and mesophyll cells. The potential involvement of Ca(2+) in the blue light-dependent activation of plasma membrane H(+)-ATPase in guard cells has been reported, but it is not yet known whether cytosolic Ca(2+) in guard cells increases in response to blue light. We recently studied changes in the cytosolic Ca(2+) in guard cells in response to blue light using aequorin-transformed Arabidopsis. We detected no increase in Ca(2+) prior to blue light-dependent activation of plasma membrane H(+)-ATPase that depended on phototropins. But we detected a photosynthesis-dependent Ca(2+) increase. Only when the external K(+) concentration was low did blue light induce Ca(2+) influx based on phototropin-mediated membrane hyperpolarization. In this addendum, I discuss Ca(2+) changes in response to blue light in guard cells and phototropin-mediated Ca(2+) signaling.
authors.affiliation: Department of Biology, Osaka Medical College, Takatsuki, Japan. bio006@art.osaka-med.ac.jp
authors.forename: Akiko
authors.initials: A
authors.lastname: Harada