Professor AOYAMA, Takashi (left)
Assistant Professor TSUGE, Tomohiko (center)
TANIGUCHI, Yukimi Y (right)

Phospholipids are major components of the eukaryotic cell membrane and act as signaling molecules for various intracellular events. We found the involvement of Arabidopsis thaliana phospholipase Dζ2 (PLDζ2)in root hydrotropism. The promoter activity of the PLDζ2 gene was localized to epidermal cells in the distal root elongation zone and lateral root cap cells adjacent to them, and that exogenous ABA enhanced the activity and extended its area to the entire root cap. In root hydrotropism experiments, pldζ2 mutations significantly retarded root hydrotropic responses. A drought condition similar to that used in a hydrotropism experiment enhanced the PLDζ2 promoter activity in the root cap, as did exogenous ABA. These results suggest that PLDζ2 responds to drought through ABA signaling in the root cap and accelerates root hydrotropism. This PLDζ2 function, as a signal transducer of drought stress, is presumably critical for plant survival in natural fields, where water deficiency is frequently a fatal problem for plants.