We recently reported that production of reactive oxygen species (ROS) is essential for auxin-induced gravitropic signaling. Here, we investigated the role of phosphatidylinositol 3-kinase and its product, PtdIns(3)P, in auxin-mediated ROS production and the root gravitropic response. Pretreatment with LY294002, an inhibitor of PtdIns 3-kinase activity, blocked auxin-mediated ROS generation, and reduced the sensitivity of root tissue to gravistimulation. The amount of PtdIns(3)P increased in response to auxin, and this effect was abolished by pretreatment with LY294002. In addition, sequestration of PtdIns(3)P by transient expression of the endosome binding domain in protoplasts abrogated IAA-induced ROS accumulation. These results indicate that activation of PtdIns 3-kinase and its product PtdIns(3)P are required for auxin-induced production of ROS and root gravitropism.
Bibliographical noteFunding Information:
We thank Drs. Bin Goo Kang, Jong Sub Lee, Yang Do Choi, Chris Wolverton and Michael Evans for helpful discussions and encouragement during the course of this research. We also gratefully acknowledge Dr. Nina Fedoroff for critical reading of the manuscript. This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the Center for Cell Signaling Research at Ewha Womans University and Crop Functional Genomics Center (Grant CG133 to Y.S.B.), and by a grant from KOSEF to the Environmental Biotechnology Research Center (Grant R15-2003-012-01003-0 to K.H.N). K.H.N was a recipient of a grant from the Brain Pool (031-1-17) of the Korean Federation of Science and Technology Societies, and J.H.J. was the recipient of a BK21 postdoctoral fellowship.
- Arabidopsis thaliana
- Phosphatidylinositol 3-kinase
- Reactive oxygen species