Present address: Department of Biological Sciences, University of Alaska-Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA.
ARL2, ARG1 and PIN3 define a gravity signal transduction pathway in root statocytes
Article first published online: 23 OCT 2007
The Plant Journal
Volume 53, Issue 2, pages 380–392, January 2008
How to Cite
Harrison, B. R. and Masson, P. H. (2008), ARL2, ARG1 and PIN3 define a gravity signal transduction pathway in root statocytes. The Plant Journal, 53: 380–392. doi: 10.1111/j.1365-313X.2007.03351.x
- Issue published online: 23 OCT 2007
- Article first published online: 23 OCT 2007
- Received 20 July 2007; revised 28 September 2007; accepted 16 October 2007.
- signal transduction;
ALTERED RESPONSE TO GRAVITY1 (ARG1) and its paralog ARG1-LIKE2 (ARL2) are J-domain proteins that are required for normal root and hypocotyl gravitropism. In this paper, we show that both ARL2 and ARG1 function in a gravity signal transduction pathway with PIN3, an auxin efflux facilitator that is expressed in the statocytes. In gravi-stimulated roots, PIN3 relocalizes to the lower side of statocytes, a process that is thought to, in part, drive the asymmetrical redistribution of auxin toward the lower flank of the root. We show that ARL2 and ARG1 are required for PIN3 relocalization and asymmetrical distribution of auxin upon gravi-stimulation. ARL2 is expressed specifically in the root statocytes, where it localizes to the plasma membrane. Upon ectopic expression, ARL2 is also found at the cell plate of dividing cells during cytokinesis, an area of intense membrane dynamics. Mutations in ARL2 and ARG1 also result in auxin-related expansion of the root cap columella, consistent with a role for ARL2 and ARG1 in regulating auxin flux through the root tip. Together these data suggest that ARL2 and ARG1 functionally link gravity sensation in the statocytes to auxin redistribution through the root cap.