14001:

Wall-associated kinases (WAKs): signalling between the wall and the cytoplasm.

Authors:	Wagner, Tanya, A.(A)Anderson, Cathy(A)Kohorn, Bruce, D.(A)
Affiliations:	(A): Duke University DCMB Group
Presenter:	Wagner, Tanya A., tawagner@duke.edu

The plant cell wall is a dynamic structure, providing strength, but also changing to allow cell growth and to respond to external stimuli. Until now, no molecule in plants has been identified that bridges the wall to the cytoplasm. A family of five Waks (Wall-associated kinases) has been isolated from Arabidopsis. They have an extracellular domain that is tightly linked to the cell wall, a single transmembrane domain, and a cytoplasmic serine/threonine kinase. Wak antisense expression is lethal indicating that Waks are essential. Family members diverge in their extracellular domain, and thus may be functionally distinct. Waks are differentially expressed in plant organs, although there is significant overlap of expression. We used transcriptional GUS fusions to examine the cell-type expression of Wak2. Wak2 is expressed in a developmental pattern at junctions of organs, the root apical meristem, and the cotyledon margin. Thus, Wak2 expression correlates with tissues or cells undergoing compression. Wak2 expression is also induced by wounding and INA treatment. The extracellular domain of Wak2 interacts with an o-methyl transferase and a seed imbibition protein in the yeast two-hybrid screen. This is consistent with the predicted role of Waks in wall signalling, since seed imbibition requires cell expansion and o-methyl transferases are involved in lignin biosynthesis.