Session 2: Signal Transduction

Chair: Jeff Harper, Scripps Institute, La Jolla, USA

email: harper@scripps.edu


The session had three themes: Calcium signals, ion channels, and receptor kinases. The talks all emphasized combining biochemical and genetic approaches to make Arabidopsis more than just another small genome. The session was very "mooo..ving".

Janet Braam discussed progress on understanding the role of calcium binding proteins in the mechano-sensory response in Arabidopsis. One important direction being pursued is a biochemical understanding of the potential role of "touch induced" calcium binding proteins in modulating enzyme activities. Jeff Harper discussed how Calcium-Dependent Protein Kinases sense and respond to calcium signals. Evidence indicates that they are activated by a mechanism involving intramolecular binding of the calmodulin-like regulatory domain -- a model suggesting that CDPKs are fundamentally different from a typical calmodulin- dependent protein kinases. Zhen Ming Pei, who discovered a new chloride channel activated by CDPK phosphorylation, presented his most recent work on patch clamp analysis of ion channels in Arabidopsis guard cells. This technical achievement, in combination with the analysis of Arabidopsis mutants, promises to reveal important new insights into the electrophysiology of guard cell turgor regulation.
 

Six short poster talks followed.

Channels:

Bern Mueller-Roeber reported on a novel potassium channel that is regulated by calcium binding to EF-hand motifs present on the same polypeptide.

Bryan Lewis provided electrophysiological evidence that cold shock opens a calcium channel in the plasma membrane.

Rebecca Hirsch announced the first genetic disruption of a potassium channel in a higher plant and showed that this channel was important for potassium uptake by roots.
 

Receptor Kinases:

Zhen-Hui He presented evidence that a Wall Associated Kinase (WAK1) is essential for plant development and provides a potential signal transduction link between the cell wall and cytoplasm.

Eileen Maher reported on the use of dSpm transposon tagging to disrupt TMK, a receptor-like kinase with leucine rich repeats.

Julie Stone reported on progress toward identifying the phosphorylated sequence in RLK-5 (receptor-like kinase-5) which is recognized by KAPP (a type 2C protein phosphatase)