Walker, Robin K. , Ma, Wei , Leng, Qiang , Berkowitz, Gerald .
Pathogen perception signaling cascades in the guard cell: involvement of Ca-conducting CNGC channels, calmodulin, nitric oxide, and hydrogen peroxide.
Work from this lab has identified cyclic nucleotide gated channel (CNGC) mediated Ca influx into the cytosol, resulting rise in Ca/calmodulin (CaM), and Ca/CaM-activated nitric oxide (NO) generation as steps in a plant innate immunity signaling cascade responding to the bacterial pathogen associated molecular pattern (PAMP) elicitor lipopolysaccharide (LPS). This signaling pathway leads to the hypersensitive response (HR) to avirulent pathogens in planta. Melotto et al. (2006, Cell) have shown that NO in the guard cell is a component of a PAMP responsive pathway in the guard cell that leads to stomatal closure and shares some components of the signaling cascade responding to ABA. Since ABA signaling involves NO as well as H2O2 generation, here we investigate whether CNGCs, CaM, and NO production in the guard cell (studied in epidermal peels) are involved with H2O2 generation. We find that LPS application leads to H2O2 generation. An inhibitor of cAMP production, a CaM antagonist, and an inhibitor of arginine-dependent NO production all block H2O2 generation. A similar block occurs in a cngc2 Arabidopsis mutant. We also find that inward cation currents in oocytes injected with CNGC2 mRNA (and not in water-injected controls) are activated by H2O2 Melotto et al. found that salicylic acid (SA) production is involved in PAMP-responsive stomatal closure signaling. cngc2 mutant plants lack HR; this phenotype can be complemented by application of an NO donor. The mutant also has constitutively high PR1 expression and PR1-dependent SA production. The NO donor reduces PR1 expression in cngc2 mutants. These results identify the CNGC-dependent signaling pathway as leading to, as well as responding to H2O2 generation in the guard cell. Supported by NSF award 0344141.
Log in to add this item to your schedule
1 - University of Connecticut, Department of Plant Science, Agricultural Biotechnology Laboratory, 1390 Storrs Rd., U-4163, Storrs, CT, 06269, U.S.A.
2 - Yale University, Department of Cellular and Molecular Physiology
ROS, Ca, cAMP, Ion channel, Hypersensitive response.
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM