CHARACTERIZATION OF THE PATHOGEN-REGULATED ARABIDOPSIS BONZAI1/COPINE1 PROTEIN AND ITS ROLE IN CALCIUM SIGNALING
Open Access
- Author:
- Lee, Tzuu-fen
- Graduate Program:
- Integrative Biosciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 20, 2008
- Committee Members:
- Timothy W Mcnellis, Committee Chair/Co-Chair
Surinder Chopra, Committee Member
Seogchan Kang, Committee Member
Paula Mc Steen, Committee Member
Andrew George Stephenson, Committee Member - Keywords:
- BON1
CPN1
defense
calcium
copine - Abstract:
- The Arabidopsis BONZAI1/COPINE1 (BON1/CPN1) gene is a suppressor of defense responses controlled by the disease resistance gene homolog SNC1. The BON1/CPN1 null mutant cpn1-1 has a recessive, temperature- and humidity-dependent lesion mimic phenotype that includes enhanced disease resistance and activation of Pathogenesis Related (PR) gene expression. This study shows that calcium perturbation activated defense responses in the absence of BON1/CPN1. Leaf infiltration with the calcium ionophore A23187 triggered strong PR gene expression specifically in cpn1-1 mutant plants grown under permissive conditions while co-infiltration of the calcium chelator EGTA attenuated this effect. This suggests that BON1/CPN1 is required for normal responses to calcium fluxes. Using a polyclonal anti-BON1/CPN1 antibody, the accumulation of BON1/CPN1 protein was shown to be up-regulated by the activation of defense signaling responses controlled by two Resistance (R) genes, SNC1 and RPS2. Promoter deletion analysis identified a 280 bp portion of the BON1/CPN1 promoter required for pathogen- and A23187-induced GUS expression, which occurred in a punctate pattern in treated leaves. Finally, two BON1/CPN1 promoter T-DNA mutants over-accumulated BON1/CPN1 despite T-DNA inserted extremely close to the BON1/CPN1 transcriptional start site. Our study explains the conditional nature of the cpn1-1 phenotype. These results are consistent with BON1/CPN1 being a calcium- and pathogen-responsive plant defense suppressor protein.