Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 4/4/2006
Publication Date: 5/17/2006
Citation: Cheng, N-H., Liu, J-Z., Brock, A., Nelson, R.S., Hirschi, K.D. 2006. Ca(2+) signaling and redox regulation: Roles of an Arabidopsis Glutaredoxin [abstract]. The 2nd Pan American Plant Membrane Biology Workshop. Membranes and Environmental Stresses I, May 17-20, 2006, South Padre Island, Texas. 24, p. 30. Interpretive Summary:
Technical Abstract: Redox states in all biological systems including plants are thought to play vital roles in maintaining and/or regulating cellular processes and metabolisms in response to extreme conditions, such as oxidative stresses, nutritional perturbation, and metabolic disorders. There is a growing body of evidence that Glutaredoxins (Grxs), along with glutathione and GSH reductase, may play critical roles in regulating the thiol group of proteins. Recently, PICOT-HD containing proteins (protein kinase C interacting cousin of thioredoxin homology domain) were identified as monothiol Grxs that are conserved in both prokaryotes and eukaryotes. The first plant PICOT-HD containing protein, CXIP1, was identified in a yeast functional screening, in which CXIP1 was able to activate the autoinhibited CAX1 and modulate Ca(2+)/H(+) antiport activity. Based on bioinformatic and functional analyses, CXIP1 is renamed as AtGRXcp. We further demonstrate that AtGRXcp is a chloroplast-localized monothiol Grx. In yeast expression assays, AtGRXcp localized to the mitochondria and partially suppressed the sensitivity of yeast cells to HO and protein oxidation. "In planta, AtGRXcp" expression was high in young cotyledons, green tissues and vascular bundles. Analysis of "AtGRXcp" null alleles demonstrated defects in early seedling growth under oxidative stresses. In addition, "atgrxcp" lines displayed increased protein carbonylation in chloroplasts. Thus, these findings suggest: 1) a conserved biological function among monothiol Grxs in protecting cells from protein oxidative damage; 2) AtGRXcp/CXIP1 may play a unique role in integrating redox signals with Ca(2+) signal transduction events in response to external stresses.