Physiological Functions and Biochemical Properties of Plant Cytochromes b561

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

Proposal: 0416742 ABSTRACT Ascorbate (vitamin C) has the ability to protect plants against the damaging affects of stress situations, such as drought, wounding, exposure to pollutants, high salt and pathogen attack. In addition, it is a cofactor to numerous metabolic enzymes and is involved in the biosynthesis of plant hormones. Therefore, ascorbate plays a key role in the control of plant growth and development, defense against pathogens and oxidative stress and in the regulation of cellular redox status. While knowledge of ascorbate biosynthesis and catabolism is rapidly expanding, little is known about the mechanisms by which ascorbate exerts its effects, and how it is regenerated. The objective of the current proposal is to determine the physiological role of a newly-identified class of membrane proteins, cytochromes (Cyts) b561, in ascorbate metabolism and regeneration, using Arabidopsis thaliana as a model system. Based on previous work, the central hypothesis is that Cyts b561 contributes to ascorbate-mediated cellular processes by catalyzing trans-membrane electron transport with ascorbate as the electron donor. Partially-oxidized ascorbate (mono-dehydroascorbate) can be re-reduced to ascorbate in this reaction, thereby replenishing cellular ascorbate pools. The objective of this proposal will be attained by: 1) determining the spatial and temporal expression patterns of A. thaliana Cyts b561; 2) determining the physiological role of Cyts b561 by altering its expression levels, and 3) determining the biochemical properties of A. thaliana Cyts b561. The proposed research is significant in that it is aimed at a class of poorly-studied membrane proteins involved in ascorbate-mediated reactions. Insight into the function of these proteins should contribute to our understanding of ascorbate regulation and metabolism in plants. Broader Impacts: The multidisciplinary approaches in the laboratory of the PI provide an opportunity for training and professional development of students and postdoctoral researchers. The PI will take part in university outreach programs to underrepresented groups, and results from this work will be broadly disseminated.