Skip to main content
ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #208046
Title: A Novel Nucleus-encoded Chloroplast Protein, PIFI, Is Involved in NAD(P)H Dehydrogenase Complex Mediated Chlororespiratory and Possibly Cyclic Electron Transport in Arabidopsis

Author
item WANG, DAFU - UNIVERSITY OF ILLINOIS
item Portis Jr, Archie

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2007
Publication Date: 6/15/2007
Citation: Wang, D., Portis Jr, A.R. 2007. A novel nucleus-encoded chloroplast protein, PIFI, is involved in NAD(P)H dehydrogenase complex mediated chlororespiratory and possibly cyclic electron transport in Arabidopsis. Plant Physiology. 144:1742-1752.

Interpretive Summary: In addition to photosynthetic electron transport, a respiratory electron flow called chlororespiration occurs in the chloroplasts, which can be monitored by a transient rise in chlorophyll fluorescence after a light-to-dark transition. This process is dependent on the activity of a chloroplast membrane complex (NDH). In this study, we characterized an Arabidopsis thaliana mutant named pifi, which lacks a soluble stromal protein and the NDH-dependent chlorophyll fluorescence increase after a light-to-dark transition but possesses an intact NDH complex. The pifi mutant grows normally under low-light conditions but exhibits a greater sensitivity to photoinhibition and long-term mild heat stress than wild type plants. We conclude that PIFI is a novel component essential for chlororespiration and is likely to be involved in the NDH-mediated cyclic electron transport pathway in higher plants. This information will benefit scientists in better understanding the roles of chlororespiration and cyclic electron transport in plant metabolism.

Technical Abstract: A transient rise in chlorophyll fluorescence after a light-to-dark transition reflects non-photochemical reduction of the plastoquinone pool. This process is dependent on the activity of the chloroplast NAD(P)H-dehydrogease complex (NDH) which mediates electron flow from stromal reductants to the plastoquinone pool. In this study, we characterized an Arabidopsis thaliana T-DNA insertion mutant pifi (post-illumination chlorophyll fluorescence increase), which lacks the NDH-dependent chlorophyll fluorescence increase after a light-to-dark transition but possesses an intact NDH complex. The nuclear gene PIFI (At3g15840) containing the T-DNA insertion encodes a chloroplast-targeted protein localized in the stroma and is annotated as a protein of unknown function. The pifi mutant exhibited a lower capacity for thermal dissipation (NPQ) but similar PSII quantum efficiencies ( PSII) and a slight reduction in levels of the primary electron acceptor of PSII (1-qP) as compared with the wild type. The pifi mutant grows normally under low-light conditions but exhibits a greater sensitivity to photoinhibition and long-term mild heat stress than wild type plants, suggesting that PSI cyclic electron flow could be impaired. Impaired PSI cyclic electron flow was also indicated by a lower oxidation level of the photosystem I reaction center in the pifi mutant than wild type. We conclude that PIFI is a novel component essential for NDH-mediated non-photochemical reduction of the plastoquinone pool in chlororespiration and is likely to be involved in the NDH-mediated cyclic electron transport pathway in higher plants.