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First published online October 29, 2004; 10.1104/pp.104.049841 Plant Physiology 136:3594-3604 (2004) © 2004 American Society of Plant Biologists Deletion of the Chloroplast-Localized Thylakoid Formation1 Gene Product in Arabidopsis Leads to Deficient Thylakoid Formation and Variegated Leaves1Department of Plant Pathology (Q.W., R.W.S., K.L.K.) and Department of Biological Sciences (A.K., R.L.H.), University of Arkansas, Fayetteville, Arkansas 72701; and Department of Biology (J.H.) and Departments of Biology and Pharmacology (A.M.J.), University of North Carolina, Chapel Hill, North Carolina 27599
Development of thylakoid membranes depends upon the transport of membrane vesicles from the chloroplast inner envelope and subsequent fusion of vesicles within the interior of the plastid. The Arabidopsis (Arabidopsis thaliana) Thylakoid formation1 (Thf1) gene product is shown here to control an important step required for the normal organization of these vesicles into mature thylakoid stacks and ultimately for leaf development. The Arabidopsis Thf1 gene encodes an imported chloroplast protein, as shown by in vitro import and localization of a Thf1-green fluorescent protein fusion product in transgenic plants. This gene is conserved in oxygenic photoautotrophs ranging from cyanobacteria to flowering land plants. Transcript levels for Thf1 are induced in the light and decrease under dark conditions, paralleling profiles of light-regulated nuclear genes involved in chloroplast function. Disruption of the Thf1 gene via T-DNA insertion results in plants that are severely stunted with variegated leaf patterns. Nongreen sectors of variegated leaves lacking Thf1 expression contain plastids that accumulate membrane vesicles on the interior and lack organized thylakoid structures. Green sectors of Thf1-disrupted leaves contain some chloroplasts that form organized thylakoid membranes, indicating that an inefficient compensatory mechanism supports thylakoid formation in the absence of Thf1. Genetic complementation of a Thf1 knockout line confirms the role of this gene in chloroplast and leaf development. Transgenic plants expressing the Thf1 gene in antisense orientation are stunted with altered thylakoid organization, especially in young seedlings. The data indicate that the Thf1 gene product plays a crucial role in a dynamic process of vesicle-mediated thylakoid membrane biogenesis.
1 This work was supported in part by the Arkansas Rice Research and Promotion Board (grants to K.L.K.), by the National Institutes of Health COBRE Program of the National Center for Research Resources (grant no. P20RR15569 to R.L.H.), by the Department of Energy (grant no. DEFG0201ER15161 to R.L.H.), by the National Institute of General Medical Sciences (grant no. GM6598901 to A.M.J.), and by the National Science Foundation (grant no. MCB0209711 to A.M.J.). Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.049841. * Corresponding author; e-mail kkorth{at}uark.edu; fax 4795752771. Received July 22, 2004; returned for revision September 1, 2004; accepted September 7, 2004. This article has been cited by other articles:
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