VIPP1, a nuclear gene of Arabidopsis thaliana essential for thylakoid membrane formation

The conversion of light to chemical energy by the process of photosynthesis is localized to the thylakoid membrane network in plant chloroplasts, Alth ough several pathways have been described that target proteins into and acr oss the thylakoids, little is known about the origin of this membrane syste m or how the lipid backbone of the thylakoids is transported and fused with the target membrane. Thylakoid biogenesis and maintenance seem to involve the flow of membrane elements via vesicular transport. Here we show by muta tional analysis that deletion of a single gene called VIPP1 (vesicle-induci ng protein in plastids 1) is deleterious to thylakoid membrane formation. A lthough VIPP1 is a hydrophilic protein it is found in both the inner envelo pe and the thylakoid membranes. In VIPP1 deletion mutants vesicle formation is abolished. We propose that VIPP1 is essential for the maintenance of th ylakoids by a transport pathway not previously recognized.