ER-associated VAP27-1 and VAP27-3 proteins functionally link the lipid-binding ORP2A at the ER-chloroplast contact sites

Luciana Renna, Giovanni Stefano, Maria Paola Puggioni, Sang-Jin Kim, Anastasiya Lavell, John E. Froehlich, Graham Burkart, Stefano Mancuso, Christoph Benning and Federica Brandizzi ()
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Luciana Renna: Michigan State University
Giovanni Stefano: Michigan State University
Maria Paola Puggioni: Michigan State University
Sang-Jin Kim: Michigan State University
Anastasiya Lavell: Michigan State University
John E. Froehlich: Michigan State University
Graham Burkart: Michigan State University
Stefano Mancuso: University of Florence
Christoph Benning: Michigan State University
Federica Brandizzi: Michigan State University

Nature Communications, 2024, vol. 15, issue 1, 1-18

Abstract: Abstract The plant endoplasmic reticulum (ER) contacts heterotypic membranes at membrane contact sites (MCSs) through largely undefined mechanisms. For instance, despite the well-established and essential role of the plant ER-chloroplast interactions for lipid biosynthesis, and the reported existence of physical contacts between these organelles, almost nothing is known about the ER-chloroplast MCS identity. Here we show that the Arabidopsis ER membrane-associated VAP27 proteins and the lipid-binding protein ORP2A define a functional complex at the ER-chloroplast MCSs. Specifically, through in vivo and in vitro association assays, we found that VAP27 proteins interact with the outer envelope membrane (OEM) of chloroplasts, where they bind to ORP2A. Through lipidomic analyses, we established that VAP27 proteins and ORP2A directly interact with the chloroplast OEM monogalactosyldiacylglycerol (MGDG), and we demonstrated that the loss of the VAP27-ORP2A complex is accompanied by subtle changes in the acyl composition of MGDG and PG. We also found that ORP2A interacts with phytosterols and established that the loss of the VAP27-ORP2A complex alters sterol levels in chloroplasts. We propose that, by interacting directly with OEM lipids, the VAP27-ORP2A complex defines plant-unique MCSs that bridge ER and chloroplasts and are involved in chloroplast lipid homeostasis.

Date: 2024
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DOI: 10.1038/s41467-024-50425-7

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