A VIPP1-associated protein VIA1 involved in thylakoid membrane biogenesis diversifies the chloroplast ESCRT landscape

Thylakoid membranes are the site of light-dependent photosynthetic reactions within chloroplasts. Instant remodeling of chloroplast membranes is essential for the biogenesis and maintenance of the thylakoid network. However, the molecular mechanisms underlying membrane remodeling in chloroplasts remain poorly understood. VIPP1, an ESCRT-III protein, is one of the few known factors directly involved in this process. To identify additional proteins, we performed a co-immunoprecipitation assay using AtVIPP1-YFP as bait, expressed in Arabidopsis. This led to the discovery of several VIPP1-interacting partners, including a previously uncharacterized winged-helix domain-containing protein, VIPP1-Associated 1 (VIA1). The interaction interface between VIPP1 and VIA1 resembles that of ESCRT-III and ESCRT-II components. The loss of VIA1 results in delayed chloroplast maturation in newly emerging leaf tissue. The phenotypic defects in the Arabidopsis via1 mutant could be complemented with VIA1 from either Arabidopsis or Chlamydomonas, underscoring its functional conservation. This study establishes VIA1 as an integral component of a chloroplast-specific ESCRT-like membrane remodeling system.