Developmental cellSep 12, 2025

Clusters of ATG18 change the plant cell's protein-making system to support cell recycling

Longevity & Aging Weekly Brief ↗PubMed ↗DOI ↗

Updated Jan 7, 2026

Abstract

Arabidopsis autophagy-related protein 18a (ATG18a) forms biomolecular condensates on the endoplasmic reticulum (ER) membrane during autophagosome formation.

ATG18a undergoes phase separation to create structures that transition from mobile droplets to stable rings on the ER membrane.
Biomolecular condensates of ATG18a interact with ROOT HAIR DEFECTIVE3 (RHD3), a protein that shapes the ER membrane.
RABC1 acts as a molecular linker between ATG18a condensates and RHD3, facilitating ER structure formation.
RABC1 is essential for both assembling RHD3 into ring-like structures and enabling its interaction with ATG18a.

Simplified

Autophagosomes originate from and maintain association with the endoplasmic reticulum (ER) during their formation, yet how these processes are molecularly coordinated in plants remains poorly understood. Here, we demonstrate that Arabidopsis autophagy-related protein 18a (ATG18a), a key organizer of early autophagosome formation, undergoes phase separation to form biomolecular condensates on the ER membrane, which progress from highly mobile droplets to stable ring-like structures, while the ER is reshaped. We discovered that ATG18a condensates work together with ROOT HAIR DEFECTIVE3 (RHD3), an ER membrane-shaping protein, with RABC1 serving as a molecular linker between them. Importantly, RABC1 facilitates both RHD3 assembly necessary for the formation of ring-like ER structures and its interaction with ATG18a condensates. These findings reveal a mechanism whereby biomolecular condensates work together with membrane-shaping proteins to reshape specialized membrane domains through wetting interactions, providing an insight into autophagosome formation in plant stress responses.

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Declaration of interests The authors declare no competing interests.

PubMed

Clusters of ATG18 change the plant cell's protein-making system to support cell recycling

Abstract

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