Plant autophagosomes mature into amphisomes prior to their delivery to the central vacuole

Zhao et al. reveal amphisome compartments in plant cells. By characterizing the autophagy adaptor CFS1 that can interact with both ATG8, and the ESCRT-I complex subunit VPS23A; they show that autophagosomes are sorted at amphisomes before arriving their final destination, the central vacuole. Autophagosomes are double-membraned vesicles that traffic harmful or unwanted cellular macromolecules to the vacuole for recycling. Although autophagosome biogenesis has been extensively studied, autophagosome maturation, i.e., delivery and fusion with the vacuole, remains largely unknown in plants. Here, we have identified an autophagy adaptor, CFS1, that directly interacts with the autophagosome marker ATG8 and localizes on both membranes of the autophagosome. Autophagosomes form normally in Arabidopsis thaliana cfs1 mutants, but their delivery to the vacuole is disrupted. CFS1's function is evolutionarily conserved in plants, as it also localizes to the autophagosomes and plays a role in autophagic flux in the liverwort Marchantia polymorpha. CFS1 regulates autophagic flux by bridging autophagosomes with the multivesicular body-localized ESCRT-I component VPS23A, leading to the formation of amphisomes. Similar to CFS1-ATG8 interaction, disrupting the CFS1-VPS23A interaction blocks autophagic flux and renders plants sensitive to nitrogen starvation. Altogether, our results reveal a conserved vacuolar sorting hub that regulates autophagic flux in plants.

Automated summary

The research reveals the presence of amphisome compartments in plant cells, which play a crucial role in the maturation and fusion of autophagosomes with vacuoles.