Fig. 10: Model for CaLB1 function in autophagy.

CaLB1 is induced by salt and is necessary for resistance to salt stress. The C2 ___domain of CaLB1 binds the phospholipid PI(3)P and ATG8 proteins, which are present in autophagosomal membranes. This could form the basis of CaLB1 recruitment to autophagosomes. With the C-terminal IDR, CaLB1 binds the IDR of ALIX. CaLB1 can form molecular condensates on autophagosomes in conjunction with ALIX. The stimulation of condensate formation by CaLB1 may serve as a trigger for the formation of ALIX filaments, which in turn facilitates the subsequent recruitment and positioning of ESCRT-III filaments through multivalent interactions at the site of autophagosome closure. Together with other ESCRT-related proteins, CaLB1 and ALIX present important factors that coordinate autophagosome maturation in plant cells, especially under salt stress.