Depletion of Atg9 and Atg2, but not Atg18, result in a macro-ER-phagy phenotype different from that of other core Atgs, and atg9∆ is epistatic to atg11∆.
A-C. While the level of overexpressed GFP-Snc1-PEM is increased in atg9∆ and atg2∆, but not atg18∆, mutant cells, it does not accumulate in aberrant structures and does not induce UPR. Wild type (WT), atg9∆, atg18∆, and atg2∆ mutant cells overexpressing GFP-Snc1-PEM were analyzed as described for Fig 1A–1C, respectively. The tested phenotypes: the level of GFP-Snc1-PEM protein (A), accumulation of GFP-Snc1-PEM in aberrant structures (B), and induction of the UPR response (C,atg1∆ is shown as a positive control). B. Shown from top to bottom: DIC, GFP, and % cells with intracellular Snc1-PEM structures. D-G. Atg9 is epistatic to Atg11 in macro-ER-phagy. ATG9 was deleted in wild type and atg11∆ mutant cells and the effects of overexpression of GFP-Snc1-PEM were determined in the single and double mutants as described in Fig 1 legend. D. Deletion of ATG9 in wild type (WT) or atg11∆ mutant cells results in an increase of GFP-Snc1-PEM protein level similar to the increase in atg11∆ mutant cells. E. Deletion of ATG9 in wild type or atg11∆ mutant cells results in an increase of intracellular GFP-Snc1-PEM fluorescence. However, only ~20% of the atg9∆ single-, and atg9∆ atg11∆ double-mutant cells accumulate GFP-Snc1-PEM in aberrant structures, as compared with ~75% of atg11∆ mutant cells. Shown from top to bottom: DIC, GFP, % cells with aberrant intracellular GFP-Snc1-PEM structures, ratio of GFP-Snc1-PEM fluorescence inside/PM (30 cells were analyzed for each strain). F. UPR is induced in atg11∆, but not in atg9∆ single- and atg9∆ atg11∆ double-mutant cells overexpressing GFP-Snc1-PEM. G. UPR can be induced in atg9∆ single-, and atg9 atg11∆ double-mutant cells overexpressing GFP-Snc1-PEM by tunicamycin. +/- and error bars represent STDEV. Results in this figure represent at least two independent experiments.