Fig. 1.

Block in TAG synthesis disrupts the endomembrane system. a Starvation triggers alterations in the ER, Golgi, and mitochondrial morphology in cells defective in TAG synthesis (dga1Δ lro1Δ). Cells expressing indicated organelle markers were transferred from rich medium to nitrogen starvation medium. Organelle morphology was observed by fluorescent microscopy at the indicated time points. Representative images from three independent repeats are shown. DIC, differential interference contrast; Slice, a single slice in the fluorescence z-stack; Projection, max intensity projection of the fluorescence z-stack. Autophagosome*, complete or incomplete autophagosomal structure. Arrows, bulbous structures on the ER. Scale bar, 2 μm. b–d Quantification of organelle defects in a. b Number of ER bulbs per cell. c Percentage of cells displaying abnormal organelle morphology (ER bulb formation, Golgi disappearance, mitochondrial fragmentation). d Progression of autophagy defect as indicated by the decline in the number of GFP-Atg8 dots. Error bar, standard deviation, n = 3. e Inhibition of ER exit leads to disappearance of Golgi and impairment of Atg protein recruitment. sec16-ts cells expressing indicated organelle markers were first grew to mid-log phase under permissive temperature, then transferred to nitrogen starvation medium and incubated under either permissive temperature or non-permissive temperature for 1 h. Images presented as in a. f Quantification of Golgi defects in e. Error bar, standard deviation, n = 3. g Quantification of Atg1 and Atg8 recruitment defects in e. Error bar, standard deviation, n = 3