Figure 6.

Pat1 and Scd6 are required for PB assembly in secretory transport mutants and upon Ca²⁺ treatment. (A) PBs were induced in wild type, Δpat1 or Δscd6 mutant cells expressing Dcp2-GFP by treatment with 200 mM CaCl₂ or 0.5 M NaCl, or after incubation in rich medium lacking a carbon source (−D) for 15 min at 23°C. Although PB induction by osmotic stress or starvation was not affected in the deletion mutants, a strong reduction of PB number was observed after Ca²⁺ treatment. (B) Quantification of PBs in the Δpat1 or Δscd6 strains compared with wild-type. See Figure 1B for details on the representation. (C) Pat1 and Scd6 are required for assembly of multiple PBs in secretion mutants. Wild type, arf1-11, and sec6-4 expressing Dcp2-GFP and deleted for either PAT1 or SCD6 were shifted to 37°C for 1 h. Deletion of PAT1 or SCD6 abolished the multiple PB phenotype in secretion mutants. (D) Quantification of PBs in secretory mutants deleted for PAT1 or SCD6 after a shift to the nonpermissive temperature. See Figure 1B for details on the representation. (E) PBs were induced in wild-type or arf1-11 cells expressing either Pat1-GFP or Scd6-GFP by incubation in rich medium lacking a carbon source (−D), treatment with 200 mM CaCl₂ for 15 min at 23°C, or a shift to 37°C for 1 h, respectively. Both Pat1-GFP and Scd6-GFP behaved similarly to Dcp2-GFP and were found in multiple PBs after Ca²⁺ treatment or in the secretory mutant after shift to the nonpermissive temperature. (F) arf1-11 cells deleted for PAT1 or SCD6, or carrying the cmd1-3 allele were shifted to 37°C for 1 h and their polysome profile recorded. Although all three strains do not induce multiple PBs under this condition, translation is derepressed only in the strain deleted for PAT1. Scale bars, (A, C, and E) 5 μm.