The phospholipase B homolog Plb1 and the cAMP-dependent protein kinase (PKA) pathway are required by fission yeast, also known as to Schizosaccharomyces pombe, to grow under KCl-stress conditions. Here, we report the relative contributions of Plb1 and the cAMP/PKA pathway during the hypertonic stress response. We show that the plb1∆, cyr1∆, and pka1∆ single mutants are sensitive to high concentrations of KCl but insensitive to sorbitol-induced osmotic stress. In contrast, the plb1∆ cyr1∆ and plb1∆ pka1∆ double mutants are hypersensitive to KCl and sorbitol. The cyr1∆ pka1∆ double mutants showed the same phenotype of each single mutant. Growth inhibition due to hypertonic stress in the plb1∆, plb1∆ cyr1∆, and plb1∆ pka1∆ strains was partially rescued by cgs1 deletion—cgs1∆ has constitutively active Pka1—or by the deletion of transcription factor Rst2, which is negatively regulated by Pka1. Pka1-GFP localized in the nucleus and cytoplasm in plb1∆, whereas it is localized only in the cytoplasm in cyr1∆, indicating that Plb1 does not regulate Pka1 localization. Glucose limitation downregulates the PKA pathway, and it was accordingly observed that glucose limitation in plb1∆ further increased the strain’s sensitivity to KCl. Growth inhibition by KCl in plb1∆ under glucose-limited conditions was significantly rescued by cgs1∆ and slightly rescued by rst2∆. These findings indicate that, in fission yeast, Plb1 and the glucose-sensing cAMP/PKA pathway play a synergistic role in responding to hypertonic stress.

裂殖酵母（也称为粟酒裂殖酵母）需要磷脂酶 B 同源物 Plb1 和 cAMP 依赖性蛋白激酶 (PKA) 途径才能在 KCl 胁迫条件下生长。在这里，我们报告了 Plb1 和 cAMP/PKA 通路在高渗应激反应过程中的相对贡献。我们发现plb1Δ、cyr1Δ和pka1Δ单突变体对高浓度 KCl 敏感，但对山梨醇诱导的渗透应激不敏感。相反，plb1Δ cyr1Δ和plb1Δ pka1Δ双突变体对 KCl 和山梨醇过敏。 cyr1Δ pka1Δ双突变体显示出与每个单突变体相同的表型。plb1Δ、plb1Δ cyr1Δ和plb1Δ pka1Δ菌株中高渗应激引起的生长抑制通过cgs1删除（cgs1Δ具有组成型活性 Pka1）或通过删除转录因子 Rst2（受蛋白激酶A1。plb1Δ中 Pka1-GFP 定位于细胞核和细胞质，而cyr1Δ中 Pka1-GFP 仅定位于细胞质，表明 Plb1 不调节 Pka1 定位。葡萄糖限制下调了 PKA 途径，因此观察到plb1Δ中的葡萄糖限制进一步增加了菌株对 KCl 的敏感性。在葡萄糖限制条件下， KCl 在plb1Δ中的生长抑制作用被cgs1Δ显着挽救，并被rst2Δ轻微挽救。这些发现表明，在裂殖酵母中，Plb1 和葡萄糖感应 cAMP/PKA 通路在应对高渗应激中发挥协同作用。