Abstract
The tight regulation of ribosome content is one of the most important cellular resource-management strategies1,2. In the budding yeast, two sets of ribosomal protein (RP) genes, which differ mostly in the presence of introns, contribute to the expression level of ribosomes3–5. Despite recent advances on the role of introns under stress and starvation6–8, understanding the contribution of introns to ribosome regulation remains challenging. Here, combining isogrowth profiling9 with single-cell protein measurements10, we found that osmotic stress leads to bimodal expression of the small ribosomal subunit protein Rps22B mediated by intron retention in its transcript. The two resulting yeast subpopulations differ in their ability to cope with starvation. Low Rps22B protein levels implied higher survival rates under long starvation, while high Rps22B levels enabled cells to resume growth sooner after transient starvation stress. Further, yeast growing at high glucose concentrations – similar to those in ripe grapes – exhibit bimodal Rps22B expression when approaching stationary phase. Differential regulation via introns in the RP genes thus provides a way to diversify the population when approaching stationary phase in natural environments. Our findings add regulation of splicing to the known mechanisms employed by yeast to induce phenotypic heterogeneity in changing environments11,12 and suggest that duplicated RP genes serve to resolve the evolutionary conflict between precise expression control and environmental responsiveness13.
Competing Interest Statement
The authors have declared no competing interest.