Uncoupled transcriptional and splicing responses to temperature stress in the ciliate <i>Blepharisma sinuosum</i>

Abstract Temperature is one of the most critical environmental factors influencing the physiology, ecology, and evolution of eukaryotes. As a group of single-cell protists, ciliates exhibit sensitivity to temperature fluctuations. However, their transcriptional and post-transcriptional responses to temperature stress remain unknown. Blepharisma sinuosum is a widely distributed ciliate with robust temperature adaptability. Here, we use comparative transcriptomic analyses to reveal its response strategies to temperature stresses. The results indicate that: 1) under high temperature stress, B. sinuosum tends to reduce energy expenditure and enhance its capacity to correct misfolded proteins; 2) B. sinuosum takes endocytosis and degradation of nonessential proteins to maintain cellular homeostasis in cold environments; 3) metabolic levels gradually decrease and signal transduction is progressively strengthened when temperature changes (either higher or lower); 4) splicing errors are detected under temperature stress; and 5) the regulatory mechanism of alternative splicing is not obviously connected with the transcriptional regulatory mechanism. These findings reveal how ciliates respond to temperature stress and provide new insights into the survival strategies of eukaryotes under variable environments.