How does temperature affect splicing events? Isoform switching of splicing factors regulates splicing of LATE ELONGATED HYPOCOTYL (LHY)

One of the ways in which plants can respond to temperature is via alternative splicing (AS). Previous work showed that temperature changes affected the splicing of several circadian clock gene transcripts. Here we investigated the role of RNA-binding splicing factors (SFs) in temperature-sensitive alternative splicing (AS) of the clock gene LATE ELONGATED HYPOCOTYL (LHY). We characterised, in wild type plants, temperature-associated isoform switching and expression patterns for SF transcripts from a high-resolution temperature and time series RNA-seq experiment. In addition we employed quantitative RT-PCR of SF mutant plants to explore the role of the SFs in cooling-associated AS of LHY. We show that the splicing and expression of several SFs responds sufficiently rapidly and sensitively to temperature changes to contribute to the splicing of the 5'UTR of LHY. Moreover the choice of splice site in LHY was altered in some SF mutants. The splicing of the 5'UTR region of LHY has characteristics of a molecular thermostat, where the ratio of transcript isoforms is sensitive to temperature changes as modest as 2°C and is scalable over a wide dynamic range of temperature. Our work provides novel insight into SF-mediated coupling of the perception of temperature to post-transcriptional regulation of the clock.