Heat stress-related Exon skip governs Serine/Arginine-rich Splicing Factor SR45a variants underlying plant heat tolerance in Arabidopsis

Heat stress seriously affects the plant development and growth. Increasing evidence points to RNA splicing as co-transcriptional regulations linking heat stresses in plants. However, the mechanism of how heat stress trigger and affect alternative splicing (AS) events through crucial splicing factors is still not clear. Here, we discovered a heat stress-enhancing AS suppression involved in splicing factor SR45a function, whereby SR45a modulates automatic self regulation by strengthen the full length mRNA processing together with CBP20. A SR45a intron splicing–dependent luciferase transgenic line was generated to monitor the intron 4 splicing events. We determined that luciferase activity increases upon heat treatment due to the intron remove, which inhibits the production of SR45a splicing variants. Loss functions of SR45a rendered plants more sensitive to heat stress, whereas overexpresion full length SR45a expression enhanced their tolerance. Full length SR45a is Essential for heat-responsive gene expression and splicing. Interestingly, SR45a modulate self-splicing regulation through branch point recognition together with CBP20. Genetic and molecular experiments identified the CBP20 is a positive regulator under heat stress. In addition, we demonstrate that HSFA2 affects the transcriptional levels of SR45a to act upsteam of SR45a by directly binding SR45a promoter. Our research highlights the heat-responsive self-splicing regulation of SR45a as a novel feedback to enhance plant stress tolerance. Wild-type, SR45a-1a overexpression lines and sr45a plants were grown on ½MS medium under LD conditions.. Two-week-old seedlings were treated with 45℃ for 3 h. Total RNA was isolated with Trizol reagen