Alternative splicing diversifies HSF1 function to enable desiccation tolerance of P. vanderplanki cells

Heat shock factor 1 (HSF1) is a transcription factor that contributes to induction of desiccation tolerance and allow larvae of Polypedilum vanderplanki successfully enter anhydrobiosis state. Here we report the identification of five alternative splicing isoforms of P. vanderplanki HSF1 (PvHSF1) and their distinct functional roles during anhydrobiosis cycle and heat shock in Pv11 cells, derived from P. vanderplanki. All five PvHSF1 isoforms induced desiccation tolerance, but with varible efficiency followed by distinct gene expression patterns. We revealed that PvHSF1 isoform 2 is the most abundant isoform in the anhydrobiosis state. It directly regulates gene esxpression resulting in both activation and suppression. Other two PvHSF1 isoforms (1 and 3) were responsible for cell adaptation to severe heat shock by modulating expression of genes. Importantly, none of Drosophila melanogaster HSF1 (DmHSF1) splicing isoforms were able to induce the desiccation tolerance tolerance, while one DmHSF1 isoform (a) resulted in Pv11 cells survival after heat shock. Our results demonstrate that PvHSF1 splicing isoforms possess distinct regulatory roles in anhydrobiosis and heat shock to cope with different stress conditions. Overall design: mRNA-seq profiles for WT, HSF1-KO and PvHSF1- and DmHSF1- isoforms expressing Pv11 cells with trehalose treatment for 48h, rehydration for 24h and heat shock for 6h.