Intron retention via alternative splicing affects the thermotolerance regulation of ZmHsf17.

Heat shock transcription factor (Hsf) plays a pivotal role in promoting rapid heat‐induced transcriptional reprogramming in plants. The thermotolerance regulatory function of Hsfs is influenced by their own alternative splicing. In this study, we found that ZmHsf17‐II, an intron retention isoform of subclass A2 gene ZmHsf17 of maize (Zea mays), accumulated in large amounts as a result of severe or sustained heat stress. It was confirmed by expression and purification that ZmHsf17‐II encodes a small truncated peptide with 115 amino acids. ZmHsf17‐II was found to be located in the nucleus and have no transcriptional activity. Overexpressing ZmHsf17‐I in Arabidopsis could enhance plants' thermotolerance, while overexpressing ZmHsf17‐II does not. Based on the results of molecular docking, Y2H and split LUC experiments, we found that ZmHsf17‐II could bind to DBD region of ZmHsf17‐I through the hydrogen bond interaction between the truncated DBD of ZmHsf17‐II and three amino acid residues (Arg105, Thr109 and Lys142) of ZmHsf17‐I DBD region. Further experiments showed that ZmHsf17‐I could bind to its own promoter and exhibited transcriptional activation activity, while ZmHsf17‐I interaction with ZmHsf17‐II, transcriptional activation activity was interfered. Those findings indicate that ZmHsf17 can negatively regulate its own transcription by producing more intron retention isoforms via alternative splicing under heat stress. [ABSTRACT FROM AUTHOR]