The alternative splicing ofZmHsf23regulates heat stress tolerance in maize

Abstract

SummaryHeat stress is one of the major threats to maize (Zea mays) production globally. Heat shock transcription factors (HSFs) play vital roles in plant heat stress responses. However, the molecular and genetic basis of HSFs in maize thermotolerance remain largely unknown.In this study, we reveal that the alternative splicing ofHsf23in maize modulates heat stress tolerance.Hsf23produces two functional transcripts, the full-length transcriptHsf23band the heat-inducible transcriptHsf23a. The twoHsf23transcripts differ by the presence of a cryptic mini exon inHsf23a, which is spliced out inHsf23b. BothHsf23aandHsf23bwere intensely expressed in response to heat stress.The overexpression ofHsf23b, notHsf23a, enhanced heat stress tolerance, while loss-of-function mutations ofHsf23aandHsf23bexhibited remarkably increased sensitivity to heat stress. Transcriptome analysis revealed that Hsf23b activates broader heat-responsive genes than Hsf23a, and Hsf23a and Hsf23b modulate heat stress response through different downstream targets. Furthermore, Hsf23a physically interacted with Hsf23b and promotes Hsf23b-regulated expression ofsHSPgenes.Together, our finding provides new insights into the roles ofZmHsf23in the heat tolerance in maize, and presents an important candidate for the genetic improvement of heat-tolerant maize varieties.