STABILIZED1 Modulates Pre-mRNA Splicing for Thermotolerance.

High-temperature stress often leads to differential RNA splicing, thus accumulating different types and/or amounts of mature mRNAs in eukaryotic cells. However, regulatory mechanisms underlying plant precursor mRNA (pre-mRNA) splicing in the environmental stress conditions remain elusive. Herein, we describe that a U5-snRNP-interacting protein homolog STABILIZED1 (STA1) has pre-mRNA splicing activity for heat-inducible transcripts including s and various s for the establishment of heat stress tolerance in Arabidopsis (). Our cell-based splicing reporter assay demonstrated STA1 acts on pre-mRNA splicing for specific subsets of stress-related genes. Cellular reconstitution of heat-inducible transcription cascades supported the view that STA1-dependent pre-mRNA splicing plays a role in DREB2A-dependent expression for heat-responsive gene expression. Further genetic analysis with a loss-of-function mutant -, -expressing transgenic plants in Col background, and -expressing transgenic plants in the - background verified that STA1 is essential in expression of necessary genes including for two-step heat stress tolerance in plants. However, constitutive overexpression of the cDNA version of in the - background is unable to execute plant heat stress tolerance in - Consistently our global target analysis of STA1 showed that its splicing activity modulates a rather broad range of gene expression in response to heat treatment. The findings of this study reveal that heat-inducible STA1 activity for pre-mRNA splicing serves as a molecular regulatory mechanism underlying the plant stress tolerance to high-temperature stress.