Alternative Splicing of TaHsfA2-7 Is Involved in the Improvement of Thermotolerance in Wheat

Abstract

High temperature has severely affected plant growth and development, resulting in reduced production of crops worldwide, especially wheat. Alternative splicing (AS), a crucial post-transcriptional regulatory mechanism, is involved in the growth and development of eukaryotes and the adaptation to environmental changes. Previous transcriptome data suggested that heat shock transcription factor (Hsf) <i>TaHsfA2-7</i> may form different transcripts by AS. However, it remains unclear whether this post-transcriptional regulatory mechanism of <i>TaHsfA2-7</i> is related to thermotolerance in wheat (<i>Triticum aestivum</i>). Here, we identified a novel splice variant, <i>TaHsfA2-7-AS</i>, which was induced by high temperature and played a positive role in thermotolerance regulation in wheat. Moreover, TaHsfA2-7-AS is predicted to encode a small truncated TaHsfA2-7 isoform, retaining only part of the DNA-binding domain (DBD). <i>TaHsfA2-7-AS</i> is constitutively expressed in various tissues of wheat. Notably, the expression level of <i>TaHsfA2-7-AS</i> is significantly up-regulated by heat shock (HS) during flowering and grain-filling stages in wheat. Further studies showed that TaHsfA2-7-AS was localized in the nucleus but lacked transcriptional activation activity. Ectopic expression of <i>TaHsfA2-7-AS</i> in yeast exhibited improved thermotolerance. Compared to non-transgenic plants, overexpression of <i>TaHsfA2-7-AS</i> in <i>Arabidopsis</i> results in enhanced tolerance to heat stress. Simultaneously, we also found that TaHsfA1 is directly involved in the transcriptional regulation of <i>TaHsfA2-7</i> and <i>TaHsfA2-7-AS</i>. In summary, our findings demonstrate the function of <i>TaHsfA2-7-AS</i> splicing variant in response to heat stress and establish a link between regulatory mechanisms of AS and the improvement of thermotolerance in wheat.