PhDREB1-PhZFP1-PhGolS1-1 regulator cascade contribute to cold tolerance by mediating galactinol and raffinose accumulation in petunia

Abstract

The C-repeat/DRE Binding Factor (CBF/DREB1) gene, which plays a critical role in plant responses to cold stress, could positively regulate the accumulation of galactinol and raffinose, but the underlying molecular mechanisms remain elusive. We have previously confirmed that the C2H2-type zinc finger protein PhZFP1 plays a positive role in cold stress tolerance by modulating galactinol accumulation by directly regulating PhGolS1-1 in Petunia hybrida. However, whether and how CBF/DREB1 regulates PhZFP1 to mediate galactinol accumulation under cold stress remains largely unclear. Here, we report the biological and molecular characterization of PhDREB1F and PhDREB1I in petunia. We demonstrate that PhDREB1F and PhDREB1I function as nuclear transcription factors and activate PhZFP1 expression. Silencing of PhDREB1F or PhDREB1I mediated by virus-induced gene silencing (VIGS) increased the sensitivity to freezing stress in petunia plants. Besides, knocking-down of PhDREB1F or PhDREB1I decreased the expression of PhZFP1 and PhGolS1-1. Similarly, silencing of PhGolS1-1 increased cold sensitivity in petunia. And the contents of galactinol and raffinose in PhGolS1-1-VIGS plants were significantly decreased compared with those in TRV plants under chilling stress. What's more, PhDREB1F/1I, PhZFP1, and PhGolS1-1 all showed cold-induced expression patterns with different peaks. Collectively, our data indicate that PhDREB1F and PhDREB1I positively modulate cold stress tolerance through the PhDREB1s-PhZFP1-PhGolS1–1 pathway in petunia. This study provides new insights into the molecular mechanism of plant responsiveness to cold stress through CBF/DREB1 transcription factors.