原花青素作为植物重要的次生代谢产物,是植物应对生物和非生物胁迫的一种重要防御手段,也是影响植物发育和品质的重要因素。原花青素作为花青素生物合成的一条末端通路在模式植物中已有研究,但是具体代谢和调控机制尚不明确;原花青素作为棕色棉纤维呈色的主要物质,其棉纤维呈色的生化与分子机制仍未完全阐明。本研究从陆地棉(Gossypium hirsutum)中克隆了一个MYB类转录因子基因GhTT2 (transparent testa 2),并对其基因结构、表达模式、亚细胞定位及功能进行了分析。结果表明：GhTT2转录因子具有典型的MYB结构域,在纤维中优势表达,其转录水平随花青素含量增加而降低;该基因可被原核诱导表达;与GFP融合的重组蛋白定位在细胞核;酵母转化结果表明GhTT2具有转录激活功能;在棉花中沉默GhTT2基因的表达,导致原花青素含量显著降低,表明其可能参与调控陆地棉原花青素的生物合成。本研究结果为深入阐明MYB类转录因子参与调控植物原花青素生物合成途径的分子机制提供参考。

As one of the important secondary metabolites, proanthocyanidins (PAs) are not only a defense mechanism for plants to cope with biotic and abiotic stresses, but also a key factor affecting the development and quality of plants. Although the biosynthetic and metabolic pathways of proanthocyanidins have been basically clarified in the model plants, the regulatory mechanism in cotton has not been fully elucidated. In this work, a transcription factor gene GhTT2 (transparent testa 2) was cloned from Gossypium hirsutum. Its gene structure, expression pattern, subcellular localization, and function were further analyzed. The results show that the GhTT2 has a typical MYB domain and is predominantly expressed in fibers. Its transcription level was negatively correlated with anthocyanin content. The GhTT2-GFP fusion protein is located in the nucleus. Moreover, yeast transformation results show that GhTT2 has obvious transcriptional activation characteristics. Furthermore, the content of proanthocyanidins in GhTT2-silenced cottons is significantly reduced, indicating that GhTT2 may be involved in regulation of the proanthocyanidins biosynthesis in Gossypium hirsutum. These results provide a reference for further elucidating the molecular mechanisms of MYB transcription factors involved in the regulation of the biosynthetic pathway of PAs.