Cloning and characterization of the BZR1-2 promoter from Camellia sinensis and its responses to hormonal and abiotic stresses

Tea plant ( Camellia sinensis (L.) O. Kuntze) is an important woody economic crop that has been cultivated worldwide. Adversity stress acts as a significant factor affecting the growth and development of tea plants. Brassinazole-resistant (BZR) family protein is an essential factor in regulating plant stress resistance and plays a key role in cold stress response, heat, drought and salt resistances. In this study, the promoter region upstream of CsBZR1-2 was cloned. The promoter sequence and its 5′-end truncated segment were inserted upstream of β-glucuronidase ( GUS ) gene in the pCambia1391Z plasmid. Stably expressed transgenic tobacco lines were obtained by Agrobacterium tumefaciens -mediated genetic transformation. The results showed that except for promoter lacking the core element, both full-length and truncated promoters could initiate the expression of GUS , but the level of expression was affected by the degree of deletion at the 5′-end. The core region of the promoter was in a 311 bp region including the transcription start site (TSS). In addition, the regulatory mechanism of the promoter was explored. It was found that the genes regulated by the promoter were responsive to stress such as cis-acting elements (MeJA, ABRE and LTR), BR and light. This paper provides a theoretical basis to further explore the regulatory mode of the promoter and to achieve efficient gene expression.