Cloning and Function Analysis of the TcNPR1 Gene from Taxus chinesis

Salicylic acid (SA), a common plant hormone, can increase the biosynthesis of various compounds, such as taxol in Taxus cells. NPR1 is the key gene in SA mediated plant system acquired resistance (SAR) signal pathway. To clarify the regulating mechanism of SA induced taxol biosynthesis, the TcNPR1 gene was isolated from Taxus cells, and was found to contain a 1857 bp ORF (open reading frame), which may encode a 619 aa protein. Sequence alignment showed TcNPR1 contained typical conserve domains such as Broad-Complex, Tramtrack, and Bric-a-brac/Pox virus and Zinc Finger (BTB/POZ domain), NPR1/NIM1-like-C terminal and ankyrin repeats. Phylogenetic analysis showed that TcNPR1 had a close relationship with AtNPR3 and AtNPR4 of Arabidopsis. Expression analysis revealed that the expression of the TcNPR1 gene was significantly induced by SA, drought and NaCl. In comparison to the wild type, transgenic tobacco plants over-expressing TcNPR1 showed elevated drought tolerance with soluble sugar increasing to 43.8 mg/g(FW) after 4 d of drought treatment, about two times more than the control, revealing that TcNPR1 was a functional protein. The available evidence verified that TcNPR1 may respond to SA and may be involved in systemic acquired resistance (SAR) in Taxus species. Further studies on the TcNPR1 gene are essential for clarifying its function in taxol biosynthesis.