Expression of the Thaumatin-Like Protein-1 Gene ( Bx - tlp - 1 ) from Pine Wood Nematode Bursaphelenchus xylophilus Affects Terpene Metabolism in Pine Trees.

Pine wilt disease is a major forest disease worldwide, including in China, where it has severely damaged pine forest ecosystems, and the pathogen is pine wood nematode ( Bursaphelenchus xylophilus ). The thaumatin-like protein-1 gene ( Bx - tlp - 1 ) is a key gene associated with B . xylophilus pathogenicity, which is also responsive to α-pinene. In this study, an examination of Pinus massoniana seedlings infected by B . xylophilus revealed that monoterpene (sesquiterpene) levels peaked on days 15 and 27 (days 18 and 27). Meanwhile, P . massoniana Pm - tlp expression levels were high on days 3, 12, and 27, which were consistent with the expression of key enzymes genes in the terpene biosynthesis pathway. The functional similarity of B . xylophilus Bx-TLP-1 and P . massoniana Pm-TLP suggests Bx-TLP-1 and Pm-TLP may have similar roles in P . massoniana . There was also no secondary accumulation of terpenes in P . massoniana seedlings during B . xylophilus treated with dsRNA targeting Bx - tlp - 1 (dsTLP1) infections, reflecting the decreased pathogenicity of B . xylophilus and the delayed disease progression in pine trees. And the results of micro-CT showed that the degree of cavitation for the trees inoculated with Bx-TLP-1 (0.3811 mm 3 ) was greater than that for the trees inoculated with dsTLP1 PWNs (0.1204 mm 3 ) on day 15 after inoculation. Results from this study indicated that B . xylophilus Bx - tlp - 1 gene may induce the upregulated expression of related genes encoding enzymes in the terpene synthesis pathway of P . massoniana , resulting in the accumulation of terpenes, which also provided an insight to investigate the B . xylophilus pathogenicity in the future.