Abstract
Pine wilt disease (PWD) caused by pine wood nematode (PWN), Bursaphelenchus xylophilus, is the most destructive diseases of pine and poses a threat of serious economic losses worldwide. Although several of the mechanisms involved in disease progression have been discovered, the molecular response of Pinus massoniana to PWN infection has not been explored. We constructed four subtractive suppression hybridization cDNA libraries by taking time-course samples from PWN-inoculated Masson pine trees. One-hundred forty-four significantly differentially expressed sequence tags (ESTs) were identified, and 124 high-quality sequences with transcriptional features were selected for gene ontology (GO) and individual gene analyses. There were marked differences in the types of transcripts, as well as in the timing and levels of transcript expression in the pine trees following PWN inoculation. Genes involved in signal transduction, transcription and translation and secondary metabolism were highly expressed after 24 h and 72 h, while stress response genes were highly expressed only after 72 h. Certain transcripts responding to PWN infection were discriminative; pathogenesis and cell wall-related genes were more abundant, while detoxification or redox process-related genes were less abundant. This study provides new insights into the molecular mechanisms that control the biochemical and physiological responses of pine trees to PWN infection, particularly during the initial stage of infection.
Highlights
Pine wilt disease (PWD) is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus, which is believed to be native to North America
To identify the P. massoniana genes that were differentially expressed during the early response stages of PWN inoculation, four suppression subtractive hybridization (SSH) libraries were constructed using mRNAs from PWN-inoculated and water-inoculated stems that were sampled at 24 h and 72 h after inoculation (PM-24h and PM-72h, respectively)
These results suggest that genes involved in responses to stress and secondary metabolism were expressed in the early stage of the P. massoniana response to PWN infection
Summary
Pine wilt disease (PWD) is caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus, which is believed to be native to North America. PWD only damaged exotic pine trees in North America, but it has recently spread to Asian and European countries, including Japan, China, South Korea and Portugal, and PWN was recently reported in. PWD is the most destructive pine disease, causing significant economic losses around the world, especially in Asia. PWD kills 1,000,000 m3 of pine trees annually in Japan [4] and damaged approximately 7811 ha of pines in Korea by 2005 [5]. In China, economic losses due to PWD were estimated to be 2.5 billion Chinese RMB (approximately 400 million USD) [6]. Despite many advances on the study of PWD, the pathogenic mechanism of PWD has not been clearly defined
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