Identification of genes differentially expressed in Pinus pinaster and Pinus pinea after infection with the pine wood nematode

The purpose of this study was to compare the response to infestation by the pine wood nematode (PWN) Bursaphelenchus xylophilus between Pinus pinaster and P. pinea at an initial stage of the disease, 3 h after inoculation. The PWN is the causal agent of pine wilt disease and is destroying pine forests all over the world. In Portugal its main host is the maritime pine, P. pinaster, and its vector is the longhorn beetle Monochamus galloprovincialis. Interestingly, this disease does not seem to affect the species P. pinea and several factors could be behind this difference in susceptibility. With regards to the effects of the disease at a transcriptional level, the suppression subtractive hybridization (SSH) technique was utilized to identify Expressed Sequence Tags (EST) in P. pinaster and P. pinea when inoculated with PWN. EST were isolated, cloned, sequenced and identified using BlastN and BlastX, and indicated that at an initial stage of the disease there is activation of a tree defence response at a molecular level, mainly related to oxidative stress, production of lignin and ethylene and post-transcriptional regulation of nucleic acids. 58% of the isolated sequences are not yet described, which shows the lack of genomic information currently available for pine.