Identification of genes differentially expressed in P. pinea and P. pinaster after infection with the pine wood nematode (PWD) using the SSH technique

Abstract

The purpose of this study was to compare the response to infection with the pine wood
nematode (PWN) Bursaphelenchus xylophilus between Pinus pinaster and Pinus pinea at an initial stage of the disease, three hours after inoculation. The PWN is the causal agent of pine
wilt disease, in Portugal its main host is the maritime pine, P. pinaster, and its vector is
Monochamus galloprovincialis. Interestingly, this disease does not seem to affect the species
P. pinea and several factors could be behind this difference in susceptibility.
At the first hours following infection by pathogens, the tree develops a hypersensitive
response, which includes the production of resistance proteins, among other compounds
crucial to the defence mechanism. Currently there are no studies that describe the effects of
nematode infection in plants at an early stage of the disease.
With regards to the physiological and metabolic indicators of the disease response in
the plants, there was a decrease of 10.9% of water content in P. pinaster (compared with trees
inoculated with water) and 6.7% in P. pinea; in the study of total chlorophyll concentration, a
decrease to about half of the control value was recorded for both species, but more
pronounced in P. pinaster. An exploratory study was also made with GC, which showed that
the volatile compounds produced were distinctive between species, but not between control
vs. nematode-inoculated plants.
With regards to the effects of the disease at a transcriptional level, the SSH technique
was utilized to identify ESTs in P. pinaster and P. pinea when inoculated with NMP. ESTs
were isolated, cloned, sequenced and identified using BlastN and BlastX, and clearly
indicated that at an initial stage of the disease there is activation of a defence response at a
molecular level, mainly related to oxidative stress, production of lignin and ethylene and posttranscriptional regulation of nucleic acids. 58% of the isolated sequences are not yet
described, which shows the lack of genomic information currently available for pine.

Date of Award	27 Apr 2012
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Marta Vasconcelos (Supervisor)