Activation of defence pathways in Scots pine bark after feeding by pine weevil (Hylobius abietis).
BACKGROUND
During their lifetime, conifer trees are exposed to numerous herbivorous insects. To protect themselves against pests, trees have developed a broad repertoire of protective mechanisms. Many of the plant's defence reactions are activated upon an insect attack, and the underlying regulatory mechanisms are not entirely understood yet, in particular in conifer trees. Here, we present the results of our studies on the transcriptional response and the volatile compounds production of Scots pine (Pinus sylvestris) upon the large pine weevil (Hylobius abietis) feeding.


RESULTS
Transcriptional response of Scots pine to the weevil attack was investigated using a novel customised 36.4 K Pinus taeda microarray. The weevil feeding caused large-scale changes in the pine transcriptome. In total, 774 genes were significantly up-regulated more than 4-fold (p≤0.05), whereas 64 genes were significantly down-regulated more than 4-fold. Among the up-regulated genes, we could identify genes involved in signal perception, signalling pathways, transcriptional regulation, plant hormone homeostasis, secondary metabolism and defence responses. The weevil feeding on stem bark of pine significantly increased the total emission of volatile organic compounds from the undamaged stem bark area. The emission levels of monoterpenes and sesquiterpenes were also increased. Interestingly, we could not observe any correlation between the increased production of the terpenoid compounds and expression levels of the terpene synthase-encoding genes.


CONCLUSIONS
The obtained data provide an important insight into the transcriptional response of conifer trees to insect herbivory and illustrate the massive changes in the host transcriptome upon insect attacks. Moreover, many of the induced pathways are common between conifers and angiosperms. The presented results are the first ones obtained by the use of a microarray platform with an extended coverage of pine transcriptome (36.4 K cDNA elements). The platform will further facilitate the identification of resistance markers with the direct relevance for conifer tree breeding.
Department of Forest Sciences, University of Helsinki, P.O. Box 27, FIN-00014, Helsinki, Finland. Andriy.Kovalchuk@helsinki.fi.
Andriy
A
Kovalchuk
Department of Forest Sciences, University of Helsinki, P.O. Box 27, FIN-00014, Helsinki, Finland. Tommaso.Raffaello@helsinki.fi.
Tommaso
T
Raffaello
Department of Forest Sciences, University of Helsinki, P.O. Box 27, FIN-00014, Helsinki, Finland. Emad.Jaber@helsinki.fi.
Emad
E
Jaber
Department of Forest Sciences, University of Helsinki, P.O. Box 27, FIN-00014, Helsinki, Finland. Susanna.Kerio@helsinki.fi.
Susanna
S
Keriö
Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FIN-70211, Kuopio, Finland. Rajendra.Ghimire@uef.fi.
Rajendra
R
Ghimire
Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA, 30602, USA. wlorenz@uga.edu.
W Walter
WW
Lorenz
Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, GA, 30602, USA. jeffdean@bch.msstate.edu.|Department of Biochemistry, Molecular Biology, Entomology & Plant Pathology, Mississippi State University Mississippi State, Mississippi, MS, 397672, USA. jeffdean@bch.msstate.edu.
Jeffrey F D
JF
Dean
Department of Environmental Science, University of Eastern Finland, P.O. Box 1627, FIN-70211, Kuopio, Finland. Jarmo.Holopainen@uef.fi.
Jarmo K
JK
Holopainen
Department of Forest Sciences, University of Helsinki, P.O. Box 27, FIN-00014, Helsinki, Finland. Fred.Asiegbu@helsinki.fi.
Fred O
FO
Asiegbu
D000818:Animals; D002473:Cell Wall / Q000378:metabolism; D004435:Eating; D020869:Gene Expression Profiling; D060434:Herbivory; D006706:Homeostasis; D028223:Pinus / Q000166:cytology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D024301:Plant Bark / Q000166:cytology / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010937:Plant Growth Regulators / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D055549:Volatile Organic Compounds / Q000378:metabolism; D048889:Weevils / Q000502:physiology*
D010937:Plant Growth Regulators; D055549:Volatile Organic Compounds