Abstract
BackgroundThe interaction between insect pests and their host plants is a never-ending race of evolutionary adaption. Plants have developed an armament against insect herbivore attacks, and attackers continuously learn how to address it. Using a combined transcriptomic and metabolomic approach, we investigated the molecular and biochemical differences between Quercus robur L. trees that resisted (defined as resistant oak type) or were susceptible (defined as susceptible oak type) to infestation by the major oak pest, Tortrix viridana L.ResultsNext generation RNA sequencing revealed hundreds of genes that exhibited constitutive and/or inducible differential expression in the resistant oak compared to the susceptible oak. Distinct differences were found in the transcript levels and the metabolic content with regard to tannins, flavonoids, and terpenoids, which are compounds involved in the defence against insect pests. The results of our transcriptomic and metabolomic analyses are in agreement with those of a previous study in which we showed that female moths prefer susceptible oaks due to their specific profile of herbivore-induced volatiles. These data therefore define two oak genotypes that clearly differ on the transcriptomic and metabolomic levels, as reflected by their specific defensive compound profiles.ConclusionsWe conclude that the resistant oak type seem to prefer a strategy of constitutive defence responses in contrast to more induced defence responses of the susceptible oaks triggered by feeding. These results pave the way for the development of biomarkers for an early determination of potentially green oak leaf roller-resistant genotypes in natural pedunculate oak populations in Europe.
Highlights
The interaction between insect pests and their host plants is a never-ending race of evolutionary adaption
We demonstrated that the resistance of Resistant oak type (T-oak) to herbivore attack by T. viridana is related to the amount and scent of herbivory-induced plant volatiles (HIPVs)
A strikingly higher percentage of transcripts of the T-oak fed (TFED) < SFEDgroup were present in the MapMan functional categories (BINs) related to signalling, cell, DNA, stress, and cell wall formation compared with the TFED > S-oak fed (SFED)-group
Summary
The interaction between insect pests and their host plants is a never-ending race of evolutionary adaption. To ensure optimal defence responses, plants must be able to up- and down-regulate primary and secondary metabolic pathways at every level to exert temporal and spatial control in an effective and efficient way, thereby minimising damage and ensuring vegetative growth and reproduction [7]. For this purpose, plants have evolved constitutive and induced defence mechanisms. One of the most important groups of constitutive defence compounds that act against herbivores and pathogens are the condensed tannins (proanthocyanidins; PA) [7,9] These are polyphenolic compounds synthesised via the flavonoid biosynthetic pathway. Insect specialists prefer lower tannin content than do insect generalists [9]
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