Abstract
A proteomic study was conducted to investigate physiological factors affecting feeding behaviour by larvae of the insect, Plutella xylostella, on herbivore-susceptible and herbivore-resistant Arabidopsis thaliana. The leaves of 162 recombinant inbred lines (Rils) were screened to detect genotypes upon which Plutella larvae fed least (P. xylostella-resistant) or most (P. xylostella-susceptible). 2D-PAGE revealed significant differences in the proteomes between the identified resistant and susceptible Rils. The proteomic results, together with detection of increased production of hydrogen peroxide in resistant Rils, suggest a correlation between P. xylostella resistance and the production of increased levels of reactive oxygen species (ROS), in particular H2O2, and that this was expressed prior to herbivory. Many of the proteins that were more abundant in the Plutella-resistant Rils are known in other biological systems to be involved in limiting ROS damage. Such proteins included carbonic anhydrases, malate dehydrogenases, glutathione S-transferases, isocitrate dehydrogenase-like protein (R1), and lipoamide dehydrogenase. In addition, patterns of germin-like protein 3 isoforms could also be indicative of higher levels of reactive oxygen species in the resistant Rils. Consistent with the occurrence of greater oxidative stress in the resistant Rils is the observation of greater abundance in susceptible Rils of polypeptides of the photosynthetic oxygen-evolving complex, which are known to be damaged under oxidative stress. The combined results suggest that enhanced production of ROS may be a major pre-existing mechanism of Plutella resistance in Arabidopsis, but definitive corroboration of this requires much further work.
Highlights
Plutella xylostella, the Diamondback Moth, is a specialist herbivore that feeds on species within the Brassicaceae family, including Arabidopsis thaliana [1]
In order to correlate differences in physiology to P. xylostella-resistance or susceptibility, we have used 2D-PAGE coupled with MS/MS to identify leaf proteins from A. thaliana recombinant inbred lines (Rils)
For each assay a control Ril (Ril 94) was assayed each time to account for possible inter-batch experimental differences
Summary
The Diamondback Moth, is a specialist herbivore that feeds on species within the Brassicaceae family, including Arabidopsis thaliana [1]. The A. thaliana - P. xylostella interaction is a model system used to investigate insect resistance in plants, in particular the analysis of inducible defence mechanisms [5]. Such studies have the advantage that comparisons can be made within genotypes before and after insect challenge The current study has examined traits that are pre-existing prior to herbivory and are essentially constitutive The analysis of pre-existing differences in the physiology of A. thaliana that influence insect resistance encounters some complications, including correlating similarities or differences between genotypes that relate to insect herbivory rather than to some other uncorrelated aspect of plant physiology/structure, and this is especially relevant for a proteomic study. There are many ecotypes of A. thaliana that differ widely in genotype and phenotype: as expected, this extends to differences in both protein spot expression and protein spots identified in root proteomes [8]
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