ARS | Publication request: Aphid Feeding Activates Expression of a Transcriptome of Oxylipin-Based Defense Signals in Wheat Involved in Resistance to Herbivory

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2010
Publication Date: February 21, 2010
Citation: Smith, C., Liu, X., Wang, L., Liu, X., Chen, M., Starkey, S., Bai, J. 2010. Aphid Feeding Activates Expression of a Transcriptome of Oxylipin-Based Defense Signals in Wheat Involved in Resistance to Herbivory. Journal of Chemical Ecology. 36:260-276.

Interpretive Summary: The Russian wheat aphid (RWA), Diuraphis noxia, significantly reduces wheat and barley yields worldwide. Host plant resistance is one of the methods for controlling the damage caused by this pest. A better understanding of the molecular aspects of arthropod resistant plants may result in the improvement of the host plant resistance strategy in integrated pest management. This research was conducted to identify genes and other products that are differentially regulated in resistant and susceptible plants in responding to RWA attacks, using microarray and other technologies. We found that RWA-infested resistant plants upregulated >180 genes related to various defense processes. These genes were either not upregulated or delayed in production in susceptible plants when they were attacked by RWA. Further research on these differentially expressed genes should result in a better understanding of the molecular mechanisms in wheat resistance to RWA, which may eventually lead to more durable resistance.

Technical Abstract: Damage by the Russian wheat aphid (RWA), Diuraphis noxia, significantly reduces wheat and barley yields worldwide. In compatible interactions, virulent RWA populations flourish and susceptible plants suffer extensive leaf chlorophyll loss. In incompatible interactions, RWA reproduction and population growth are significantly reduced and RWA related chlorophyll loss in resistant plants is minor. The objectives of this study were to develop an understanding of the molecular and phytochemical bases of RWA resistance in plants containing the Dnx resistance gene. Microarray, real-time polymerase chain reaction, and phytohormone assays were conducted to identify transcriptome components unique to RWA infested Dnx plants and susceptible (Dn0) plants, and to identify and characterize putative genes involved in Dnx plant defense responses. We found that RWA-infested Dnx plants upregulated >180 genes related to reactive oxygen species, signaling, pathogen defense, and arthropod allelochemical and physical defense. The expression of several of these genes in RWA-infested Dnx plants increased significantly from 6- to 24-hr post infestation (hpi), but their expression in Dn0 plants, when present, was delayed until 48- to 96 hpi. Concentrations of 16- and 18-carbon fatty acids, trans- methyl-12-oxophytodienoic acid, and abscisic acid were significantly greater in Dnx foliage than in Dn0 foliage after RWA infestation, suggesting that Dnx RWA defense and resistance genes may be regulated via the oxylipin pathway. These findings provide a foundation for the elucidation of the molecular basis for compatible- and incompatible plant aphid interactions.