Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2011
Publication Date: 6/13/2011
Citation: Williams, C.E., Shukle, J.T., Nemacheck, J.A., Subramanyam, S., Saltzmann, K., Shukle, R.H. 2011. Induced epidermal permeability modulates resistance and susceptibility of wheat seedlings to herbivory by Hessian fly larvae. Journal of Experimental Botany. 63:4521-4531. Interpretive Summary: Hessian fly larvae attack wheat plants and are able to imbibe cell contents including nutrients (susceptible plants) or defense molecules (resistant plants). But since the larvae are unable to chew holes or puncture the epidermal cells of the plant, mechanisms for delivery of plant liquids were unknown. We found that both virulent and avirulent larvae cause changes in the surface permeability of plants that are capable of delivering cell contents to the larvae. The extent of permeability increases over time in susceptible plants. But permeability persists just long enough to deliver defense molecules in resistant plants, which then repair the damage. The result is that during coinfestation of plants by both virulent and avirulent larvae, the spreading permeability is able to rescue the avirulent larvae so that more Hessian flies survive. This keeps greater genetic diversity in the population of Hessian flies.
Technical Abstract: Salivary secretions of neonate Hessian fly larvae initiate epidermal permeability in wheat plants, resulting in the two-way exchange of molecules. This permeability allows larval elicitors to enter the plant where they can trigger plant processes leading to resistance or susceptibility. The rapid increase in cell permeability allows the delivery of either plant defense molecules as incompatible interactions proceed or nutrients for larval consumption during compatible interactions. Resistant plants remain permeable just long enough to deliver molecules that kill the larvae. In contrast, susceptible plants continue to increase in permeability until the entire crown of the plant becomes a nutrient sink capable of overwhelming any localized defense response. The three-dimensional spreading of permeability initiated by virulent larvae within a few hours of attack rescues genetically avirulent larvae that may be present and sustains larval growth until nutritive tissue is established.