MOLECULAR AND GENETIC MECHANISMS OF HESSIAN FLY RESISTANCE IN SOFT WINTER WHEAT
Location: Crop Production and Pest Control Research
Title: Changes in the Properties of Wheat Leaf Cuticle During Interactions with Hessian Fly
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 26, 2010
Publication Date: June 17, 2010
Citation: Kosma, K., Nemacheck, J.A., Jenks, M., Williams, C.E. 2010. Changes in the Properties of Wheat Leaf Cuticle During Interactions with Hessian Fly. Plant Journal. 63:31-43.
Interpretive Summary: Susceptible wheat plants deliver nutrients to Hessian fly larvae via increased permeability of epidermal cells at the larval feeding site. Yet the mechanisms involved in these physical changes are unknown, as are mechanisms that help resistant plants maintain epidermal cell integrity. We demonstrated that quantities of wheat cuticular waxes and cutins as well as the expression of genes involved in their synthesis decrease over the first 8 days of larval attack in susceptible plants. These decreases are not seen in plants with induced resistance, which are able to maintain cuticle structure and increase the deposition of certain critical classes of wax that may function as feeding deterrents. Genetic and molecular manipulation of components of plant cuticle may provide a stronger physical barrier that, coupled with biochemical plant defenses, can increase the durability of deployed resistance genes in wheat cultivars.
Infestation of wheat by Hessian fly larvae causes a variety of physiological and biochemical changes in the host plant. We report here that these include changes in cuticle permeability, lipid composition and gene transcript abundance and that these responses differ substantially between resistant and susceptible wheat lines. Permeability assays revealed that susceptible plants exhibited a substantial and generalized increase in sheath epidermal permeability during infestation; whereas, epidermal permeability was only minimally affected in resistant plants. Furthermore, temporal profiling using gas chromatographic methods revealed that changes in cuticle lipid (wax and cutin) composition correlated well with differing levels of epidermal permeability in susceptible and resistant plants. Temporal analysis of cuticle-associated gene mRNA levels, by quantitative real-time PCR, indicated a relationship between transcript abundance and changes in cuticle lipid profiles of resistant and susceptible plants. Results suggest that conserving cuticle integrity via induction of specific wax constituents and maintenance of cutin amounts, as determined by the accumulation of cuticle-associated transcripts, could be important components of wheat resistance to Hessian fly larvae.