|Khajuria, Chitvan -|
|Wang, Haiyan -|
|Liu, Xuming -|
|Wheeler, Shanda -|
|Reese, John -|
|El Bohssini, Mustafa -|
|Whitworth, Jeff -|
Submitted to: Biomed Central (BMC) Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2013
Publication Date: June 26, 2013
Citation: Khajuria, C., Wang, H., Liu, X., Wheeler, S., Reese, J.C., El Bohssini, M., Whitworth, J.R., Chen, M. 2013. Defense mechanisms in resistant wheat seedlings in response to hessian fly attack. Biomed Central (BMC) Genomics. 14: 423. Interpretive Summary: Resistance is the main strategy to control Hessian fly, a destructive insect pest of wheat. However, resistance in wheat can be overcome by Hessian fly within a relatively short time, often in 6 to 8 years. A better understanding of the mechanisms of wheat resistance to Hessian fly is needed to improve durability of resistance. This study analyzed changes in gene expression in resistant and susceptible plants at different time points after Hessian fly infestation, and changes in accumulation of metabolites in those plants and time points as well. The combined analyses revealed that resources including membrane lipids, carbohydrates, and proteins/amino acids are rapidly released for active defense. The mobilized resources are likely rapidly converted into defense molecules with toxicity to the insect, or molecules that can be used to strengthen the cell wall. The combination of enhanced toxicity and strengthened cell walls are likely responsible for the death of Hessian fly larvae within plants that carry an effective resistance gene. The results provide a foundation for further research that may lead to improved durability of resistant wheat cultivars.
Technical Abstract: Wheat – Hessian fly interaction follows a typical gene-for-gene model. Hessian fly larvae die in wheat plants carrying an effective resistance gene, or thrive in susceptible plants that carry no effective resistance gene. Here we found that gene sets affected by Hessian fly attack in resistant plants were very different from those in susceptible plants. Differential expression of gene sets was associated with differential accumulation of intermediates in defense pathways. Our results indicated that resources were rapidly mobilized in resistant plants for defense, including extensive membrane remodeling and release of lipids, sugar catabolism, and amino acid transport and degradation. These resources were likely rapidly converted into defense molecules such as oxylipins; toxic proteins including cysteine proteases, inhibitors of digestive enzymes, and lectins; phenolics; and cell wall components. However, toxicity alone does not kill Hessian fly larvae. Toxic defenses might slow down Hessian fly development and therefore give plants more time for other types of defense to become effective. Evidence suggested that remodeling and fortification of cell walls by increased deposition of phenolics and enhanced cross-linking were likely to be crucial for insect mortality by depriving Hessian fly larvae of nutrients from host cells.