Submitted to: Arthropod-Plant Interactions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/1/2013
Publication Date: 8/1/2013
Citation: Subramanyam, S., Zheng, C., Shukle, J.T., Williams, C.E. 2013. Hessian fly larval attack triggers elevated expression of disease resistance dirigent-like protein-encoding gene, HfrDrd, in resistant wheat. Arthropod-Plant Interactions. 7:389-402. Interpretive Summary: 1. A background statement explaining the problem 2. A description of what was found, not what was done 3. A statement stating why the results are important to the producer, consumer, industry, or other user. Little is known about which mechanisms and genes wheat uses to defend itself against insect pests like the Hessian fly. One gene that responds in resistant wheat is HfrDrd, a gene that appears to be involved in structural fortification of the plant cells to make them harder for the insect to penetrate. This gene responds within 2 hours of Hessian fly attack but is non-responsive to other insect pests tested. This discovery is important because this gene can be manipulated genetically to increase cell fortification and the regulatory region of the gene may be useful in driving toxin-producing transgenes to combat Hessian fly, providing a new form of resistance.
Technical Abstract: Dirigent proteins regulate coupling of monolignol plant phenols to generate the structural cell wall polymers lignins and lignans that are involved in structural fortification of cell wall and defense against pathogens and pests. Microarray expression profiling of resistant wheat (Triticum aestivum) crown tissue revealed increased accumulation of disease resistant dirigent-like protein-encoding gene transcripts in response to infestation by Hessian fly (Mayetiola destructor), a major dipteran pest. In this study, we report the characterization and temporal expression of a putative Hessian fly-responsive disease resistance dirigent-like protein-encoding gene, HfrDrd, in wheat, under biotic (Hessian fly/aphid/virus/fall army worm/silver leaf white fly) and abiotic (mechanical wounding) stresses, as well as during treatment with signaling elicitors. Quantitative real-time transcriptional analysis indicated increased levels of HfrDrd mRNA in both compatible (susceptible) and incompatible (resistant) wheat after Hessian fly attack, however resistant wheat accumulated the highest mRNA levels. The increase in transcripts as early as 2h post egg-hatch suggests a role for HfrDrd in early defense in warding off Hessian fly larvae. HfrDrd is regulated independently of plant defense signaling pathway molecules, SA, methyl jasmonate or ABA. Lack of up-regulation of HfrDrd during other wheat-insect interactions, such as fall army worm, silverleaf whitefly and aphid infestations, indicates that HfrDrd is not a general stress-responsive gene, but is a specific defense mechanism in response to feeding by Hessian fly larvae.