Differential localization of Hessian Fly candidate effectors in resistant and susceptible wheat plants

Authors: AL-JBORY, ZAINAB - Kansas State University; AIKINS, MICHAEL - Kansas State University; PARK, YOONSEONG - Kansas State University; REECK, GERALD - Kansas State University; Chen, Ming-Shun

Submitted to: Plant Direct
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2020
Publication Date: 8/14/2020
Citation: Al-Jbory, Z.A., Aikins, M.J., Park, Y., Reeck, G.R., Chen, M. 2020. Differential localization of Hessian Fly candidate effectors in resistant and susceptible wheat plants. Plant Direct. https://doi.org/10.1002/pld3.246.
DOI: https://doi.org/10.1002/pld3.246

Interpretive Summary: Hessian fly, Mayetiola destructor, is a notorious pest of wheat. We tested the hypothesis that Hessian fly larvae inject small effector proteins into wheat tissues to manipulate plants to its advantage for parasitism. Our results indicated that Hessian fly larvae do indeed inject protein effectors into host plants. In resistant plants, the effectors were limited to the originally attacked cells, suggesting that limiting the spread of Hessian fly effectors within seedling tissues might be important for resistance to Hessian fly. Our finding is a step forward towards understanding the mechanisms of wheat resistance and susceptibility towards Hessian fly at the molecular level.

Technical Abstract: Hessian fly Mayetiola destructor is a notorious pest of wheat. Studies suggest that Hessian fly uses effector-based mechanisms to attack wheat plants during its parasitism, but no direct evidence has been reported to support that. Here, we produced recombinant proteins for five members of Family-1 effectors and their antibodies used for indirect immune-staining and western blotting. Our report is the first to examine localization of Hessian fly effectors in host tissues and its own tissues. Confocal images revealed that Family-1 effectors were exclusively produced in the basal region of salivary glands, which is directly linked to the mandibles’ ducts for effector injection during feeding. The five effectors were efficiently detected by western blots in host plant. Interestingly, indirect immune-staining of sectioned host tissues around the feeding site of resistant and susceptible plants revealed strikingly different localization patterns indicating to effectors trigger different plant responses. In susceptible plants, effectors penetrated deep into wheat tissue; pattern of their diffusion is an indication of nutritive cells formation at the attack site following infestation. In contrast, effectors were trapped in the initially attacked cells in four resistant wheat lines. The limitation of effectors’ spreading in resistant plants was due to wall strengthening of the attacked cells and rapid hypersensitive responses, a conserved mechanism of plant disease resistance. We also identified wheat target proteins that could elucidate potential effectors’ mechanisms of attacking crucial plant pathways. Our findings represent significant progress through visualizing detailed molecular mechanisms at the cellular level for fly effector-induced susceptibility and resistance.