A novel wheat gene encoding a putative chitin‐binding lectin is associated with resistance against Hessian fly

SUMMARY The gene‐for‐gene interaction triggering resistance of wheat against first‐instar Hessian fly larvae utilizes specialized defence response genes not previously identified in other interactions with pests or pathogens. We characterized the expression of Hfr‐3 , a novel gene encoding a lectin‐like protein with 68–70% identity to the wheat germ agglutinins. Within each of the four predicted chitin‐binding hevein domains, the HFR‐3 translated protein sequence contained five conserved saccharide‐binding amino acids. Quantification of Hfr‐3 mRNA levels confirmed a rapid response and gradual increase, up to 3000‐fold above the uninfested control in the incompatible interaction 3 days after egg hatch. Hfr‐3 mRNA abundance was influenced by the number of larvae per plant, suggesting that resistance is localized rather than systemic. In addition, Hfr‐3 was responsive to another sucking insect, the bird cherry‐oat aphid, but not to fall armyworm attack, wounding or exogenous application of methyl jasmonate, salicylic acid or abscisic acid. Western blot analysis demonstrated that HFR‐3 protein increased in parallel to mRNA levels in crown tissues during incompatible interactions. HFR‐3 protein was detected in both virulent and avirulent larvae, indicating ingestion. Anti‐nutritional proteins, such as lectins, may be responsible for the apparent starvation of avirulent first‐instar Hessian fly larvae during the initial few days of incompatible interactions with resistant wheat plants.