Induction of Elastase in a Zoophytophagous Heteropteran, Lygus hesperus (Hemiptera: Miridae)

Abstract

One potential biochemical adaptation to mixed feeding habits, or zoophytophagy, is enzyme induction/enzyme repression. We investigated the potential of the highly polyphagous mirid Lygus hesperus Knight to increase its production of the specialized proteolytic enzyme, elastase (E. C. 3. 4. 31.36). Efforts to induce elastase production were made by feeding L. hesperus on an artificial diet spiked with elastin. Short-term (less than one generation) and long-term (three generations) tests were conducted to determine the effect of acute versus chronic exposure to elastin, a protein that may be present in extra cellular matrix of prey. Elastase activity was much greater in the salivary gland complex (SGC) of individuals fed elastin-containing diet than it was in those fed the control diet. The elevated elastase activity in the elastin treatment group indicated the inducibility of this proteolytic enzyme, especially in the SGC. The results also indicated that the SGC, rather than the gut, is the principal site of elastase production.