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Resistance to Bacillus thuringiensis Cry1Ac toxin in three strains of Heliothis virescens : Proteolytic and SEM study of the larval midgut
Author(s) -
Forcada Carmen,
Alcácer Encarna,
Garcerá Ma Dolores,
Tato Agustín,
Martínez Rafael
Publication year - 1999
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/(sici)1520-6327(199909)42:1<51::aid-arch6>3.0.co;2-6
Subject(s) - midgut , bacillus thuringiensis , heliothis virescens , cry1ac , biology , strain (injury) , microbiology and biotechnology , proteolytic enzymes , lepidoptera genitalia , toxin , larva , insect , noctuidae , botany , bacteria , biochemistry , genetically modified crops , transgene , anatomy , gene , enzyme , genetics
In a previous study, we demonstrated that resistance to Bacillus thuringiensis toxins in Heliothis virescens might be related to differences in the composition of the proteolytic extracts from insect midgut. There, we found specific proteolytic bands present in the gut extracts of the resistant strain and absent from the susceptible one. Here we report related facts using a new resistant strain (KCB) and a cross between the two strains used in our previous study. As would be expected, no quantitative differences in total proteolytic activity were found between the strains, although qualitative differences related to the presence or absence of specific proteolytic activity bands using SDS‐PAGE could be responsible for the observed resistance phenomenon. Moreover, an SEM study made at different time intervals after intoxication shows that in the initial hours following intoxication, both the susceptible and the resistant strains show significant damage to the midgut epithelium. In the interval between 3 and 48 h, however, the resistant strain recovered such that by 48 h it had fully recovered whereas the susceptible strain did not. Arch. Insect Biochem. Physiol. 42:51–63, 1999. © 1999 Wiley‐Liss, Inc.