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Serratia entomophila inoculation causes a defect in exocytosis in Costelytra zealandica larvae
Author(s) -
Gatehouse H. S.,
Marshall S. D. G.,
Simpson R. M.,
Gatehouse L. N.,
Jackson T. A.,
Christeller J. T.
Publication year - 2008
Publication title -
insect molecular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.955
H-Index - 93
eISSN - 1365-2583
pISSN - 0962-1075
DOI - 10.1111/j.1365-2583.2008.00807.x
Subject(s) - midgut , biology , actin , secretion , cytoskeleton , microbiology and biotechnology , exocytosis , biochemistry , cell , botany , larva
Rapid elimination of midgut luminal proteinase activity and gut clearance are the two major symptoms of amber disease in Costelytra zealandica larvae because of the three‐subunit protein toxin complex produced in Serratia entomophila and Serratia proteamaculans . Quantitative PCR analysis of mRNA from the major serine proteinase gene families showed that loss of proteinase activity did not result from transcriptional downregulation. Unexpectedly, protein levels and rates of protein synthesis increased, rather than decreased, in the midgut of diseased insects. Proteomic analysis of midgut tissues showed marked differences between healthy and diseased midguts. Large increases in soluble forms of both actin and tubulin were identified from 2D‐gels, together with concurrent decreases in the levels of polymeric actin‐associated proteins: actin depolymerizing factor and cyclophilin. These results suggest that the Serratia toxin acts to cause degradation of the cytoskeletal network and prevent secretion of midgut gut digestive proteinases as both the actin cytoskeleton and microtubules are involved in exocytosis. Proteinases synthesized in the diseased midgut must be rapidly degraded because they do not accumulate in an inactive form.