Chitin is only a minor component of the peritrophic matrix from larvae of Lucilia cuprina.
The gut of most insects is lined with a peritrophic matrix that facilitates the digestive process and protects insects from invasion by micro-organisms and parasites. It is widely accepted that the matrix is composed of chitin, proteins and proteoglycans. Here we critically re-examine the chitin content of the typical type 2 peritrophic matrix from the larvae of the fly Lucilia cuprina using a range of techniques. Many of the histochemical and biochemical techniques indicate the presence of chitin, although they are often adversely influenced by the presence of highly glycosylated proteins, a principal component of the matrix. The alkali-stable fraction, which is used as an indicator of the maximum chitin content in a biological sample, is only 7.2% of the weight of the matrix. Larvae fed on the potent chitin synthase inhibitor polyoxin D or the chitin-binding agent Calcofluor White, showed strong concentration-dependent inhibition of larval weight and survival but no discernible effects on the matrix structure. A bacterial endochitinase fed to larvae had no effect on larval growth and no observable effect in vitro on the structure of isolated peritrophic matrix. RT-PCR did not detect a chitin synthase mRNA in cardia, the tissue from which PM originates. It is concluded that chitin is a minor structural component of the type 2 peritrophic matrix of this insect.
Tellam
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RL
CSIRO Tropical Agriculture, Private Mail Bag 3, 4068 Queensland, Indooroopilly, Australia. ross.tellam@tag.csiro.au
Eisemann
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C
D000818:Animals; D001557:Benzenesulfonates / Q000378:metabolism; D002686:Chitin / Q000031:analogs & derivatives / Q000378:metabolism*; D002687:Chitin Synthase / Q000378:metabolism; D002688:Chitinases / Q000378:metabolism; D048271:Chitosan; D004064:Digestive System / Q000378:metabolism; D004175:Diptera / Q000378:metabolism*; D007814:Larva; D011741:Pyrimidine Nucleosides / Q000378:metabolism; D014909:Wheat Germ Agglutinins / Q000378:metabolism
D001557:Benzenesulfonates; D011741:Pyrimidine Nucleosides; D014909:Wheat Germ Agglutinins; D002686:Chitin; C007061:C.I. Fluorescent Brightening Agent 28; D048271:Chitosan; C002458:polyoxorim; D002687:Chitin Synthase; D002688:Chitinases