Effects of Manduca sexta allatostatin and an analogue on the peach-potato aphid Myzus persicae (hemiptera: aphididae) and degradation by enzymes in the aphid gut
✍ Scribed by H. June Matthews; Rachel E. Down; Neil Audsley
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 192 KB
- Volume
- 75
- Category
- Article
- ISSN
- 0739-4462
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✦ Synopsis
Abstract
The oral toxicity of the C‐type allatostatin, Manduca sexta allatostatin (Manse‐AS) and the analogue δR^3^δR^5^Manse‐AS, where R residues were replaced by their D‐isomers, were tested against the peach‐potato aphid Myzus persicae by incorporation into an artificial diet. Both peptides had significant dose‐dependent effects on mortality, growth, and fecundity compared with control insects. The analogue, δR^3^δR^5^Manse‐AS, had an estimated LC~50~ of 0.31 µg/µl diet and was more potent than Manse‐AS (estimated LC~50~ of 0.58 µg/µl diet). At a dose of 0.35 µg δR^3^δR^5^Manse‐AS/µl diet, 76% of the aphids were dead after 6 days and all were dead after 10 days. In comparison, three times the dose of Manse‐AS was required to achieve 74% mortality after 8 days and 98% mortality after 16 days. The degradation of both peptides by extracts prepared from the gut of M. persicae was investigated. The estimated half‐life of Manse‐AS, when incubated with the gut extract from M. persicae, was 31 min. Degradation was due to a cathepsin L‐like cysteine protease, carboxypeptidase‐like activity, endoprotease activity with glutamine specificity, pyroglutamate aminopeptidase activity, and possibly trypsin‐like proteases. The half‐life of the δR^3^δR^5^ Manse‐AS analogue was enhanced (73 min) with the D‐isomers of R appearing to prevent cleavage around the R residues by cathepsin L‐like cysteine proteases or from trypsin‐like proteases. The greater stability of the analogue may explain its increased potency in M. persicae. This work demonstrates the potential use of Manse‐AS and analogues, with greater resistance to enzymatic attack, in aphid control strategies. © 2010 Wiley Periodicals, Inc.