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Insecticidal Action of Bauhinia monandra leaf lectin (BmoLL) against Anagasta kuehniella (Lepidoptera: Pyralidae), Zabrotes subfasciatus and Callosobruchus maculatus (Coleoptera: Bruchidae)
Maria Lígia Rodrigues Macedo1, Maria das Graças Machado Freire2, Desiree Soares da Silva1, Maria Barbosa Reis da Silva 3, Luana Cassandra Breitenbach Barroso Coelho 3
1Depto de Ciências Naturais,UFMS,
Três Lagoas-MS (bioplant@terra.com.br), 2Institutos Superiores de
Ensino do CENSA; Campos de Goytacazes, RJ. 3Departamento de
Bioquímica, Universidade Federal de Pernambuco, Recife, PE
Bruchid larvae cause major losses in grain legume crops throughout the world. The
mediterranean flour moth is of major economic importance as a flour and
grain feeder; it is often a severe pest in flour mills.Plant lectins have been implicated as antibiosis factors against insects. Bauhinia monandra leaf lectin (BmoLL) was tested for anti-insect activity against Callosobruchus maculatus, Zabrotes subfasciatus and Anagasta kuehniella larvae. To examine the effects of BmoLL on C. maculatus and Z. subfasciatus larval development and the effects on A. kuehniella, the artificial seed systems used were previously developed by Macedo et al. (2003).
Proteinases were obtained from the midguts of fourth-instar larvae.
Midgut tissue homogenates were centrifuged at 15,000 g for 15 min at
5ºC and the supernatants were used as enzyme sources.To examine the protein effects on different insects, larvae up to the fourth instar were fed an artificial diet-containing BmoLL at concentration of 0-1% (w/w).
The susceptibility of BmoLL to the action of trypsin, of the mixture of
pepsin and papain (1:1), of the basic proteolytic enzymes in A. kuehniella midgut and to acid proteolytic enzymes in Z. subfasciatus and C. maculatus midgut were assayed by incubating these enzymes with the protein followed by SDS-PAGE. BmoLL produced ca. 50% mortality to Z. subfaciatus and C. maculatus when incorporated in an artificial diet at a level of 0.5% and 0.3% (w/w), respectively. BmoLL up to 1% did not significantly decrease the survival of A. kuehniella larvae, but produced a decrease of 40% weight. Affinity chromatography showed that BmoLL bound to midgut proteins of the insect C. maculatus. 33-subunit BmoLL was not digested by midgut preparations of these bruchids. BmoLL-fed C. maculatus larvae increased the digestion of potato starch in 25% when compared with the control. The
transformation of the genes coding for this lectin could be useful in
the development of insect resistance in important agricultural crops.
Supported by: FINEP, CNPq, FUNDECT.
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