SBBq
XL Annual Meeting of Brazilian Biochemistry and Molecular Biology Society
th
rd
Foz do Iguaçu, PR, Brazil, April 30 to May 3 , 2011
Vicilins: Plant Defense Proteins
Uchôa, A.F.1; Oliveira, A.S.2; Amorim, T.M.L.2; Morais, A.H.A2
and Santos, E.A2.
1
Departamento de Biologia Celular e Genética, 2Departamento de Bioquímica,
Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, RN.
Plants have developed a variety of chemical and physical defense strategies to
protect themselves against pests and pathogens. The defense arsenal is
composed of secondary metabolic compounds, such as alkaloids, terpenes,
phenolic compounds, cyanogenic glycosides, and proteins. Lectins, chitinases,
digestive enzyme inhibitors, ribosome inactivating proteins, and pathogenesis
related proteins are examples of plant defensive proteins. Biochemical studies
showed that variant vicilins (7S storage proteins) from cowpea (Vigna unguiculata
L. (Fabaceae), seeds are also defensive proteins. It was shown that ingestion of
vicilins from legume seeds were able to bind to the surface of the cowpea weevil
(Callosobruchus maculatus) larval midgut and to the peritrophic matrices of the
midguts of sugar cane stalk borer (Diatraea saccharalis), yellow meal worm
(Tenebrio molitor), Mediterranean fruit fly (Ceratitis capitata) and Plodia
interpunctella, inhibiting larval development. It has been suggested that binding of
proteins to the chitin-containing membranes in insects could interfere with the guts
functions, which are indispensable for survival. Results demonstrated binding of
vicilins to brush border membrane, suggesting the existence of specific receptors.
Vicilins also were detected in the haemolymph and in internal organs, such as fat
body and malpighian tubules from C. maculatus. Vicilins were also shown to inhibit
Fusarium oxysporum, Colletotrichum musae, and Saccharomyces cerevisiae fungi
and bind to yeast cells through the association with chitin-structures. The
mechanism of action of the vicilins is not yet understood, but seems to be related
to their chitin-binding property, their low digestibility by insect proteinases and
accumulation in the fat body of larvae.
Key words: chitin-binding proteins, bioinsecticide, peritrophic membrane.
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