The seed coat of Phaseolus vulgaris interferes with the development of the cowpea weevil [Callosobruchus maculatus (F. ) (Coleoptera: Bruchidae)]

We have confirmed here that the seeds of the common bean (Phaseolus vulgaris, L.) do not support development of the bruchid Callosobruchus maculatus (F.), a pest of cowpea [Vigna unguiculata (L.) Walp] seeds. Analysis of the testa (seed coat) of the bean suggested that neither thickness nor the levels of compounds such as tannic acid, tannins, or HCN are important for the resistance. On the other hand, we have found that phaseolin (vicilin-like 7S storage globulin), detected in the testa by Western blotting and N-terminal amino acid sequencing, is detrimental to the development of C. maculatus. As for the case of other previously studied legume seeds (Canavalia ensiformis and Phaseolus lunatus) we suggest that the presence of vicilin-like proteins in the testa of P. vulgaris may have had a significant role in the evolutionary adaptation of bruchids to the seeds of leguminous plants.

Cysteine proteinases and cystatins

This review describeds the definition, localization, functions and examples of cysteine proteinases and their protein inhibitors in vertebrate, non-vertebrate animals and plants. These inhibitors are related with defense mechanisms of plant against pests. It also describes the factors involved in the specific cysteine proteinase-cystatin interaction and high degree of affinity and large specificity in this interaction which are not only represented by the compatibility between amino acid residues of the active site involved in catalysis, but also of all amino acid residues that participante in the enzyme-inhibitor interaction

Alfa-amylase inhibitors of legume seeds and their involvement in the resistance to bruchid beetles

The presence of inhibitors of alfa-amylases from several sources (bacterial, plant, insect and mammallian) was investigated in seeds of several food legumes. No inhibitor of any of the tested enzymes was found in Phaseolus lunatus (Lima bean) seeds while the presence of inhibitors of insect (bruchid), porcine pancreas and human saliva alfa-amylases was confirmed in the seeds of P. vulgaris (common bean). Glycine max (soybean) seeds showed alfa-als for all the tested enzymes except for the porcine pancreatic amylase. Although we have found low levels of alfa-als in both bruchid-susceptible and resistant cowpea (Vigna unguiculata) seeds their presence does not correlate with the resistance shown by the seeds of some cultivars to the cowpea weevil Callosobruchus maculatus. The results reported here suggest that alfa-Als are not involved in the resistance of seeds of some cowpea lines to C. maculatus and that variant vicilins, the 7 S storage proteins involved in this resistance, do not show any inhibitory towards bruchi alfa-amylases