Do Legume Storage Proteins Play a Role in Defending Seeds against Bruchids?

Abstract

The seeds of plants are rich stores of proteins, carbohydrates, and lipids and are therefore used by heterotrophs as valuable food sources. Humans use seeds as a major food source and have learned, through agricultural practice, how to increase the levels and the quality of their components. They have also learned how to deal with the multiplicity of toxic or antinutritional compounds present in seeds. It is believed that these seeds, most of which are not essential for the establishment of the new plant following germination, contribute to the protection and defense of seeds against pathogens and predators. However, insects, fungi, and bacteria have also learned how to cope with detrimental compounds in order to take advantage of the high nutritional value of seeds.Coleopteran insects of the family Bruchidae, the seed weevils, have been associated with the seeds of leguminous plants through co-evolutionary processes. These processes have permitted the weevils to thrive on seeds full of toxic compounds, in contrast to the majority of the other potential aggressors, which are incapable of dealing with them. The association between bruchids and legume seeds is highly specific with only seeds of a very few species being attacked by any one insect species.Among our food sources, plants of the legume family contribute some of the most important protein-rich seeds. The common bean (Phaseolus vulgaris), native of the New World and the cowpea (Vigna unguiculata), which originated in Africa, are heavily attacked by bruchids, both in the field and in storage. Infestations are commonly so heavy that the seeds are unsuitable for use as food, feed, or planting.Control of bruchid infestation is done by treating stored seeds with methyl bromide, carbon disulfide, and several other chemicals. These are considered environmentally undesirable and are too expensive for subsistence farmers. To increase the insect resistance of cultivated varieties plant breeders are interested in understanding resistance mechanisms that operate in wild varieties or why certain bruchids attack one cultivated species but not another.Both the common bean and cowpea are endowed with compounds called general defensive compounds that protect their seeds against widely different herbivores. Among these are the tannins, cyanogenic glucosides, non-protein amino acids, and proteins such as protease and amylase inhibitors, lectins, chitinases, ␤-1,3-glucanases. These defensive compounds are ineffective against the host-specific bruchids, Callosobruchus maculatus and Zabrotes subfasciatus, which attack cowpea and common bean, respectively. Host-specific defenses are rare and are generally found in populations in the centers of dispersion of the particular plant species. Landraces of cowpea and common bean that produce seeds resistant to their associated bruchids have been discovered respectively in West Africa and Mexico. The biochemical basis of the resistance of cowpea and common bean seeds to C. maculatus and Z. subfasciatus, respectively, is the focus of t...

Digestive enzymes during development of Ceratitis capitata (Diptera:Tephritidae) and effects of SBTI on its digestive serine proteinase targets

“…Plant proteinase inhibitors, a-amylase inhibitors, lectins and chitin binding proteins are usually expressed in response to herbivore insects, pathogens and wounding (Ryan, 1990;Botella et al, 1996;Koiwa et al, 1997;Sales et al, 2001) and may affect development by interfering in the proteolytic processes of a wide range of potentially damaging organisms, including bacteria, fungi, nematodes (Haq et al, 2004) and insects (Terra and Ferreira, 1994;Pompermayer, et al, 2001;Falco and Silva-Filho, 2003). The effects on insects can be observed when digestive enzymes are inhibited or when defense proteins bind to the gut structures of larvae and insects (XavierFilho, 1993).…”

Biochemicals Associated With Callosobruchus Chinensis Resistance in Soybean.

“…6(5), 292-305 294 Bradford reagent were added and mixed with the samples, then left to stand for color development. Absorbance was read at 595nm and bovine serum albumin was used to prepare the standard curve to estimate the protein concentration in samples (Sales et al 2000). …”

“…Soybean genotypes did not show variations in protein concentration indicating that proteins were not responsible for resistance. Sales et al, (2000) reported that proteins such as protease, amylase inhibitors, lectins and chitinases are ineffective against host specific bruchids such as C. chinensis, C. maculatus and Zabrotes.…”

In Silico Identification of Regulatory Elements in Promoters

“…Consequently, there is a plethora of pathogens attacking plant seeds. Certain pests such as coleopteran insects of the family Bruchidae, have evolved with leguminous plants (Sales et al, 2000). It is believed that these seeds, most of which are not essential for the establishment of the new plant following germination, contribute to the protection and defense of seeds against pathogens and predators.…”

“…Our pervious study also confirmed that legumin promoter in expressed in the developing seedling as well (Jaiswal et al, 2007). Recent studies have shown that these promoters are expressed in non seed tissues as well (Zakharov et al, 2004) and play a role in bruchid (insect) resistance (Sales et al, 2000). In such a scenario where seed storage protein performs an additional task of pathogen defense its prompter must have responsive elements to such stresses.…”