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maculatus
larvae that die in non-host
Canavalia ensiformis
(Oliveira et al., 1999),
Phaseolus
lunatus
(Moraes et al., 2000) and
Phaseolus vulgaris
(Silva et al., 2004) seeds does not cross
the seed coat and that vicilin-like proteins isolated from these seed coats were toxic to this
insect larvae.
Although an enormous number of toxic proteins and peptides found in seed cotyledons
have been related to the resistance of some seeds against insects (Macedo et al. 1993; Gomes
el al. 1996; Carlini et al. 1997; Carlini & Grossi-de-Sá, 2002; Moura et al. 2007), almost no
work has considered the toxicity of the seed coat as an important factor for such resistance,
despite the knowledge that this tissue is the first natural barrier encountered by pests of stored
seeds. The overall
strategy has been proposed by Miller et al. (1999), who proposes that
tissues of developing soybean seed coats may be targeted for modification of tissue
expression aiming to influence properties of mature seeds. Additionally, a large amount of
hydrophobic proteins which may prevent pathogen attachment and penetration to the seed
coat and act as deterrent or toxin to other organisms, such as insects, have been located at the
special adherence sites formed by the merging of pod wall tissues and soybean seed coats.
Considering this aspect, Gijdzen et al. (1999b) suggested that it may be possible to alter seed
coat characteristics through manipulation of gene expression in the ovary wall. Although
seeds have been the subject of extensive studies for many years, their seed coats are just
beginning to be examined from the perspective of biochemistry, molecular genetics and
control of development. Within the seed coat are a number of unique tissues that undergo
differentiation to serve specific functions in the seed. A large number of genes are known to
be specifically expressed within the seed coat tissues; however, very few of them are
understood functionally. The seed coat synthesizes a wide range of novel compounds that
may serve the plant in diverse ways, including defense and control of development. The use
of seed coat biotechnology to enhance seed quality and yield or to generate novel components
has not been exploited, largely because of lack of knowledge of the genetic systems that
govern seed coat development and composition as well as the function of these compounds
(Moïse et al. 2005).
In the work presented here, we summarize some of the results obtained by our research
group when studying the specific relationship among the soybean seed and the bruchid
C.
maculatus
, with major emphasis on the influence of the soybean seed coat tissue upon the
disruption of seed infestation by the insect.
M
ATERIAL AND
M
ETHODS
Seeds
Commercial soybean (
Glycine max)
and cowpea
(
Vigna unguiculata
cv. Fradinho) seeds
were bought from local markets at Campos dos Goytacazes, RJ, Brazil.
Non-commercial soybean cultivars (cv.) - Conquista, UFV-20 Florestal, UFUS 2003,
UFUS 2005, Tucunaré and Elite - were obtained from the Departamento de Fitotecnia of the
Universidade Federal de Viçosa (UFV), Viçosa-MG, Brazil.
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