Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 2
20%, of all the sequences isolated in the shrimp species L. vannamei and L.
setiferus, respectively. Finally, as shown by biochemical approach, the
penaeidin-3 subgroup is dramatically the most abundantly produced
(Destoumieux et al., 1997). It represents more than 90% of all the penaeidin
mRNA sequences detected in both shrimp species (Cuthbertson et al., 2002).
2.1.3.3. Biological properties of penaeidins
Penaeidin anti-bacterial activity is predominantly directed against
gram-positive bacteria via a strain-specific inhibition mechanism and
through multiple modes of action. Penaeidins display weak anti-bacterial
activity in vitro against gram-negative strains including Vibrionaceae
species. The C-terminal domain of penaeidins presents some similarities and
partial conservation of a primary sequence motif common to several chitin-
binding proteins isolated from plants (Raikhel et al., 1993). The penaeidin C-
terminal domain was shown to confer to the whole molecule an ability to
attach chitin tightly (Destoumieux et al., 2000b). Chitin-binding ability is
most often related to an anti-fungal activity (Cuthbertson et al., 2006).
Penaeidins have broad-spectrum fungicidal activity against
filamentous fungi but are found to be inactive against yeast such as S.
cerevisiae or Candida albicans (Destoumieux et al., 1999). Interestingly,
penaeidins are active against the shrimp pathogen Fusarium oxysporum,
which is responsible for infections in different Penaeid shrimps
(Rhoobunjongde et al., 1991). Many phytopathogenic fungal strains such as
Nectria haematococca, Alternaria brassicola, Neurospora crassa and Botritys cinerea
were shown to be sensitive to the peptides, indicating that penaeidins could
have applications in agronomy as therapeutic agents. Penaeidin fungicidal
activity against the different strains was shown to be associated with
inhibition of spore germination. At lower concentrations, the peptides cause
growth inhibition of fungal hyphae, resulting in morphological
abnormalities.
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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