Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 2
interaction with negatively charged cell walls and/or membranes, followed
by the peptide insertion and membrane permeabilization (Brogden, 2005).
This mode of action could explain why AMPs fail to induce resistance and
are highly effective against pathogenic microorganisms resistant to
conventional antibiotics (Vizioli and Salzet, 2002). The development of
resistance to AMPs appears to be rather difficult, since it implies dramatic
changes in the phospholipid composition of cell membranes that may result
in pleiotropic effects on transport and enzymatic systems, seriously
threatening microorganism survival (Alberola et al., 2004). In addition to
their capacity to permeabilize membranes, recent observations have shown
that some peptides can also be translocated to the microorganism cell
cytoplasm and interact with intracellular targets, interfering with cell wall,
nucleic acid or protein synthesis and with enzymatic activity (Brogden,
2005).
In penaeid shrimps, three main families of AMPs have been currently
described and characterized from the haemocytes: penaeidins (Destoumieux
et al., 1997), crustins (Bartlett et al., 2002) and anti-lipopolysaccharide factors
(ALFs) (Somboonwiwat et al., 2005). Penaeidins are mainly active against
gram-positive bacteria, filamentous fungi (Destoumieux et al., 1999), viruses
and protozoans (Bachere, 2003). Whereas ALFs have a broader antimicrobial
spectrum, including gram-negative bacteria (Somboonwiwat et al., 2005; de
la Vega et al., 2008). Conversely, crustins are reported to have a more-
restricted activity spectrum, affecting mainly marine gram-positive bacteria
(Relf et al., 1999; Bartlett et al., 2002; Zhang et al., 2007). In shrimps, AMPs
have been proved to be produced and stored in the haemocytes granules
(Shigenaga et al., 1990; Destoumieux et al., 2000b; Mitta et al., 2000, Lamberty
et al., 2001). AMP gene expression and distribution are regulated through
haemocyte reactions, such as cell recruitment and massive release of AMPs
and through haemocyte proliferation, which characterizes a system reaction
(Munoz et al., 2002). Transcripts of AMP-encoding genes have also been
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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