Interestingly, several unknown genes have been found to be
highly altered in expression levels in response to stress/pathogen
induction. Clearly, the function of these unknown gene products
needs to be further investigated. Although EST and microarray
analysis are limited, as, for example, important immune mediators
that do not alter significantly in transcript expression levels but are
post-translationally modified or are involved in the early parts of
signal cascades and at low expression levels, these approaches
cover most of the current knowledge of shrimp immunity while the
whole genome analysis remains unavailable. However, to compliment
these approaches, proteomic approaches are being employed
as well as, but both are restricted by the absence of good transformation
vectors and permanent cell lines, in contrast to insects,
confining the subsequent analysis to the use of transient gene
knockdown and heterologous gene expression studies and the use
of yeast two-hybrid systems (see next section).