Expressed sequence tags have been generated from cDNA libraries constructed from liver and
muscle tissues of female walking catfish. Two thousand and twenty-nine randomly picked cDNA clones, 991
from the liver library and 1,038 from the muscle library were sequenced. A total of 1,334 EST clones showed
significant sequence similarity to known genes in the databases, representing 303 genes from the liver library
and 234 genes from the muscle library. Fifty-one full-length genes and 95 microsatellite repeat sequences
were identified in both libraries. The majority of walking catfish EST sequences matched sequences identified
from other Siluriformes, particularly channel catfish (513 EST clones, 38.5%) and zebrafish (284 EST clones,
21.3%). A number of identified genes appeared to be expressed in specific tissues. Vitellogenins were the
most highly expressed genes in the liver of female walking catfish. Further, genes responsible for innate
immune function of fish were found only in the liver. In contrast, genes encoding structural proteins were
restricted to the muscle library. Analysis of the cDNA libraries indicates that EST approaches can provide
effective ways to characterize expressed genes in walking catfish, and these libraries would be useful resources
for identification of EST and microsatellite markers for mapping purposes.