A normalized cDNA library from spleen of Indian catfish, Clarias batrachus, was constructed with a
redundancy factor of 2.29. A total of 2045 clones from the library were single-pass sequenced, which
generated 1937 high quality ESTs with an average read length of approximately 700 bp. Based on sequence
similarities, 65 ESTs were found to be associated with immune functions, which were mainly associated with
response to stress, response to chemical stimulus, cellular response to stimulus, response to external
stimulus, immune response and regulation of response to stimulus. The immune-relevant gene for CD141,
thrombomodulin, has been identified in Teleosts for the first time. Six EST-SSRs and three SNPs were found
associated with eight immune-relevant genes. These markers associated with important immune genes
would be useful for the identification of trait associated alleles for marker-assisted selection. The
identification of the putative immune-related genes provides a meaningful framework to understand the
Indian catfish immune system and defense mechanisms.
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