EST-based identification of genes expressed in the branchiae of black tiger shrimp (Penaeus monodon Fabricius)
Wuthisuthimethavee, S.; Lumubol, P.; Vanavichit, A.; Tragoonrung, S.
ScienceAsia 31(2): 137-144
Expressed sequence tag (EST) analysis is a powerful tool for gene discovery. A preliminary study of genes expressed in branchiae of Penaeus monodon comprised constructing a cDNA library, cDNA sequencing and a homology search of public databases. The constructed cDNA library contained insert sizes ranging from 0.5-1.6 kb. From 200 randomly selected EST clones, 176 (88%) were successfully sequenced and gave average read-length after vector clipping of 325 bp. A total of 26 contigs were formed after clustering the 176 ESTs. The contigs contained a total of 72 EST sequences and 104 sequences remained as singleton ESTs. Bioinformatics analysis revealed that 42 from 104 transcripts matched known genes. These were categorized into 6 classes of genes involved in gene/protein expression (50%), metabolism (23.8%), cell/organism defense (9.6%), cell structure/motility (7.1%), and cell signaling and communication (2.4%). Genes lacking enough information to be classified constituted the remaining 7.1%. This study also found a transcript with high homology to an Na+/K+-ATPase gene reported to be involved in osmoregulation of crustaceans, and especially to the [alpha]-subunit Na+/K+-ATPase in H. americanus. Expression of this gene in branchiae of low salinity-stressed P. monodon was examined using RT-PCR analysis. The results showed that the mRNA abundance in stressed shrimps decreased over 7 days in contrast to a previously- described increase in the enzyme activity.