ABSTRACT: 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 α-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.
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a DNA Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Kasetsart University, Kamphaengsaen Campus, Nakorn Pathom 73140, Thailand.
b Marine Science Department, Fisheries Faculty, Kasetsart University, Bangkok 10900, Thailand.
c Rice Genes Discovery Unit, National Center for Genetic Engineering and Biotechnology, Kasetsart University, Kamphaengsaen Campus, Nakorn Pathom 73140, Thailand.
* Corresponding author, E-mail: suwit@dnatec.kps.ku.ac.th, suwitwuth@hotmail.com
Received 17 May 2004,
Accepted 25 Feb 2005
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