Abstract:
Neurotransmitters are involved in many physiological regulations in crustaceans
as well as in mammals. The black tiger prawn (Penaeus monodon) is an economically
important animal in Thailand and South East Asian countries. Therefore, the study of
their neurotransmitter receptors will lead to an understanding of their physiological
mechanisms and can be used to improve prawn production in the future. Octopamine
and tyramine are neurotransmitters that are involved in many physiological aspects
such as ovarian muscle contraction and learning behavior. The purposes of this study
were to clone neurotransmitter receptors from black tiger prawns and to analyze their
tissue distribution profiles. In this study, total RNA from brain and thoracic ganglia of
P. monodon was isolated and used to perform reverse transcription. The first strand
cDNA was used to perform PCR with degenerate primers in the conserved sequences
of the third and the seventh transmembrane domains of G-protein coupled receptors.
A PCR product of about 850-bp was sequenced. Two variants, 53 and 60 variants,
were obtained. These sequences were used to design primers to determine 3/ and 5/
ends. Amplification of the 3/ end was determined by 3/ Rapid Amplification of cDNA
Ends (3/ RACE). Two PCR products with different sizes, L-3RACE and S-3RACE,
were obtained. In addition, 5/ end was amplified from a black tiger prawns DraI
Genome WalkerTM library. One 800-bp 5/ end product was obtained. DNA
amplification of the full-length gene was performed in genomic DNA. The full-length
fragment, Pm-OA/TyrR-53 contained the sequences corresponding to the 5/ end
product, 53-variant middle sequence and L-3RACE. Its longest open reading frame
was 1329 nucleotides coding for 443 amino acids. In addition, the partial sequence,
Part-Pm-OA/TyrR-60, had sequences corresponding to the 60-variant middle
sequence and S-3RACE. The 5/ end of this gene could not be cloned. Its coding
region was 894 nucleotides coding for 298 amino acids. They reveal the sequence
similarity to octopamine/tyramine receptor negatively coupled to adenylate cyclase. In
female wild broodstock prawns, the expressions of both 53 and 60 variants were
detected in brain and thoracic ganglia and heart. Only the 53 variant was detected in
ovaries whereas only the 60 variant was detected in the abdominal muscle, suggesting
that both variants may be involved in different physiological regulation and may have
different functions in various tissues of P. monodon