Abstract
Isolation and characterization of genes involving gonadal development are an initial step towards understanding reproductive maturation and sex determination of the giant tiger shrimp ( Penaeus monodon). In the present study, 896 clones from the testis cDNA library were sequenced. A total of 606 ESTs (67.6%) significantly matched sequences in the GenBank ( E-value < 1e− 04) whereas 290 ESTs (32.4%) were newly unidentified transcripts. The full length cDNA of genes functionally involved in testicular development including cyclophilin A ( PMCYA), small ubiquitin-like modifier 1 ( PMSUMO-1), ubiquitin conjugating enzyme E2, dynactin subunit 5, cell division cycle 2 ( cdc2) and mitotic checkpoint BUB3 were discovered. In addition, Tra-2, a gene involving sex determination cascades, was successfully characterized by RACE-PCR and first reported in crustaceans. Expression analysis indicated that a homologue of low molecular weight neurofilament protein XNF-L (termed P. monodon testis-specific transcript 1, PMTST1; N = 8 for each sex) was only expressed in testes but not ovaries. PMCYA, thyroid hormone receptor-associated protein complex 240 kDa component ( Trap240), multiple inositol polyphosphate phosphatase 2 ( MIPP2) and heat shock-related 70 kDa protein 2 ( HSP70-2), but not PMSUMO-1, PMTra-2 and prohibitin2 were differentially expressed between ovaries and testes of P. monodon. Expression of PMTST1 was up-regulated but that of the remaining genes in testes of P. monodon broodstock was down-regulated after shrimp were molted ( P < 0.05). Significant reduction of PMSUMO-1 and increment of prohibitin2 transcripts in domesticated broodstock ( P < 0.05) suggested that these reproductively related genes may be used as biomarkers to evaluate reduced degrees of the reproductive maturation in domesticated P. monodon.
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