cDNA cloning of blue gourami (Trichogaster trichopterus) prolactin and its expression during the gonadal cycles of males and females.

BACKGROUND

The blue gourami fish (Trichogaster trichopterus) provides a unique model for the study of reproduction endocrinology in teleost fish. Its oocyte development may be controlled easily, and the vitellogenic and final maturation phases may be separated artificially in the laboratory. Moreover, this gourami exhibits exclusive parental behavior.

AIM

The aim of the present study was to clone and sequence the blue gourami PRL (bgPRL) cDNA in order to enable the determination of its mRNA levels in the male and female blue gourami during the gonadal cycles.

MATERIALS AND METHODS

bgPRL was cloned by extracting total RNA from freshly excised pituitaries of gourami fish, followed by cDNA synthesis, rapid amplification of cDNA ends (RACE)-PCR and finally, sequencing. bgPRL mRNA expression was determined by realtime PCR, and results were normalized with 18S RNA.

RESULTS

When bgPRL was compared to PRLs of other fish, it had the most homology with PRL of Perciformes and the least with those of Anguilliformes. bgPRL was expressed during the entire gonadal cycle in males and females. The average levels of PRL mRNA in juvenile and low vitellogenetic females were lower than in mature females (at high vitellogenesis and maturation), but the differences were not significant. On the other hand, the PRL mRNA levels in mature reproductive males (nestbuilders) and non-reproductive (non-nest-builders) were significantly higher in comparison to young males.

CONCLUSIONS

The results of this study imply that PRL has a possible role in the endocrine control of gonadal development in fish, in addition to its role in reproductive behavior.