Molecular characterization of two kiss genes and their expression in rohu (Labeo rohita) during annual reproductive cycle.

Kisspeptin is an important regulator of reproduction in mammals and presumably non-mammalian species. In the Indian subcontinent, rohu (Labeo rohita) is a commercially important seasonal breeder freshwater fish species, but till date, the expression of kisspeptin gene during different phases of annual reproductive cycle has not been investigated. To address this, we cloned and characterized kiss1 and kiss2 full-length cDNA by RACE (rapid amplification of cDNA ends), and analyzed their expressions in brain-pituitary-gonad (BPG) axis by quantitative real time PCR (qRT-PCR) assay at various gonadal developmental stages of the annual reproductive cycle. Full-length rohu kiss1 and kiss2 cDNA encodes 116 and 125 amino acids respectively, and in the adult fish, they were widely expressed in brain, pituitary, gonad, liver, muscle, kidney, intestine and eye. In male, kiss1 mRNA in brain and testis showed the highest level of expression during meiosis division of the gonad. The kiss2 mRNA revealed the highest expression during recrudescence stages in the brain, spermiation stages in pituitary and post-spawning stages in testes. In females, significantly (p<0.05) a higher level of kiss1 transcript was expressed in brain and ovary, in the full grown oocyte stages, whereas during pre-vitellogenic and vitellogenic stages in pituitary. The kiss2 gene expression was almost similar at various gonadal developmental stages in the brain and ovary, but, highest expression was detected in full grown oocyte stages in the pituitary. These results together may suggest the involvement of two kiss genes in the control of seasonal gonadal development in rohu.