Identification and analysis of the jnk1 gene in polyploid hybrids of red crucian carp (Carassius auratus red var.) and common carp (Cyprinus carpio L.)

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c-Jun N-terminal kinase (JNK) is an important member of the mitogen-activated protein kinase superfamily. The allotetraploid crucian carp is a product of distant hybridization of female red crucian carp with male common carp. It is the first natural case of an allotetraploid with stable genetic characters, including fertility of both female and male animals. In this study, 2 jnk1 cDNAs (including jnk1a and jnk1b) have been cloned from the polyploid crucian carp system, consisting of the allotetraploid crucian carp, the triploid crucian carp, and their original parents (red crucian and common carp). We show that jnk1a and jnk1b represent 2 splice forms arising from the jnk1 gene. On the basis of the genetic structure of jnk1a gene in the polyploid crucian carp system, we demonstrated that the allotetraploid crucian carp is phylogenetically closer to its paternal parent (common carp) than to its maternal parent. We further show a similarity between the triploid crucian carp and its original female parent (red crucian carp). Comparisons of genetic structures indicated that the jnk1b genes of allotetraploid and triploid crucian carp are more similar to those of the original paternal parent rather than the original female parent (red crucian carp). RT-PCR analysis indicated that both the jnk1a and jnk1b genes are widely expressed in fish embryos and in the adult organs, displaying distinct features of embryonic-stage and organ specificity in the polyploid crucian carp system.