Characteristics Of Molecular Evolution For Major Cold-adapted Proteins And Enzymes In Schizopygopsis Pylzovi And Their Ecological Significance

Seasonal cold is one of the most important ecological factors restrictingplateau animals. The native plateau animals have developed their ownmechanisms in adaptation to harsh environmental stress during their longevolutional history. Schizopygopisis pylzovi is a representative species ofschizothoracine fishes widely distributed in the upper reaches of the Yellow River,affiliated lakes of the Yellow River and Qiadam drainage system, which playssignificant roles in the trophic web of plateau freshwater communities andexhibits strong adaptation to seasonal cold environment of the Qinghai-TibetanPlateau. In the present study, the full-length cDNA of ob and CS genes and thecomplete sequences of CO I, CO II and CO III genes for Schizopygopisis pylzoviwas cloned with RT-PCR,5’RACE and3’RACE methods, and the sequencefeature was analyzed. Meanwhile, the expression patterns of ob, CS, CO I, CO IIand CO III genes in tissues were detected by RT-PCR. The raletive expressionlevels of the ob, CS, CO I, CO II and CO III genes in hepatopancreas and whitemuscle for Schizopygopisis pylzovi from habitats with different temperatures weredetermined by Real-Time PCR methods. The aims for this study is to providescientific data for the adaptive mechanism of Schizopygopsis pylzovi to seasonalcold environment of the Qinghai-Tibetan Plateau. The results as follows:(1) The full-length ob cDNA sequence Schizopygopsis pylzovi was1337bp,including110bp of5′-untranslated region (5′-UTR),714bp of3′-untranslatedregion (3′-UTR) and a516bp open reading frame (ORF), which encoding170amino acids. The N-terminal of the deduced amino acid sequence had a signalpeptide sequence composed of20amino acids. The ob gene was expressed in allthe examined tissues, including heart, kidney, fat, intestine, spermary,hepatopancreas, gill, brain and muscle, while strongly expressed in heart and weakly expressed in kidney, muscle, brain, fat, intestine, gill, spermary,the lowestexpression is in hepatopancreas. The ob gene expression in the hepatopancreasand white muscle of Schizopygopsis pylzovi increased along with increase of theenvironmental temperature. On the contary, the ob gene expression wassuppressed by low temperature.(2) The full-length CS cDNA sequence Schizopygopsis pylzovi was3186bp,including142bp of5′-UTR,1637bp of3′-UTR and a1407bp open readingframe (ORF), which encoding468amino acids. The N-terminal of the encodingprotein was detected a mitochondrial transit peptide containing28amino acids,while the C-termial had a citrate synthesis signal, which motif was the amino acidsequences of346GYGHAVLRKTDPR358. The CS gene was expressed in all theexamined tissues, while strongly expressed in stomach, ovary, spermary, andexpressed relatively strong in kidney, red muscle, intestine, white musclehepatopancreas and fat, weakly expressed in heart. The CS gene expression in thehepatopancreas and white muscle of Schizopygopsis pylzovi showed the trend ofincrease along with the environmental temperature increased.(3) The complete sequence of CO I was1551bp, which composed the openreading frame encoding516amino acid residues; the CO II was691bp andcontained a690-nucleotide ORF encoding230amino acid residues; and the COIII was786bp, which composed the ORF encoding261amino acid residues. Thesemi-quantitative RT-PCR showed that CO I was expressed in all the examinedtissues, while weakly expressed in white muscle, ovary and heart, and the weakestis spermary; CO II was expressed in all the examined tissues, while strongly andsteadily expressed in the other tissues, but the weakest expression is in spermaryand fat; CO III was strongly expressed in all the examined tissues, the weakestexpression is in spermary. The expression level of CO I, CO II and CO III genesin the hepatopancreas and white muscle of Schizopygopsis pylzovi significantly increased along with increase of the environmental temperature.