Mitochondria And Infertility In An Improved Triploid Crucian Carp

Mitochondrion is the power house of the eukaryotic cell and plays an essential role in energy metabolism and programmed cell death. Mitochondrion has attracted considerable attention, because of it has its own genome(mtDNA). An improved triploid crucian carp(ITCC), with three sets of chromosomes, can’t complete the chromosomal pairing properly during meiosis. Hence, ITCC is unable to produce normal mature gametes. In addition, the experiment of cultivation in ten years also proved that ITCC is sterile.By taking advantage of these special objects: the infertile ITCC and fertile allotetraploid(4nAT), improved red crucian carp(IRCC), autotriploid, this study was aimed to explore the possible role of mtDNA in fish polyploidy and fertility, and furthermore explored the reason that caused those changes. In terms of microstructure, the two types gonads(testis, ovary type) of ITCC were compared with normal gonad of 4nAT based on the method of paraffin section. From the aspect of molecular biology, mtDNA and tfam mRNA were quantified in each gonad sample(ITCC, 4nAT, IRCC) by using real-time quantitative PCR. On the other hand, the mtDNA/β-actin gene ratio in the heart, liver, kidney and ovary of ITCC and autotriploid were also determined. The results show that the mtDNA content in the ovary is significantly higher than one’s in testis of 4nAT and IRCC, with the ovarian mtDNA being higher in 4nAT than in IRCC; Interestingly, the ovarian mtDNA of ITCC not only significantly lower than its testis, but also lower than other ovaries of fertile fish. The high levels expression of TFAM is an important factor for causing mtDNA content differences; For another thing, it was found that the mt DNA content exhibited some patterns of organ variations in heart, liver and kidney of ITCC and autotriploid. Taken together, these results suggest a correlation between the gonadal mtDNA content and fertility in ITCC and verified the theory that the mtDNA content in gonad of infertile individual is corresponding higher or lower than normal range in a corollary manner.