Mitochondrial DNA Dosage Effects in Triploid Grass Carp

Abstract

The grass carp Ctenopharyngodon idella is used widely in aquaculture for aquatic weed control. Historically, concern about the proliferative growth of nonnative diploid grass carp populations led to development of the hydrostatic pressure shock technique for the production of sterile triploids. Despite the success of this technique in accomplishing management goals, little is known about the cellular physiology of triploids. In particular, few studies have explored whether the induction of triploidy via hydrostatic pressure shock affects mitochondrial DNA (mtDNA) copy number in addition to that of chromosomal DNA. While the nuclear DNA (nDNA): mtDNA ratio is conserved in polyploid yeast, there are few data suggesting that vertebrate polyploids have nDNA: mtDNA ratios consistent with those of their diploid counterparts. In this study, two novel quantitative polymerase chain reaction assays were used to explore gene copy number in the nuclear and mitochondrial genome of diploid and triploid grass carp and to determine whether nuclear–mitochondrial copy number differences can be exploited to determine the ploidy of individual fish. The results of this study suggest that the ratio of mtDNA to overall cellular DNA is conserved in vertebrate polyploids and that real-time assays of mtDNA copy number are not a feasible alternative to current methodologies for identifying triploid grass carp.