The Effects of the Masou Salmon Delta5-Desaturase Transgene on N-3 Fatty Acid Production in F1 Transgenic Common Carp (Cyprinus carpio) and Channel Catfish (Ictalurus punctatus)

Abstract

The objectives of this study were determine the effectiveness of the Masou salmon delta5-desaturase transgene driven by a beta-actin promoter for improving n-3 fatty acid production in F1 transgenic common carp, Cyprinus carpio, and channel catfish, Ictalurus punctatus as well as to determine pleiotropic effects of the transgene on growth, growth variation, and survival. Another important aspect of the experiment was to determine the validity of using smaller weights of muscle for lipid extraction than traditionally utilized. F1 generation common carp and channel catfish were spawned from confirmed transgenic parents. Muscle samples were obtained from these progeny and lipid extraction was performed. Quantification of n-3 fatty acid levels was accomplished through gas chromatography-mass spectrometry. In general, n-3 fatty acid production was higher in transgenic individuals than in controls. Channel catfish showed no significant difference in n-3 fatty acid production because of low sample size, but trends towards increased production can be seen for n-3 fatty acids, in terms of total FAME percentage, α-linolenic acid (ALA) and docosahexaenoic acid (DHA), however these were not significantly different from controls (P = 0.212 and 0.207 respectively). The product on the n-6 side, arachidonic acid (AA), increased by 12.86% (P = 0.8). Precursors to n-6 delta5-desaturation, linoleic acid (LA) and dihomo-γ- linoleic acid (DGA) decreased 13.2% and 11.87% respectively (P = 0.116 and 0.8 respectively). On a mg/g weight basis for eicosapentaenoic acid (EPA) (P = 0.089), DHA (P = 0.078), total HUFA (P = 0.056) were higher in transgenic channel catfish. Fatty acid profiles for transgenic channel catfish were significantly more uniform compared to their control counter parts. Transgenic F1 common carp showed variation in lipid profile and higher level of saturated fatty acids when compared to controls. Transgenic F1 common carp showed higher variation in lipid profile and higher level of saturated fatty acids when compared to controls. Total fatty acid production of F1 desaturase common carp (9.55mg) and controls (9.93mg) per gram wet weight of muscle were not different (P = 0.68). As a percentage of FAME, desaturase F1 common carp showed a 1.14-fold decrease (P = 0.35) in n-3 fatty acid levels measured as a change in ALA, DHA, and EPA compared to controls. Individually, as a percentage of total fatty acids, ALA increased 20.72% (P = 0.18) A large number of pleiotropic effects were attributed to desaturase gene insertion. The desaturase transgene appeared to have variable results on body weight in different families of channel catfish, and observed body weights of desaturase common carp were 20.4% lower than controls. This transgene made growth rates and fatty acid profiles more uniform. Observed disease resistance was improved in transgenic channel catfish, but tolerance of low dissolved oxygen was decreased. The effects of the transgene varied between channel catfish and common carp. Desaturase transgenesis affected n-3 fatty acid production in a positive direction, showing promise for future work in this area, and when utilizing homozygous transgenic individuals in contrast to the heterozygous individuals utilized in the current study.