PUFAs in daily diet are needed. N-6 PUFAs, such as
LA, can be converted into n-3 PUFAs by n-3 fatty acid
desaturases (FAD3) (Oura and Kajiwara 2004). As
humans neither do other vertebrate animals including
cattle do not produce FAD3, an alternative approach is
needed to increase n-3 PUFAs contents in the products
from livestock animals.
Transgenic technology has been applied to generate
new high value-added livestock animals to meet the
growing demand for healthy food. So far, FAD3
derived from spinach, Caenorhabditis elegans (C.
elegans) and Caenorhabditis briggsae (C. briggsae)
have been heterologously expressed in pigs (Zhou et al.
2014; Pan et al. 2010; Lai et al. 2006; Saeki et al. 2004),
dairy cattle (Wu et al. 2012) and sheep (Zhang et al.
2013). C. elegans fat1 gene, which encodes FAD3, is a
good candidate gene to breed into new transgenic
animals to increase the contents of n-3 PUFAs. To the
best of our knowledge, no fat1 transgenic beef cattle
have been obtained up to now. Therefore, in this study,
mfat1 (codon-optimized C. elegans fat1 gene) transgenic
beef cattle were first generated via somatic cell
nuclear transfer (SCNT). A plasmid containing the
codon-optimized C. elegans mfat1 gene was constructed
and transfected into the primary fetal fibroblasts
from Luxi Yellow cattle. Luxi Yellow is a well-known
Chinese breed of indigenous cattle, with a high beef
yield. The obtained mfat1 transgenic Luxi cattle
heterologously expressed FAD3, and showed significantly
increased contents of n-3 PUFAs in muscle
tissue. Also, the ratio of n-6/n-3 PUFAs in transgenic
cattle was 0.95: 1, which was lower than that 5.33: 1 of
transgenic negative cattle. Our results demonstrate that
the mfat1 gene from C. elegans could be functionally
expressed in beef cattle and will decrease the ratio of
n-6/n-3 PUFAs in muscle tissue, which may make beef
a good source of n-3 PUFAs in human daily diet.