Single nucleotide polymorphisms of fad2 gene from tung tree, Vernicia fordii, a potential biodiesel plant

Tung tree, Vernicia fordii, is an oil-producing plant with multiple uses, especially with its great potential in biodiesel production. Single nucleotide polymorphism (SNP) providing an abundant source of DNA polymorphisms, is essential for developing new cultivars with high yield, good quality, and wide adaptation. However, there are a few reports about the DNA sequence variation in tung tree, especially about the key genes involved in lipid biosynthesis. In the present study, a 1.2-kb coding region of fad2 gene, encoding oleate desaturase, was investigated by sequencing a sample population of 38 nationwide V. fordii accessions. Two SNPs were detected, giving an average SNP frequency of 1/576 bases and average nucleotide diversity of 0.00041 (θw). Although the number of SNPs is small, the two SNPs resulted in changed amino acids. Further analysis of the fatty acid (FA) compositions for the mutant accessions suggested that both of the two SNPs in the fad2 coding region were likely to increase levels of polyunsaturated FAs, especially the content of eleostearic. The fad2 gene is very important and conservative among many plant species, and also among diverse tung tree germplasm accessions. Nonsynonymous mutations could occur in the coding region of this gene, even though the rate is low in tung tree. This characterization of the fad2 gene from tung tree and its possible effect on lipid metabolism should provide new insights into the regulation of seed lipid metabolism. It is feasible to manipulate seed oil composition of tung tree using genetic and genomic approaches for a variety of applications in industry and energy.