A tobacco microsomal ω-3 fatty acid desaturase gene increases the linolenic acid content in transgenic sweet potato (Ipomoea batatas)

A tobacco microsomal omega -3 fatty acid desaturase gene (NtFAD3) under the control of the CaMV 35S promoter or an improved CaMV 35S promoter (E12 Omega) was introduced into sweet potato. Transformed sweet potato plants were obtained from embryogenic calli following Agrobacterium tumefaciens-mediated transformation. The transgenic plants grew normally to form storage roots and showed properties similar to those of the non-transgenic plants. The fatty acid composition in the transgenic line with a NtFAD3 gene driven by the CaMV 35S promoter was similar to that in the non-transformant. However, in the transgenic line that had a NtFAD3 gene driven by the E12 Omega promoter, linoleic acid (18:2) and linolenic acid (18:3) contents were 47.7 mol% and 24.8 mol%, respectively, which were significantly different from the 53.6 mol% and 11.3 mol%, respectively, in the non-transformant. The NtFAD3 gene driven by the E12 Omega promoter was expressed more strongly than that driven by the CaMV 35S promoter, thereby increasing the linolenic acid content in the transgenic sweet potato plants.