Co-integration, co-expression and co-segregation of an unlinked selectable marker gene and NtFAD3 gene in transgenic rice plants produced by particle bombardment.

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Abstract
Using the scutellar tissue of rice mature embryos as a target tissue, a selectable marker gene, bar, and an unselectable gene, fatty acid desaturase gene from tobacco (NtFAD3), on separate plasmids, were introduced by particle bombardment. Co-integration, co-expression and inheritance of these genes were analyzed as well as seed fertility of the transgenic plants. Twenty-three out of 32 bialaphos-resistant plants integrated the NtFAD3 gene, which was confirmed by Southern-blot analysis of R0 plants, and showed one to more than 20 hybridizing bands of exogenous DNA, indicating a 72% (23/32) co-integration frequency. However, the frequency of the transgenic plants containing the 1.4-kb fragment of NtFAD3 gene was 34% (11/32). Northern-blot analysis revealed that seven out of ten fertile transgenic rice plants which had a 1.4-kb fragment of NtFAD3 cDNA expressed NtFAD3 mRNA. The NtFAD3 gene under the control of CaMV35S promoter stably expressed in the transgenic rice plants and modified the proportions of linoleic acid (18:2) and linolenic acid (18:3) in fatty acids; the content of 18:2 decreased and that of 18:3 increased. Fourteen out of 32 (44%) transgenic plants set seeds and 18 (56%) showed low fertility or sterility. Molecular analysis of the selfed progeny indicated that all copies in almost all R0 plants were inherited as a single dominant hemizygous locus.