Abstract: //Agrobacterium rhizogenes// and //Agrobacterium tumefaciens// are plant pathogenic bacteria capable of transferring DNA fragments [transfer DNA (T-DNA)] bearing functional genes into the host plant genome. This naturally occurring mechanism has been adapted by plant biotechnologists to develop genetically modified crops that today are grown on more than 10% of the world’s arable land, although their use can result in considerable controversy. While assembling small interfering RNAs, or siRNAs, of sweet potato plants for metagenomic analysis, sequences homologous to T-DNA sequences from //Agrobacterium// spp. were discovered. Simple and quantitative PCR, Southern blotting, genome walking, and bacterial artificial chromosome library screening and sequencing unambiguously demonstrated that two different T-DNA regions (//Ib//T-DNA1 and //Ib//T-DNA2) are present in the cultivated sweet potato (//Ipomoea batatas// [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. //Ib//T-DNA1 was found to contain four open reading frames (ORFs) homologous to the tryptophan-2-monooxygenase (//iaaM//), indole-3-acetamide hydrolase (//iaaH//), C-protein (//C-prot//), and agrocinopine synthase (//Acs//) genes of //Agrobacterium// spp. //Ib//T-DNA1 was detected in all 291 cultigens examined, but not in close wild relatives. //Ib//T-DNA2 contained at least five ORFs with significant homology to the //ORF14//, //ORF17n//, rooting locus (//Rol//)//B/////RolC//, //ORF13//, and //ORF18/////ORF17n// genes of //A. rhizogenes//. //Ib//T-DNA2 was detected in 45 of 217 genotypes that included both cultivated and wild species. Our finding, that sweet potato is naturally transgenic while being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops. | Abstract: //Agrobacterium rhizogenes// and //Agrobacterium tumefaciens// are plant pathogenic bacteria capable of transferring DNA fragments [transfer DNA (T-DNA)] bearing functional genes into the host plant genome. This naturally occurring mechanism has been adapted by plant biotechnologists to develop genetically modified crops that today are grown on more than 10% of the world’s arable land, although their use can result in considerable controversy. While assembling small interfering RNAs, or siRNAs, of sweet potato plants for metagenomic analysis, sequences homologous to T-DNA sequences from //Agrobacterium// spp. were discovered. Simple and quantitative PCR, Southern blotting, genome walking, and bacterial artificial chromosome library screening and sequencing unambiguously demonstrated that two different T-DNA regions (//Ib//T-DNA1 and //Ib//T-DNA2) are present in the cultivated sweet potato (//Ipomoea batatas// [L.] Lam.) genome and that these foreign genes are expressed at detectable levels in different tissues of the sweet potato plant. //Ib//T-DNA1 was found to contain four open reading frames (ORFs) homologous to the tryptophan-2-monooxygenase (//iaaM//), indole-3-acetamide hydrolase (//iaaH//), C-protein (//C-prot//), and agrocinopine synthase (//Acs//) genes of //Agrobacterium// spp. //Ib//T-DNA1 was detected in all 291 cultigens examined, but not in close wild relatives. //Ib//T-DNA2 contained at least five ORFs with significant homology to the //ORF14//, //ORF17n//, rooting locus (//Rol//)//B/////RolC//, //ORF13//, and //ORF18/////ORF17n// genes of //A. rhizogenes//. //Ib//T-DNA2 was detected in 45 of 217 genotypes that included both cultivated and wild species. Our finding, that sweet potato is naturally transgenic while being a widely and traditionally consumed food crop, could affect the current consumer distrust of the safety of transgenic food crops. |