Horizontal gene transfer from Agrobacterium to plants

Abstract

Most genetic engineering of plants uses Agrobacterium mediated transformation to introduce novel gene content. In nature, insertion of T-DNA in the plant genome and its subsequent transfer via sexual reproduction has been shown in several species in the genera Nicotiana and Linaria. In these natural examples of horizontal gene transfer from Agrobacterium to plants, the T-DNA donor is assumed to be a mikimopine strain of A. rhizogenes. A sequence homologous to the T-DNA of the Ri plasmid of Agrobacterium rhizogenes was found in the genome of untransformed Nicotiana glauca about 30 years ago, and was named “cellular T-DNA” (cT-DNA). It represents an imperfect inverted repeat and contains homologs of several T-DNA oncogenes (NgrolB, NgrolC, NgORF13, NgORF14) and an opine synthesis gene (Ngmis). A similar cT-DNA has also been found in other species of the genus Nicotiana. These presumably ancient homologs of T-DNA genes are still expressed, indicating that they may play a role in the evolution of these plants. Recently T-DNA has been detected and characterized in Linaria vulgaris and L. dalmatica. In Linaria vulgaris the cT-DNA is present in two copies and organized as a tandem imperfect direct repeat, containing LvORF2, LvORF3, LvORF8, LvrolA, LvrolB, LvrolC, LvORF13, LvORF14, and the Lvmis genes. All L. vulgaris and L. dalmatica plants screened contained the same T-DNA oncogenes and the mis gene. Evidence suggests that there were several independent T-DNA integration events into the genomes of these plant genera. We speculate that ancient plants transformed by A. rhizogenes might have acquired a selective advantage in competition with the parental species. Thus, the events of T-DNA insertion in the plant genome might have affected their evolution, resulting in the creation of new plant species. In this review we focus on the structure and functions of cT-DNA in Linaria and Nicotiana and discuss their possible evolutionary role.

The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop

“…A PCR and hybridization-based search for naturally transgenic species in the family Solanaceae was conducted without success (23). However, a subsequent, more extensive search resulted in the identification of A. rhizogeneshomologous T-DNA sequences in Linaria vulgaris (27,28). Neither Nicotiana nor Linaria are food crops, and such findings have so far not been associated with domesticated edible crops.…”

Genetic Engineering and Sustainable Crop Disease Management: Opportunities for Case-by-Case Decision-Making

“…Naturally produced recombinant DNA can result from: meiotic recombination; the action of diverse and often abundant mobile genetic elements; gene duplication; chromosomal inversions and translocations; novel gene assemblies; shuffling of exons and other gene fragments; chromosomal duplication; horizontal gene transfer; and incorporation of viral genes. In fact, all land plants appear to be "natural GMOs," as all contain genes apparently acquired horizontally [178][179][180][181][182][183][184][185][186][187][188][189][190][191][192][193][194]. To my knowledge, there is no published, validated research showing any fundamental biochemical or biophysical difference between DNA recombined in a test tube vs. that recombined in a living cell.…”

Homologs of the rolC gene of naturally transgenic toadflaxes Linaria vulgaris and Linaria creticola are expressed in vitro

“…свидетельствуют о том, что наиболее консервативным ге-ном с ненарушенной ОРС является rolC (Matveeva, Lutova, 2014). L. vulgaris и L. acutiloba относятся к секции Linaria, L. genistifolia -к секции Speciosae, L. acutiloba иногда рас-сматривают как подвид L. vulgaris (www.plantarium.ru).…”