AUTHOR=Matveeva Tatiana V. , Lutova Ludmila A. 

TITLE=Horizontal gene transfer from Agrobacterium to plants

JOURNAL=Frontiers in Plant Science

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2014.00326

DOI=10.3389/fpls.2014.00326

ISSN=1664-462X

ABSTRACT=<p>Most genetic engineering of plants uses <italic>Agrobacterium</italic> 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 <italic>Nicotiana</italic> and <italic>Linaria</italic>. In these natural examples of horizontal gene transfer from <italic>Agrobacterium</italic> to plants, the T-DNA donor is assumed to be a mikimopine strain of <italic>A. rhizogenes</italic>. A sequence homologous to the T-DNA of the Ri plasmid of <italic>Agrobacterium rhizogenes</italic> was found in the genome of untransformed <italic>Nicotiana glauca</italic> 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 (Ng<italic>rolB</italic>, Ng<italic>rol</italic>C, NgORF13, NgORF14) and an opine synthesis gene (Ng<italic>mis)</italic>. A similar cT-DNA has also been found in other species of the genus <italic>Nicotiana</italic>. 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 <italic>Linaria vulgaris</italic> and <italic>L. dalmatica</italic>. In <italic>Linaria vulgaris</italic> the cT-DNA is present in two copies and organized as a tandem imperfect direct repeat, containing Lv<italic>ORF2</italic>, Lv<italic>ORF3</italic>, Lv<italic>ORF8</italic>, Lv<italic>rolA</italic>, Lv<italic>rolB</italic>, Lv<italic>rolC</italic>, Lv<italic>ORF13</italic>, Lv<italic>ORF14</italic>, and the Lv<italic>mis</italic> genes. All <italic>L. vulgaris</italic> and <italic>L. dalmatica</italic> plants screened contained the same T-DNA oncogenes and the <italic>mis</italic> 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 <italic>A. rhizogenes</italic> 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 <italic>Linaria</italic> and <italic>Nicotiana</italic> and discuss their possible evolutionary role.</p>