Homologues of octopine/vitopine synthase genes in natural GMOs

The process of horizontal gene transfer causes the appearance of natural genetically modified organisms. At the moment, it is known that over 7% of dicotyledonous plant species are naturally transgenic, i.e. nGMO [1]. These plants contain the genes of agrobacteria, which are integrated in the nuclear genome during infection. In some species of naturally transgenic plants, agrobacterial genes have been preserved for millions of years of evolution. Among these genes, genes encoding octopine/vitopine synthase (ocs/vis) can be distinguished [2]. 
The study of homologues of octopin/vitopin synthase genes in naturally transgenic plants: their structures and diversity, products of encoded enzymes will allow us to establish the functions and evolutionary role of homologues in nGMO. Currently, bioinformatic and genetic engineering methods are used to solve these problems. 
ocs\vis-like were found in 7 species: Albizia julibrissin Durazz., Cenostigma pyramidale (Tul.) Gagnon G.P.Lewis, Paulownia fortunei (Seem.) Hemsl., Pterocarya stenoptera C.DC., Rehmannia glutinosa Steud., Santalum album L., Viscum album L. In total twenty one ocs/vis sequences are known in 17 nGMO species. Twenty sequences are intact. This may indicate the functional significance of these genes for nGMO. 
Phylogenetic analysis of currently known ocs/vis-like genes of Agrobacterium, Rhizobium and natural GMOs suggests that diversity of studied genes is wider, than it was estimated based on agrobacterial sequences. On the phylogenetic tree constructed by the neighbor-joining method, 6 clusters for ocs/vis can be distinguished. Three clusters contain nGMOs and agrobacteria, showing the relationship of the T-DNA sequences of nGMO with those of currently known strains of of Agrobacterium/Rhizobium. Three clusters contain only nGMOs. One of them consists of species that belong to the Cannabaceae family. Other clusters are heterogeneous. No significant ecological similarities were found among the studied species. 
The obtained results can be used to study the diversity of ancient and modern strains of agrobacteria, their host specificity and the possible role of their genes in plant evolution. 
The work was supported by the RSF, grant 21-14-00050 and Research Resource Center for molecular and cellular technologies of Saint Petersburg State University.