Natural GMOs in the genus Nicotiana L.

Soil bacteria Agrobacterium are able to transfer fragments of their plasmids, so-called T-DNA, into plants. T-DNA integrated into plants genome is called cellular T-DNA (cT-DNA) [1]. Plants transformed in nature are considered natural genetically modified organisms (nGMOs). For the first time, nGMOs were described within the genus Nicotiana. To date, more than 50 nGM species are known [2, 3], among which nGMO in the genus Nicotiana are the most well studied. Within this genus 3 subgenera are distinguished, those are Tabacum, Petunioides, and Rustica. CT-DNAs in natural genetically modified representatives of the subgenus Tabacum are studied in detail [4, 5]. We know how many cT-DNA those species carry as well as the composition of the cT-DNA, which allows us to propose scenarios for the acquisition of cT-DNA by these species during their evolution. Species N. noctiflora and N. glauca belong to the subgenus Petunioides and they are not so well studied. We sequenced and assembled the genomes of N. noctiflora and N. glauca, to analyze their cT-DNAs. In the N. glauca genome we confirmed the presence of one cT-DNA, gT, discovered in 1983, and showed no other inserts. In the genome of N. noctiflora 2 cT-DNAs of different composition were found, NnT-DNA1 and NnT-DNA2. The data suggest a single agrotransformation act in the evolution of the species N. glauca, while the species N. noctiflora was transformed several times. Further study of cT-DNA in Nicotiana representatives belonging to different evolutionary branches of the genus will help to clarify the evolutionary history of the genus Nicotiana. In addition, the identification of changes that have occurred in the cT-DNA since its entry into the plant genome will help to elucidate the processes that occur with transgenes in plant genomes over long time intervals. 
The work was supported by the Russian Science Foundation (21-14-00050) and was conducted using the equipment of the Research Center of St. Petersburg State University BioBank. The authors are grateful to professor Leon Otten, as well as Pavel Dobrynin, Dmitry Polev, Nikolai Ivanov, and Nicholas Sierro.