cT-DNA in Linaria vulgaris L. is multicopy, inverted and homogenized

The phenomenon of evolutionary fixation of agrobacterial sequences (cT-DNA or cellular transferred DNA) in plant genomes is well known in nature. It was previously considered, that all of cT-DNA-containing species, except Linaria vulgaris , have multiple inverted cT-DNA repeats. Deep studying of general features of cT-DNA brings us closer to understanding the causes and mechanisms of its fixation in plants genomes. We combined multiple long-range PCR with genome walking for studying extended structure of cT-DNA. Using digital PCR method, we estimated copy number of cT-DNA elements. NGS with low covering allows us to develop a set of microsatellite markers, also used for copy number estimation. According to new data, cT-DNA elements in L. vulgaris form an inverted complex repeat of two simple direct repeats. After cT-DNA integration, cT-DNA sequence duplication events took place at least two times. The phenomenon of concerted evolution of cT-DNA sequences as well as some details of this process have been shown for the first time. We have shown, that L. vulgaris, as well as other cT-DNA containing species, has inverted structure of repeats. This fact indicates possible existence of some general causes and mechanisms of cT-DNA fixation in plant genomes during evolution.