Evolutionary Fate of the Opine Synthesis Genes in the Arachis L. Genomes

Naturally transgenic plants are plants that have undergone <i>Agrobacterium</i>-mediated transformation under natural conditions without human involvement. Among <i>Arachis hypogaea</i> L., <i>A. duranensis</i> Krapov. & W.C. Greg, <i>A</i>. <i>ipaensis</i> Krapov. & W.C. Greg, <i>A. monticola</i> Krapov. & Rigoni, and <i>A. stenosperma</i> Krapov. & W.C. Greg are known to contain sequences derived from the T-DNA of "<i>Agrobacterium</i>". In the present study, using molecular genetics and bioinformatic methods, we characterized natural transgenes in 18 new species from six sections of the genus <i>Arachis</i>. We found that small fragments of genes for enzymes of the agropine synthesis pathway were preserved only in some of the studied samples and were lost in the majority of the species during evolution. At the same time, genes, similar to cucumopine synthases (<i>cus</i>-like), remained intact in almost all of the investigated species. In cultivated peanuts, they are expressed in a tissue-specific manner. We demonstrated the intraspecific variability of the structure and expression of the <i>cus</i>-like gene in cultivated peanuts. The described diversity of gene sequences horizontally transferred from <i>Agrobacterium</i> to plants helps to shed light on the phylogeny of species of the genus <i>Arachis</i> and track possible hybridization events. Data on the ability of certain species to hybridize are useful for planning breeding schemes aimed at transferring valuable traits from wild species into cultivated peanuts.