rol Genes of Agrobacteria: Possible Biological Functions

Abstract—As a result of agrobacterium-mediated transformation, the rolA, rolB, rolC, and rolD genes of Agrobacterium rhizogenes are integrated into plant genomes as parts of T-DNA. These genes cause abundant growth of hairy roots, and the regeneration of shoots from them causes short stature, shortening of internodes and wrinkled leaves. A sufficient number of representatives of the genera Nicotiana, Linaria, Ipomoea, and others in their genome contain some rol genes that entered them during horizontal gene transfer and were evolutionarily fixed. The conservatism of the rol genes of A. rhizogenes in naturally transgenic plants can probably be associated with the performance of important biological functions by them. The purpose of this article is to review the currently available data on the biological role of rol genes in hairy roots, transformed plants, and naturally transgenic plants. The results of scientific studies published to date describe the expression of rol genes both together and separately. It should be noted that expression has a different effect on the morphology of both plants transformed by agrobacteria and naturally transgenic species. The review presents the results of studies that have shown a positive effect of rol genes on secondary metabolism, the antioxidant system and plant stress resistance. The question of the possible effect of protein products of rol genes through the influence on the content of phytohormones or sensitivity to them is also discussed. Experimental evidence of subcellular localization of Rol proteins and enzymatic activity of Rol proteins with respect to phytohormone glucosides are described. However, these experiments did not give exhaustive answers, and, therefore, studies of the biological functions of the rol genes should be continued. This knowledge can be used to create transgenic and genome-edited plants that have economically valuable traits.