The number of homologs of some enzymes involved in tryptophan biosynthesis is correlated to the proportion of proteins associated with transcription in plants

Abstract

The tryptophan biosynthesis pathway is universal for the majority of known organisms, although it is absent in animals and some eubacteria. This pathway is conserved in plants, although various species differ in the number of paralogs of the enzymes involved in it. In this work, the possible role of the changes in the number of tryptophan biosynthesis enzymes paralogs in the course of evolution was analyzed. Towards this, the paralogs of the enzymes in tryptophan biosynthesis pathways were identified in plant species with fully sequenced genomes, and the relationship between the number of paralogs and the organismal complexity was assessed. It was demonstrated that organismal complexity statistically correlates with the number of tryptophan biosynthesis enzymes homologs, both with the total number of homologs and with the number of homologs for three of six enzymes, namely, ASA/ASB, PAI, and IGPS. This relationship may be accounted for by the increase in the organismal complexity and the number of tryptophan biosynthesis enzymes’ homologs being the mechanism of evolutionary adaptation to the varying conditions of the terrestrial environment in plants.