Elucidation of an Array of Nitrate Transporter Paralogs in Arabidopsis Thaliana Genome

Plants derive gene paralogs after both small-scale duplication (SSD) and whole genome duplication (WGD). Plants are known to retain duplicated genes and enhance their gene repertoire which intensively contributes to the evolution of their genomes. The general view is that such paralogs are both selected and preserved in evolution because they express variable levels of proteins in different temporal and spatial patterns. In Arabidopsis thaliana, paralogs involved in signalling and transcriptional regulation are very often retained after gene and genome duplication events. We analysed duplication events of a primitive nitrate transporter gene NTR across the genome of Arabidopsis thaliana. Majority of the paralogs have acquired the function of both high, low and also dual affinity nitrate transporters, some being regulated by nitrate levels themselves and involved in a variety of plant functions such as embryonic development, repression of lateral root initiation, stomatal opening, xylem and phloem transport and wound response etc. For the present analysis, 19 nitrate transporter protein sequences were retrieved from TAIR database and analysed by a web service tool PINDA as well as manually which gave analogous results. Several transporters were found to be acting as paralogs as close sequence homology was observed amongst them. The results point towards the idea that sub functionalization of nitrate transporter proteins in higher plants happened as a result of a series of gene duplication events.