Systems identification and characterization of β-glucuronosyltransferase genes involved in arabinogalactan-protein biosynthesis in plant genomes

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Utilizing plant biomass for bioethanol production requires an understanding of the molecular mechanisms involved in plant cell wall assembly. Arabinogalactan-proteins (AGPs) are glycoproteins that interact with other cell wall polymers to influence plant growth and developmental processes. Glucuronic acid, which is transferred to the AGP glycan by β-glucuronosyltransferases (GLCATs), is the only acidic sugar in AGPs with the ability to bind calcium. We carried out a comprehensive genome-wide analysis of a putative GLCAT gene family involved in AGP biosynthesis by examining its sequence diversity, genetic architecture, phylogenetic and motif characteristics, selection pressure and gene expression in plants. We report the identification of 161 putative GLCAT genes distributed across 14 plant genomes and a widely conserved GLCAT catalytic domain. We discovered a phylogenetic clade shared between bryophytes and higher land plants of monocot grass and dicot lineages and identified positively selected sites that do not result in functional divergence of GLCATs. RNA-seq and microarray data analyses of the putative GLCAT genes revealed gene expression signatures that likely influence the assembly of plant cell wall polymers which is critical to the overall growth and development of edible and bioenergy crops.