Comparative Genomics Of CAZyme Domain Frequency and Diversity In Eucalyptus grandis and Other Land Plants

CAZyme protein domains are important functional building blocks of enzymes that metabolize polysaccharides. In plants, CAZyme domain containing proteins are responsible for the synthesis and modification of industrially important biopolymers such as cellulose and xylan found in abundance in secondary xylem. An understanding of the association between CAZyme domain diversity and carbohydrate metabolism in plants, especially potential bioenergy crop species such as Eucalyptus grandis and Populus trichocarpa, is essential for the efficient utilization of lignocellulosic biomass. Previous studies have suggested that the genomic investment in CAZyme genes was greater in the woody perennial Populus trichocarpa than that in the herbaceous annual Arabidopsis thaliana. We investigated the frequency and diversity of CAZyme families in the genomes of 22 plant species available on Phytozome. We find that the relative ratios of CAZyme domain classes have been largely retained across the plant evolutionary spectrum, but with reduced diversity of families in more complex plants indicating that the retention of a basic suite of CAZymes is a feature of land plants. Our results suggest that the genomic potential to form cell wall carbohydrates is similar among all plants, but it is the utilization and scale of expression of specific CAZyme containing genes that allow secondary cell wall biopolymers to be deposited in vast quantities during wood formation in fast-growing trees such as Eucalyptus and Populus. These results will aid in focusing our search to understand and modify carbohydrate metabolism in plants with the potential to be used as feedstocks for biofuels and biomaterials.