Functional and Evolutionary Characterization of a UDP-Xylose Synthase Gene from the Plant Pathogen <i>Xylella fastidiosa</i>, Involved in the Synthesis of Bacterial Lipopolysaccharide

<i>Xylella fastidiosa</i> is a plant-infecting bacillus, responsible for many important crop diseases, such as Pierce’s disease of vineyards, citrus variegated chlorosis, and coffee leaf scorch (CLS), among others. Recent genomic comparisons involving two CLS-related strains, belonging to <i>X. fastidiosa</i> subsp. <i>pauca</i>, revealed that one of them carries a frameshift mutation that inactivates a gene encoding an oxidoreductase of the short-chain dehydrogenase/reductase (SDR) superfamily, which may play important roles in determining structural variations in bacterial glycans and glycoconjugates. However, the exact nature of this SDR has been a matter of controversy, as different annotations of <i>X. fastidiosa</i> genomes have implicated it in distinct reactions. To confirm the nature of this mutated SDR, a comparative analysis was initially performed, suggesting that it belongs to a subgroup of SDR decarboxylases, representing a UDP-xylose synthase (Uxs). Functional assays, using a recombinant derivative of this enzyme, confirmed its nature as <i>Xf</i>Uxs, and carbohydrate composition analyses, performed with lipopolysaccharide (LPS) molecules obtained from different strains, indicate that inactivation of the <i>X. fastidiosa uxs</i> gene affects the LPS structure among CLS-related <i>X. fastidiosa</i> strains. Finally, a comparative sequence analysis suggests that this mutation is likely to result in a morphological and evolutionary hallmark that differentiates two subgroups of CLS-related strains, which may influence interactions between these bacteria and their plant and/or insect hosts

Functional and Evolutionary Characterization of a UDP-Xylose Synthase Gene from the Plant Pathogen <i>Xylella fastidiosa</i>, Involved in the Synthesis of Bacterial Lipopolysaccharide

<i>Xylella fastidiosa</i> is a plant-infecting bacillus, responsible for many important crop diseases, such as Pierce’s disease of vineyards, citrus variegated chlorosis, and coffee leaf scorch (CLS), among others. Recent genomic comparisons involving two CLS-related strains, belonging to <i>X. fastidiosa</i> subsp. <i>pauca</i>, revealed that one of them carries a frameshift mutation that inactivates a gene encoding an oxidoreductase of the short-chain dehydrogenase/reductase (SDR) superfamily, which may play important roles in determining structural variations in bacterial glycans and glycoconjugates. However, the exact nature of this SDR has been a matter of controversy, as different annotations of <i>X. fastidiosa</i> genomes have implicated it in distinct reactions. To confirm the nature of this mutated SDR, a comparative analysis was initially performed, suggesting that it belongs to a subgroup of SDR decarboxylases, representing a UDP-xylose synthase (Uxs). Functional assays, using a recombinant derivative of this enzyme, confirmed its nature as <i>Xf</i>Uxs, and carbohydrate composition analyses, performed with lipopolysaccharide (LPS) molecules obtained from different strains, indicate that inactivation of the <i>X. fastidiosa uxs</i> gene affects the LPS structure among CLS-related <i>X. fastidiosa</i> strains. Finally, a comparative sequence analysis suggests that this mutation is likely to result in a morphological and evolutionary hallmark that differentiates two subgroups of CLS-related strains, which may influence interactions between these bacteria and their plant and/or insect hosts