Xylan Utilization Regulon in Xanthomonas citri pv. citri Strain 306: Gene Expression and Utilization of Oligoxylosides

摘要: Xanthomonas citri pv. strain 306 (Xcc306), a causative agent of citrus canker, produces endoxylanases that catalyze the depolymerization cell wall-associated xylans. In sequenced genomes all plant-pathogenic xanthomonads, genes encoding xylanolytic enzymes are clustered in three adjacent operons. Xcc306, these consecutive operons contain glycoside hydrolase family 10 (GH10) Xyn10A and Xyn10C, agu67 gene, GH67 α-glucuronidase (Agu67), xyn43E putative GH43 α-l-arabinofuranosidase, xyn43F β-xylosidase. Recombinant Xyn10C convert polymeric 4-O-methylglucuronoxylan (MeGXn) to oligoxylosides methylglucuronoxylotriose (MeGX3), xylotriose (X3), xylobiose (X2). Xcc306 completely utilizes MeGXn predigested with or but shows little utilization MeGXn. deletion gene (Xcc306 Δagu67) will not utilize MeGX3 for growth, demonstrating role Agu67 complete GH10-digested Preferential growth on compared indicates GH10 xylanases, either secreted by planta produced plant host, generate processed Xyn10 xylanases residing periplasm. Coordinate induction xyn10, agu67, cirA, tonB receptor, other within they constitute regulon is responsive generated action The combined expression this may allow scavenging derived from wall deconstruction, thereby contributing tissue colonization and/or survival and, ultimately, disease.