title: Depletion of the xynB2 gene upregulates β-xylosidase expression in C. crescentus.
abstract: Caulobacter crescentus is able to express several enzymes involved in the utilization of lignocellulosic biomasses. Five genes, xynB1-5, that encode β-xylosidases are present in the genome of this bacterium. In this study, the xynB2 gene, which encodes β-xylosidase II (CCNA_02442), was cloned under the control of the PxylX promoter to generate the O-xynB2 strain, which overexpresses the enzyme in the presence of xylose. In addition, a null mutant strain, Δ-xynB2, was created by two homologous recombination events where the chromosomal xynB2 gene was replaced by a copy that was disrupted by the spectinomycin-resistant cassette. We demonstrated that C. crescentus cells lacking β-xylosidase II upregulates the xynB genes inducing β-xylosidase activity. Transcriptional analysis revealed that xynB1 (RT-PCR analysis) and xynB2 (lacZ transcription fusion) gene expression was induced in the Δ-xynB2 cells, and high β-xylosidase activity was observed in the presence of different agro-industrial residues in the null mutant strain, a characteristic that can be explored and applied in biotechnological processes. In contrast, overexpression of the xynB2 gene caused downregulation of the expression and activity of the β-xylosidase. For example, the β-xylosidase activity that was obtained in the presence of sugarcane bagasse was 7-fold and 16-fold higher than the activity measured in the C. crescentus parental and O-xynB2 cells, respectively. Our results suggest that β-xylosidase II may have a role in controlling the expression of the xynB1 and xynB2 genes in C. crescentus.
authors.affiliation: Centro de Ciências Exatas e Tecnológicas, Universidade Estadual do Oeste do Paraná, Cascavel, Brazil.
authors.forename: Juliana Moço
authors.initials: JM
authors.lastname: Corrêa
authors.forename: Moara Rodrigues
authors.initials: MR
authors.lastname: Mingori
authors.forename: Rinaldo Ferreira
authors.initials: RF
authors.lastname: Gandra
authors.forename: Eduardo Alexandre
authors.initials: EA
authors.lastname: Loth
authors.forename: Flávio Augusto Vicente
authors.initials: FA
authors.lastname: Seixas
authors.forename: Rita de Cássia Garcia
authors.initials: Rde C
authors.lastname: Simão
mesh_terms: D016935:Caulobacter crescentus / Q000201:enzymology* / Q000235:genetics*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D007221:Industry; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000235:genetics*; D014995:Xylosidases / Q000235:genetics* / Q000378:metabolism
chemical_list: D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase