Depletion of the xynB2 Gene Upregulates beta-Xylosidase Expression in C. crescentus

作者：Correa Juliana Moco; Mingori Moara Rodrigues; Gandra Rinaldo Ferreira; Loth Eduardo Alexandre; Vicente Seixas Flavio Augusto; Simao Rita de Cssia Garcia^*

来源：Applied Biochemistry and Biotechnology, 2014, 172(2): 1085-1097.

DOI：10.1007/s12010-013-0549-8

• Caulobacter crescentus
• beta-xylosidase
• Gene expression
• Xylose
• Mutant cells
• Agro-industrial residue

Caulobacter crescentus is able to express several enzymes involved in the utilization of lignocellulosic biomasses. Five genes, xynB1-5, that encode beta-xylosidases are present in the genome of this bacterium. In this study, the xynB2 gene, which encodes beta-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, Delta-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 beta-xylosidase II upregulates the xynB genes inducing beta-xylosidase activity. Transcriptional analysis revealed that xynB1 (RT-PCR analysis) and xynB2 (lacZ transcription fusion) gene expression was induced in the Delta-xynB2 cells, and high beta-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 beta-xylosidase. For example, the beta-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 beta-xylosidase II may have a role in controlling the expression of the xynB1 and xynB2 genes in C. crescentus.

• 出版日期2014-1