AUTHOR=Mao Meng-Ying , Yang Ying-Ming , Li Ke-Zeng , Lei Lei , Li Meng , Yang Yan , Tao Xiang , Yin Jia-Xin , Zhang Ru , Ma Xin-Rong , Hu Tao 

TITLE=The rnc Gene Promotes Exopolysaccharide Synthesis and Represses the vicRKX Gene Expressions via MicroRNA-Size Small RNAs in Streptococcus mutans

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00687

DOI=10.3389/fmicb.2016.00687

ISSN=1664-302X

ABSTRACT=<p>Dental caries is a biofilm-dependent disease that largely relies on the ability of <italic>Streptococcus mutans</italic> to synthesize exopolysaccharides. Although the <italic>rnc</italic> gene is suggested to be involved in virulence mechanisms in many other bacteria, the information regarding it in <italic>S. mutans</italic> is very limited. Here, using deletion or overexpression mutant assay, we demonstrated that <italic>rnc</italic> in <italic>S. mutans</italic> significantly positively regulated exopolysaccharide synthesis and further altered biofilm formation. Meanwhile, the cariogenecity of <italic>S. mutans</italic> was decreased by deletion of <italic>rnc</italic> in a specific pathogen-free (SPF) rat model. Interestingly, analyzing the expression at mRNA level, we found the downstream <italic>vic</italic> locus was repressed by <italic>rnc</italic> in <italic>S. mutans</italic>. Using deep sequencing and bioinformatics analysis, for the first time, three putative microRNA-size small RNAs (msRNAs) targeting <italic>vicRKX</italic> were predicted in <italic>S. mutans</italic>. The expression levels of these msRNAs were negatively correlated with <italic>vicRKX</italic> but positively correlated with <italic>rnc</italic>, indicating <italic>rnc</italic> probably repressed <italic>vicRKX</italic> expression through msRNAs at the post-transcriptional level. In all, the results present that <italic>rnc</italic> has a potential role in the regulation of exopolysaccharide synthesis and can affect <italic>vicRKX</italic> expressions via post-transcriptional repression in <italic>S. mutans</italic>. This study provides an alternative avenue for further research aimed at preventing caries.</p>