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Yan Cheng,Youjun Feng,Ping Luo,Jiang Gu,Shu Yu,Wei-jun Zhang,Yan-qing Liu,Qing-xu Wang,Quan-ming Zou,Xu-hu Mao 한국미생물학회 2009 The journal of microbiology Vol.47 No.4
Shiga toxin 2 (Stx2) is a major virulence factor for enterohemorrhagic Escherichia coli (EHEC), which is encoded by λ lysogenic phage integrated into EHEC chromosome. Stx2A1, A1 subunit of Stx2 toxin has gathered extensive concerns due to its potential of being developed into a vaccine candidate. However, the substantial progress is hampered in part for the lack of a suitable in vitro expression system. Here we report use of the prokaryotic system pET-28a::espA-Stx2A1/BL21 to carry out the fusion expression of Stx2A1 which is linked to E. coli secreted protein A (EspA) at its N-terminus. Under the IPTG induction, EspA- Stx2A1 fusion protein in the form of inclusion body was obtained successfully, whose expression level can reach about 40% of total bacterial protein at 25°C, much higher than that at 37°C. Western blot test suggested the refolded fusion protein is of excellent immuno-reactivity with both monoclonal antibodies, which are specific to EspA and Stx2A1, respectively. Anti-sera from Balb/c mice immunized with the EspA-Stx2A1 fusion protein were found to exhibit strong neutralization activity and protection capability in vitro and in vivo. These data have provided a novel feasible method to produce Stx2A1 in large scale in vitro, which is implicated for the development of multivalent subunit vaccines candidate against EHEC O157:H7 infections.
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Min Cao,Youjun Feng,Changjun Wang,Feng Zheng,Ming Li,Hui Liao,Yinghua Mao,Xiuzhen Pan,Jing Wang,Dan Hu,Fuquan Hu,Jiaqi Tang 한국미생물학회 2011 The journal of microbiology Vol.49 No.6
Quorum sensing is a widespread chemical communication in response to fluctuation of bacterial population density, and has been implicated into bacterial biofilm formation and regulation of expression of virulence factors. The luxS gene product, S-ribosylhomocysteinase, catalizes the last committed step in biosynthetic pathway of autoinducer 2 (AI-2), a signaling molecule for inter-species quorum sensing. We found a luxS homologue in 05ZYH33, an epidemic strain of Streptococcus suis serotype 2 (SS2) in China. A luxS null mutant (ΔluxS) of 05ZYH33 strain was obtained using an approach of homologous recombination. LuxS was determined to be required for AI-2 production in 05ZYH33 strain of S. suis 2. Inactivation of luxS gene led to a wide range of phenotypic changes including thinner capsular walls, increased tolerance to H_2O_2, reduced adherence capacity to epithelial cells, etc. In particular, loss of LuxS impaired dramatically its full virulence of SS2 in experimental model of piglets, and functional complementation restored it nearly to the level of parent strain. Genome-wide transcriptome analyses suggested that some known virulence factors such as CPS are down-regulated in the ΔluxS mutant, which might in part explain virulence attenuation by luxS deletion. Similarly, 29 of 71 genes with different expression level were proposed to be targets candidate regulated by LuxS/AI-2-dependent quorum sensing.
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Chang Liu,Xiaoxu Yang,Zhishan Yan,Youjun Fan,Guojun Feng,Dajun Liu 한국유전학회 2019 Genes & Genomics Vol.41 No.12
and quality. At present, little is known about the genes and molecular regulation mechanism in cold response in snap bean exposed to low temperature. Objectives Our objectives were to identify the low temperature response genes in snap bean and to examine differences in the gene response between cold-tolerant and cold-sensitive genotypes. Methods We used two highly inbred snap bean lines in this study, the cold-tolerant line ‘120’, and the cold-sensitive line ‘093’. The plants were grown to the three leaf and one heart stage and exposed to 4 °C low temperature. We used RNA sequencing (RNA-seq) to analyze the differences of gene expression. Results 988 and 874 cold-responsive genes were identified in ‘T120 vs CK120’ and ‘T093 vs CK093’ (‘T’ stands for low temperature treatment, and ‘CK’ stands for control at room temperature), respectively. Of these, 555 and 442 genes were unique to cold-stressed lines ‘120’ and ‘093’, respectively compared to the control. Our analysis of these differentially expressed genes indicates that Ca2+, ROS, and hormones act as signaling molecules that play important roles in low temperature response in P. vulgaris. Altering the expression of genes in these signaling pathways activates expression of downstream response genes which can interact with other signaling regulatory networks. This may maintained the balance of ROS and hormones, making line ‘120’ more cold-tolerant than line ‘093’. Conclusion Our results provide a preliminarily understanding of the molecular basis of low temperature response in snap bean, and also establish a foundation for the future genetic improvement of cold sensitivity in snap bean by incorporating genes for cold tolerance.
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