Thioredoxin H (TrxH) contributes to adversity adaptation and pathogenicity of Edwardsiella piscicida
2019
Wang, Bi-ying | Huang, Hui-qin | Li, Shuang | Tang, Ping | Dai, Hao-fu | Xian, Jian-an | Sun, Dong-mei | Hu, Yong-hua
Thioredoxins (Trxs) play an important role in defending against oxidative stress and keeping disulfide bonding correct to maintain protein function. Edwardsiella piscicida, a severe fish pathogen, has been shown to encode several thioredoxins including TrxA, TrxC, and TrxH, but their biological roles remain unknown. In this study, we characterized TrxH of E. piscicida (named TrxHEₚ) and examined its expression and function. TrxHEₚ is composed of 125 residues and possesses typical thioredoxin H motifs. Expression of trxHEₚ was upregulated under conditions of oxidative stress, iron starvation, low pH, and during infection of host cells. trxHEₚ expression was also regulated by ferric uptake regulator (Fur), an important global regulatory of E. piscicida. Compared to the wild type TX01, a markerless trxHEₚ in-frame mutant strain TX01∆trxH exhibited markedly compromised tolerance of the pathogen to hydrogen peroxide, acid stress, and iron deficiency. Deletion of trxHEₚ significantly retarded bacterial biofilm growth and decreased resistance against serum killing. Pathogenicity analysis shows that the inactivation of trxHEₚ significantly impaired the ability of E. piscicida to invade host cells, reproduce in macrophages, and infect host tissues. Introduction of a trans-expressed trxH gene restored the lost virulence of TX01∆trxH. There is likely to be a complex relationship of functional complementation or expression regulation between TrxH and another two thioredoxins, TrxA and TrxC, of E. piscicida. This is the first functional report of TrxH in fish pathogens, and the findings suggest that TrxHEₚ is essential for coping with adverse circumstances and contributes to host infection of E. piscicida.
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