Gene-expression analysis of cold-stress response in the sexually transmitted protist Trichomonas vaginalis

Background: Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common nonviral sexually transmitted disease in the world. This infection affects millions of individuals worldwide annually. Although direct sexual contact is the most common mode of transmission, increasing evidence indicates that T. vaginalis can survive in the external environment and can be transmitted by contaminated utensils. We found that the growth of T. vaginalis under cold conditions is greatly inhibited, but recovers after placing these stressed cells at the normal cultivation temperature of 37°C. However, the mechanisms by which T. vaginalis regulates this adaptive process are unclear. Methods: An expressed sequence tag (EST) database generated from a complementary DNA library of T. vaginalis messenger RNAs expressed under cold-culture conditions (4°C, TvC) was compared with a previously published normal-cultured EST library (37°C, TvE) to assess the cold-stress responses of T. vaginalis. Results: A total of 9780 clones were sequenced from the TvC library and were mapped to 2934 genes in the T. vaginalis genome. A total of 1254 genes were expressed in both the TvE and TvC libraries, and 1680 genes were only found in the TvC library. A functional analysis showed that cold temperature has effects on many cellular mechanisms, including increased H₂O₂ tolerance, activation of the ubiquitin-proteasome system, induction of iron-sulfur cluster assembly, and reduced energy metabolism and enzyme expression. Conclusion: The current study is the first large-scale transcriptomic analysis in cold-stressed T. vaginalis and the results enhance our understanding of this important protist.