Enolase is an evolutionarily conserved enzyme involved in the processes of glycolysis and gluconeogenesis. Mycoplasma hyopneumoniae belongs to Mycoplasma , whose species are wall-less and among the smallest self-replicating bacteria, and is an important colonizing respiratory pathogen in the pig industry worldwide. Mycoplasma hyopneumoniae enolase ( Mhp Eno) expression is significantly increased after infection and was previously found to be a virulence factor candidate. Our studies show that Mhp Eno is a cell surface-localized protein that can adhere to swine tracheal epithelial cells (STECs). Adhesion to STECs can be specifically inhibited by an Mhp Eno antibody. Mhp Eno can recognize and interact with plasminogen with high affinity. Here, the first crystal structure of the mycoplasmal enolase from Mycoplasma hyopneumoniae was determined. The structure showed unique features of Mhp Eno in the S3/H1, H6/S6, H7/H8, and H13 regions. All of these regions were longer than those of other enolases and were exposed on the Mhp Eno surface, making them accessible to host molecules. These results show that Mhp Eno has specific structural characteristics and acts as a multifunctional adhesin on the Mycoplasma hyopneumoniae cell surface.
Mycoplasmas are a group of prokaryotes without cell walls that have evolved through several rounds of degenerative evolution. With a low cell DNA G + C content and definitively long genetic lineages, mycoplasmas are thought to be in a state of rapid evolution. However, little associated evidence has been provided. Enolase is a key enzyme in glycolysis that is widely found in all species from the three domains, and it is evolutionarily conserved. In our previous studies, enolase acted as a virulence factor and participated in cell-surface adhesion in Mycoplasma hyopneumoniae. Furthermore, unique loop regions were first found in the crystal structure of Mhp Eno. Here, enolase structures from Mycoplasma pneumoniae and Mycoplasma bovis were determined. An extra helix 7 is specific and conservatively found in almost all mycoplasma enolases, as confirmed by crystal structures and sequence alignment. Particular motifs for helix 7, which is composed of F-K/G-K-L/F-K-X-A-I, have been proposed and could be regarded as molecular markers. To our surprise, the genetic distances between any two mycoplasma enolases were obviously longer than those between the two corresponding species themselves, indicating divergent evolution of mycoplasma enolases, whereas no horizontal gene transfer was detected in mycoplasma enolase genens. Furthermore, different evolutionary patterns were adopted by different loop regions of mycoplasma enolase. Enolases from different Mycoplasma species also showed different affinities for PLG and fibronectin. Our results indicate the rapid and divergent evolution of mycoplasma enolase and mycoplasmas. This study will also aid understanding the independent evolution of Mycoplasma species after separation from their common ancestor.
Camellia oleifera, a woody plant that produces edible oil, is indigenous to China. The devastating disease of anthracnose inflicts significant financial losses on Ca. oleifera. The primary causative agent of anthracnose on Ca. oleifera is Colletotrichum fructicola. Chitin, a pivotal constituent of fungal cell walls, assumes a critical function in their proliferation and maturation. To study the biological functions of chitin synthase 1(Chs1) in C. fructicola, the CfCHS1 gene knockout mutants, ∆Cfchs1-1 and ∆Cfchs1-2, and their complementary strain, ∆Cfchs1/CfCHS1, of C. fructicola were generated. Our results showed that the colony diameters of wild-type and complement-strain ∆Cfchs1/CfCHS1, mutant ∆Cfchs1-1 and ∆Cfchs1-2 cultured on the CM and MM medium were 5.2, 5.0, 2.2 and 2.4 cm and 4.0, 4.0, 2.1 and 2.6 cm, respectively, which were significantly smaller for the mutant than for the wild type and complement strain; the inhibition rates on the CM medium supplemented with H2O2, DTT, SDS and CR were 87.0% and 88.5%, 29.6% and 27.1%, 88.0% and 89.4%, and 41.7% and 28.7%, respectively, for the mutant strains, ∆Cfchs1-1 and ∆Cfchs1-2, which were significantly higher than those for the other two strains; the rate of hyphal tips with CFW fluorescence in ∆Cfchs1-1 and ∆Cfchs1-2 was 13.3% and 15.0%, which was significantly lower than those for the other two strains; the mutant strains, ∆Cfchs1-1 and ∆Cfchs1-2, lost the ability to produce conidia; the mutant strains showed weaker pathogenicity on wounded and unwounded Ca. oleifera leaves than the wild type and complement strain. The findings of this study suggest that CfChs1 plays a crucial role in the growth and development, stress responses, and pathogenicity of C. fructicola. Thus, this gene could be a potential target for developing novel fungicide.
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