graminearum homolog of A. nidulansApsB. The functions of FgApsB were evaluated by constructing a deletion mutant of FgApsB, designated ΔFgApsB-28. Conidiation and mycelial growth rate are reduced in ΔFgApsB-28. The hyphae of ΔFgApsB-28 are thinner than those of the wild type and have a
different branching angle. ΔFgApsB-28 exhibited reduced aerial hyphae formation, but increased production of rubrofusarin. Whereas nuclei are evenly distributed in germ tubes and hyphae of the wild type, they are clustered and irregularly distributed in ΔFgApsB-28. The mutant exhibited increased resistance to cell wall-damaging agents, but reduced virulence on flowering wheat heads, which MK-2206 solubility dmso is consistent with its reduced production of the toxin deoxynivalenol. All of the defects in ΔFgApsB-28 were restored by genetic complementation with the parental FgApsB gene. Taken together, the results indicate
that FgApsB is important for vegetative differentiation, asexual development, nuclear migration, and virulence in F. graminearum. “
“The formation of nonspecific ion channels by small oligomeric amyloid intermediates is toxic to the host’s cellular membranes. Thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) are major virulence factors of Vibrio parahaemolyticus. We have previously reported the MAPK inhibitor crystal structure of TDH tetramer with the central channel. We have also identified the molecular mechanism underlying the paradoxical responses to heat treatment of TDH, known as the Arrhenius PRKD3 effect, which is the reversible amyloidogenic property. In the present report, we describe the biophysical properties of TRH, which displays 67% amino acid similarity with TDH. Molecular modeling provided a good fit of the overall structure of TDH and TRH. Size-exclusion chromatography, ultracentrifugation, and transmission electron microscopy revealed that TRH formed tetramer in solution. These toxins showed similar hemolytic activity on red blood cells. However, TRH had less amyloid-like structure than TDH analyzed by thioflavin T-binding assay
and far-UV circular dichroism spectra. These data indicated that amyloidogenicity upon heating is not essential for the membrane disruption of erythrocytes, but the maintenance of tetrameric structure is indispensable for the hemolytic activity of the TDH and TRH. Vibrio parahaemolyticus is a gram-negative marine bacterium recognized as a major cause of seafood-borne gastroenteritis around the world. Wound infections, septicemia, and other infections are also caused occasionally by V. parahaemolyticus outbreaks (Blake et al., 1980; Daniels et al., 2000). Thermostable direct hemolysin (TDH) and its homolog TRH are the major virulence factors of this microorganism (Honda et al., 1980, 1988; Joseph et al., 1982; Shirai et al., 1990).