Effect of TOR Inhibitor Rapamycin on Growth, Development, and Autophagy of Peronophythora litchii

  Objective  Effects of the target of rapamycin (TOR) inhibitor rapamycin on the growth, development, pathogenicity, and autophagy of Peronophythora litchi were studied.

  Method  The mycelial growth, sporangial production, zoospore release, and pathogenicity of the P. litchi after being treated by the TOR inhibitor rapanmycin in varying concentrations were determined, while the mycelial autophagy observed under a microscope with MDC staining.

  Result  Rapamycin exhibited significant inhibitory effect on the mycelial growth of P. litchii with an EC₅₀ value of 29.18 ng·mL⁻¹ and varying extents of increases with higher dosages. When treated with 25.0 ng·mL⁻¹ rapamycin, the inhibition rate was 45.3% and the sporulation at 8.0×10⁴ sporangia·mL⁻¹ (which was 27.9% of control), while the zoospore release increased, but the virulence of P. litchii significantly reduced. The MDC-stained autophagosomes significantly increased as well.

  Conclusion   The TOR signaling pathway inhibitor rapamycin played an important role in the mycelial growth, development, and virulence of P. litchii.