Howard R J, Ferrari M A, Roach D H, Money N P
Central Research and Development, DuPont Company, Wilmington, DE 19880-0402.
Proc Natl Acad Sci U S A. 1991 Dec 15;88(24):11281-4. doi: 10.1073/pnas.88.24.11281.
Many fungal pathogens penetrate plant leaves from a specialized cell called an appressorium. The rice blast pathogen Magnaporthe grisea can also penetrate synthetic surfaces such as poly(vinyl chloride). Previous experiments have suggested that penetration requires an elevated appressorial turgor pressure. In the present report we have used nonbiodegradable Mylar membranes, exhibiting a range of surface hardness, to test the proposition that penetration is driven by turgor. Reducing appressorial turgor by osmotic stress inhibited penetration of these membranes. The size of the turgor deficit required to inhibit penetration was a function of the surface hardness. Penetration of the hardest membranes was inhibited by small decreases in appressorial turgor, while penetration of the softer membranes was sensitive only to large decreases in turgor. Similarly, penetration of the host surface was inhibited in a manner comparable to penetration of the hardest Mylar membranes. Indirect measurements of turgor, obtained through osmotically induced collapse of appressoria, indicated that the infection apparatus can generate turgor pressures in excess of 8.0 MPa (80 bars). We conclude that penetration of synthetic membranes, and host epidermal cells, is accomplished by application of the physical force derived from appressorial turgor.
许多真菌病原体通过一种称为附着胞的特殊细胞穿透植物叶片。稻瘟病菌也能穿透诸如聚氯乙烯之类的合成表面。先前的实验表明，穿透需要附着胞内升高的膨压。在本报告中，我们使用了具有一系列表面硬度的不可生物降解的聚酯薄膜来测试穿透是由膨压驱动这一命题。通过渗透胁迫降低附着胞膨压会抑制这些薄膜的穿透。抑制穿透所需的膨压亏缺大小是表面硬度的函数。附着胞膨压的小幅降低就能抑制最硬薄膜的穿透，而较软薄膜的穿透仅对膨压的大幅降低敏感。同样，寄主表面的穿透也以与最硬聚酯薄膜穿透相当的方式受到抑制。通过渗透诱导附着胞塌陷获得的膨压间接测量表明，侵染机构能产生超过8.0兆帕（80巴）的膨压。我们得出结论，合成膜和寄主表皮细胞的穿透是通过施加源自附着胞膨压的物理力来完成的。
