Hahn M G, Bonhoff A, Grisebach H
Lehrstuhl für Biochemie der Pflanzen, Biologisches Institut II der Universität Freiburg, Schänzlestrasse 1, D-7800 Freiburg im Breisgau, Federal Republic of Germany.
Plant Physiol. 1985 Mar;77(3):591-601. doi: 10.1104/pp.77.3.591.
A radioimmunoassay specific for glyceollin I was used to quantitate this phytoalexin in roots of soybean (Glycine max [L.] Merr. cv Harosoy 63) after infection with zoospores of either race 1 (incompatible) or race 3 (compatible) of Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin. The sensitivity of the radioimmunoassay and an inmmunofluorescent stain for hyphae permitted quantitation of phytoalexin and localization of the fungus in alternate serial cryotome sections from the same root. The incompatible interaction was characterized by extensive fungal colonization of the root cortex which was limited to the immediate vicinity of the inoculation site. Glyceollin I was first detected in extracts of whole roots 2 hours after infection, and phytoalexin content rose rapidly thereafter. Significant concentrations of glyceollin I were present at the infection site in cross-sections (42 micrometers thick) of such roots by 5 hours, and exceeded 0.6 micromoles per milliliter (EC(90)in vitro for glyceollin I) by 8 hours after infection. Longitudinal sectioning (14 micrometers thick) showed that glyceollin I accumulated particularly in the epidermal cell layers, but also was present in the root cortex at inhibitory concentrations. No hyphae were observed in advance of detectable levels of the phytoalexin and, in most roots, glyceollin I concentrations dropped sharply at the leading edge of the infection. In contrast, the compatible interaction was characterized by extensive unchecked fungal colonization of the root stele, with lesser growth in the rest of the root. Only small amounts of glyceollin I were detected in whole root extracts during the first 14 hours after infection. Measurable amounts of glyceollin I were detected only in occasional cross-sections of such roots 11 and 14 hours after infection. The phytoalexin was present at inhibitory concentrations in the epidermal cell layers, but the inhibitory zone did not extend appreciably into the cortex. Altogether, these data support the hypothesis that the accumulation of glyceollin I is an important early response of soybean roots to infection by P. megasperma, but may not be solely responsible for inhibition of fungal growth in the resistant response.
采用一种针对大豆抗毒素Ⅰ的放射免疫分析法，对感染了大豆疫霉（Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin）1号生理小种（不亲和）或3号生理小种（亲和）游动孢子的大豆（Glycine max [L.] Merr. cv Harosoy 63）根系中的这种植物抗毒素进行定量分析。放射免疫分析法的灵敏度以及针对菌丝的免疫荧光染色，使得能够对植物抗毒素进行定量分析，并在来自同一根系的交替连续冷冻切片中定位真菌。不亲和互作的特征是，根皮层中真菌大量定殖，但仅限于接种部位的紧邻区域。感染后2小时，在整个根系提取物中首次检测到大豆抗毒素Ⅰ，此后植物抗毒素含量迅速上升。到感染后5小时，在这种根系的横切面（42微米厚）的感染部位存在显著浓度的大豆抗毒素Ⅰ，感染后8小时超过每毫升0.6微摩尔（大豆抗毒素Ⅰ的体外EC(90)）。纵切（14微米厚）显示，大豆抗毒素Ⅰ尤其在表皮细胞层积累，但在根皮层中也以抑制浓度存在。在可检测到植物抗毒素水平之前未观察到菌丝，并且在大多数根系中，大豆抗毒素Ⅰ浓度在感染前沿急剧下降。相比之下，亲和互作的特征是根中柱中真菌大量定殖且不受抑制，而根的其余部分生长较少。感染后最初14小时内，在整个根系提取物中仅检测到少量大豆抗毒素Ⅰ。仅在感染后11小时和14小时的此类根系的偶尔横切面上检测到可测量量的大豆抗毒素Ⅰ。植物抗毒素在表皮细胞层中以抑制浓度存在，但抑制区并未明显延伸到皮层。总之，这些数据支持这样的假说，即大豆抗毒素Ⅰ的积累是大豆根系对大豆疫霉感染的重要早期反应，但可能并非抗性反应中抑制真菌生长的唯一原因。
