Dazzo F B, Orgambide G G, Philip-Hollingsworth S, Hollingsworth R I, Ninke K O, Salzwedel J L
Department of Microbiology, Michigan State University, East Lansing 48824, USA.
J Bacteriol. 1996 Jun;178(12):3621-7. doi: 10.1128/jb.178.12.3621-3627.1996.
We used bright-field, time-lapse video, cross-polarized, phase-contrast, and fluorescence microscopies to examine the influence of isolated chitolipooligosaccharides (CLOSs) from wild-type Rhizobium leguminosarum bv. trifolii on development of white clover root hairs, and the role of these bioactive glycolipids in primary host infection. CLOS action caused a threefold increase in the differentiation of root epidermal cells into root hairs. At maturity, root hairs were significantly longer because of an extended period of active elongation without a change in the elongation rate itself. Time-series image analysis showed that the morphological basis of CLOS-induced root hair deformation is a redirection of tip growth displaced from the medial axis as previously predicted. Further studies showed several newly described infection-related root hair responses to CLOSs, including the localized disruption of the normal crystallinity in cell wall architecture and the induction of new infection sites. The application of CLOS also enabled a NodC- mutant of R. leguminosarum bv. trifolii to progress further in the infection process by inducing bright refractile spot modifications of the deformed root hair walls. However, CLOSs did not rescue the ability of the NodC- mutant to induce marked curlings or infection threads within root hairs. These results indicate that CLOS Nod factors elicit several host responses that modulate the growth dynamics and symbiont infectibility of white clover root hairs but that CLOSs alone are not sufficient to permit successful entry of the bacteria into root hairs during primary host infection in the Rhizobium-clover symbiosis.
我们使用明场、延时视频、交叉偏振、相差和荧光显微镜技术，来研究从野生型三叶草根瘤菌中分离出的壳脂寡糖（CLOSs）对白三叶草根毛发育的影响，以及这些生物活性糖脂在宿主初次感染中的作用。CLOS的作用使根表皮细胞分化为根毛的数量增加了两倍。成熟时，根毛显著更长，这是因为活跃伸长的时间延长了，而伸长速率本身没有变化。时间序列图像分析表明，CLOS诱导根毛变形的形态学基础是如先前预测的那样，尖端生长从内侧轴发生了重新定向。进一步的研究显示了几种新描述的与感染相关的根毛对CLOSs的反应，包括细胞壁结构中正常结晶度的局部破坏以及新感染位点的诱导。CLOS的应用还使三叶草根瘤菌的NodC突变体在感染过程中能够进一步发展，方法是诱导变形根毛壁出现明亮的折射斑点变化。然而，CLOSs并不能挽救NodC突变体在根毛内诱导明显卷曲或感染线的能力。这些结果表明，CLOS结瘤因子引发了几种宿主反应，这些反应调节了白三叶草根毛的生长动态和共生体感染性，但在根瘤菌 - 三叶草共生关系中，仅CLOSs不足以使细菌在宿主初次感染期间成功进入根毛。
