Intercellular location of glycoprotein in soybean nodules: effect of altered rhizosphere oxygen concentration
Abstract. A glycoprotein which occludes intercellular spaces in the inner cortex of legume nodules may be involved in controlling oxygen diffusion into rhizobial-infected cells. Here we investigated this possibility by localizing the glycoprotein using monoclonal antibodies and immunogold labelling in nodulated roots of soybean cv. Clarke inoculated with Bradyrhizobium japonicum strain RCR3442 exposed to atmospheres with either 10, 21 (control) or 40% oxygen for 28d. Infected cells showed evidence of premature senescence when grown in above or below ambient pO2 particularly at 10% oxygen, although cortical cells appeared to be little altered by oxygen treatment. In the inner cortical cells, more glycoprotein was seen to be occluding intercellular spaces of those nodules subjected to 40% oxygen and less in those nodules exposed to 10% oxygen, when compared to controls. This observation, made at the light microscope level (using silver enhancement) was confirmed under the TEM using immunogold labelling. Therefore, it is suggested that intercellular space glycoprotein is one of the structural components of the diffusion resistance in the cortex of legume nodules.