AN ELISA PROCEDURE FOR QUANTIFICATION OF RELATIVE AMOUNTS OF INTERCELLULAR GLYCOPROTEIN IN LEGUME NODULES

An enzyme-linked immunosorbant assay (ELISA) method based on a monoclonal antibody (MAC236) is described in which relative amounts of an intercellular glycoprotein were quantified in extracts of whole legume nodules. This glycoprotein has recently been shown to be an important component of the cortical oxygen diffusion barrier. The ELISA method is demonstrated on three examples of soybean (Glycine max L. Merr.) nodule systems which have been the subject of previously published investigations: (a), cv. Clarke inoculated with Brady rhizobium japonicum RCR3442, nodulated root systems of which were subject to 10, 21 or 40% oxygen continuously for 28 d; (b), cv. Bragg and its supernodulating mutant derivative (nts382) inoculated with Bradyrhizobium japonicum USDA110; (c), cv. Clarke inoculated with Bradyrhizobium japonicum RCR3442 or RCR3407. ELISA results are related to oxygen diffusion characteristics defined in previous publications and show that increases in the amount of glycoprotein present correlated with increases in supra-ambient (40%) levels of rhizosphere pOa, in minimum gas diffusion resistance and in speed of diffusion barrier response. Area data of component parts of nodule inner cortices suggest that diffusion resistance control under sub-ambient (10%) oxygen levels also involves cell expansion. The amount of MAC236 antigen in nodules is affected by both host plant genotype and rhizobial strain and the latter also appears to be involved in determining the morphological development of the nodule inner cortex. © 1993 Annals of Botany Company.