Immunocytochemical localization of NAD‐dependent glyceraldehyde‐3‐phosphate dehydrogenase in soybean nodules

Polyclonal antibodies raised against NAD‐dependent glyceraldehyde‐3‐phosphate dehydrogenase (D‐glyceraldehyde‐3‐phosphate:NAD+ oxidoreductase [phosphorylating], EC 1.2.1.12) from the plant cytosolic fraction of soybean [Glycine max (L.) Merr. cv. Williams] nodules were used to study the subcellular location of the enzyme and its relative distribution between infected, interstitial and cortical cells of soybean (cv. Lincoln) nodules. Post‐embedding immunogold labelling was carried out on nodules harvested 5, 12, 19 and 25 days after the first sign of nodulation. Labelling for glyceraldehyde‐3‐phosphate dehydrogenase was observed over the cytoplasm and nuclei of infected and uninfected cells, as well as over the nucleoid regions of bacteroids. In 5‐day‐old nodules, label also bound adjacent to the peribacteroid membranes. Statistical analysis of the number of gold particles per cell area indicated that in 5‐day‐old nodules, glyceraldehyde‐3‐phosphate dehydrogenase was distributed equally between infected, interstitial and cortical cells, but in older nodules the enzyme was more prominent in the interstitial and cortical cells than in infected cells.