IMMUNOGOLD LOCALIZATION OF RIBULOSE-1,5-BISPHOSPHATE CARBOXYLASE/OXYGENASE AND GLYCINE DECARBOXYLASE IN THE NONCLASSICAL C4 SPECIES ARISTIDA-FUNICULATA

The distribution of the carboxylating enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and an enzyme of the photorespiratory pathway (glycine decarboxylase) was determined within the leaf tissue by immunocytochemical techniques in C3, C4 and C3:C4 intermediate species. The specificity of the method for all the material was demonstrated by sodium dodecyl sulphate acrylamide gels and Western blotting of crude protein extracts. In the C3 species (wheat) the enzymes were located in chloroplasts (RuBPCO) and mitochondria (glycine decarboxylase) of mesophyll cells, while in the three ''classical'' C4 standards, i.e. Zea mays (''NADP-ME'' type), Panicum maximum (''PCK'' type) and P. turgidum (''NAD-ME'' type), these were found exclusively in the respective organelles of the bundle sheath. In the intermediate species, RuBPCO was not compartmented as it was located in chloroplasts of mesophyll and bundle sheath cells. Yet glycine decarboxylase was found exclusively in bundle sheath mitochondria. In Aristida funiculata, a C4 species with ''non-classical'' leaf structure, RuBPCO was found in chloroplasts of both the inner and outer bundle sheaths and glycine decarboxylase was located exclusively in mitochondria of the inner bundle sheath cells. It is suggested that A. funiculata may be a C4 species with C3:C4-like intermediate characteristics based on the observed distribution of glycine decarboxylase, although gas-exchange characteristics of this species are required before any reclassification can be considered.