Immunofluorescent localization of phosphoenolpyruvate carboxylase and ribulose 1,5-bisphosphate carboxylase/oxygenase proteins in leaves of C3, C 4 and C 3-C 4 intermediate Flaveria species.

An indirect immunofluorescence technique was used to determine the intercellular compartmentation of phosphoenolpyruvate (PEP) carboxylase and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) proteins in leaves of five species of Flaveria, F. brownii A.M. Powell (C4), F. cronquistii A.M. Powell (C3), F. linearis Lag. (C3-C4 intermediate), F. floridana J.R. Johnston (C3-C4) and F. chloraefolia A. Gray (C3-C4). The results were compared with representative C3 and C4 plants. No strict intercellular compartmentation of either enzyme was observed in any of the five Flaveria species examined. Both carboxylase proteins were found throughout the leaf chlorenchyma of the C3 Flaveria, as was also the case in Nicotiana tabacum L. (C3). A similar distribution pattern was observed not only in the three C3-C4 intermediates, but in the C4 Flaveria as well. This distribution contrasted markedly with the localization patterns found in Zea mays L. (C4), where Rubisco was confined to bundle-sheath chloroplasts and PEP carboxylase to the mesophyll cytoplasm.