Cellular expression pattern of the glycine decarboxylase P protein in leaves of an intergeneric hybrid between the C3-C4 intermediate species Moricandia nitens and the C3 species Brassica napus

An intergeneric hybrid plant was produced between the C3-C4 intermediate species Moricandia nitens and the C3 species Brassica napus by sexual hybridization and in vitro embryo rescue. The hybrid nature of the plant was apparent in its morphology and flower pigmentation and was confirmed by leaf isozyme patterns. The overall plant morphology and the shape and thickness of leaves of the hybrid plant were intermediate between those of the parent species. However, the bundle-sheath cells of the hybrid resembled those of the C3 parent and lacked the organelle development of the C3-C4 intermediate parent. Immunogold labelling for the presence of the P subunit of the mitochondrial glycine decarboxylase complex revealed a very similar labelling density on mitochondria in bundle-sheath and mesophyll cells in B. napus, while in M. nitens the P subunit was only detectable in bundle sheath cells. In the hybrid the labelling density on mesophyll cell mitochondria was almost half of that on the bundle-sheath mitochondria. The CO2 compensation point of the hybrid was significantly less than that of the C3 parent but was not as low, nor as responsive to changes in light intensity, as for the C3-C4 parent.