Abstract
We investigate function of nucleotide pyrophosphatase/phosphodiesterase (NPP) gene family in rice (Oryza sativa L.). Six genes of NPP homologues are existed and located on chromosomes 3 (NPP3), 8 (NPP1), 9 (NPP6) and 12 (NPP2, 4, 5). Recombinant proteins for NPP1, 2 and 6 were expressed and purified from transgenic rice cells. Computer-assisted analyses showed that the deduced amino-acid sequences contain numerous N-glycosylation sites and cleavable hydrophobic signal sequences. All NPP1, 2 and 6 proteins actually conatined N-linked oligosaccharide chains recognized by Con A and Endo-H. However, confocal laser scanning microscopy of rice cells expressing NPP1-GFP, NPP2-GFP and NPP6-GFP revealed that they similarly localize in the chroloplast compartment. The results obtained suggest that the NPP family is synthesized and transported from ER-Golgi system to plastids, and possibly involved in the control of plastidial levels of nucleotides linked to glycosylation.
