Cytology And Biochemical Properties Of The 67 KDa Vegetative Storage Protein In Hevea Brasiliensis Muell. Arg.

Recently, Chrestin et al., considered that the P66, a protein which distributed specifically in the inner bark, was related to bark necrosis. We thought that the P66 was just the 67 kDa vegetative storage protein (VSP) we had ever reported. For the purpose of elucidating its biological roles, we investigated, in this paper, that subcellular localization and biochemical properties of the 67 kDa VSP by using colloid gold labelling, chromatograph, SDS-PAGE, Western-blot, two-dimensional electrophoresis and RT-PCR techniques. The 67 kDa VSP sequestered uniquely in the large central vacuoles of protein-storing cells. It distributed in virgin trees, tapping healthy trees, the tapped healthy trees that were on rest and TPD(tapping panel dryness) trees that had not been exploited for several years, among which the protein was much richer in the later two. RT-PCR analysis showed that the content of the 67 kDa VSP was associated with the extent of its gene expression. The 67 kDa VSP is acidic with a pI of 6.10. The protein possessed both glucosidase activity and linamarase activity and characterized as a cyanogenicβ-glucosidase. And moreover, the 67 kDa VSP shared 97.7% identity with the P66 protein that was considered to be related to TPD(or bark necrosis). Taken together, we suggest that the 67 kDa VSP and the P66 protein are the natural variates of the same protein and have nothing to do with TPD or bark necrosis. Otherwise, the 67 kDa VSP may have a role in protecting panel in addition to nitrogen storage.