Abundant microfibrillar protein inclusions were present in the lutoids of the primary laticifers in Hevea brasiliensis Mull. Arg. Two forms of the inclusions could be distinguished under the electron microscope, each in separate lutoids. As revealed by SDS-PAGE, the 59.5 kD and 63.5 kD proteins were the major components of the microfibrillar protein purified by isoeleettic point precipitation. Western-blotting analysis indicated that they were immunorelated with the 67 kD protein accumulated in the protein-storing cells. The 59.5 kD and 63.5 kD proteins were abundant in the uppermost part, the stem of new shoot and sustained their abundance during the growth and development of new shoot while their contents decreased remarkably in the lower parts of the trunk, accompanying by the accumulation of 3-5 kinds of proteins with low molecular weights. This fluctuating pattern suggested that the degradation of the 59.5 kD and 63.5 kD proteins had nothing to do with the new shoot growth and may be closely related to the primary laticifer differentiation. The 67 kD protein could not be detected in the young stem of new shoot when its leaves were broze-colored while the protein started to be accumulated in the stem, when the leaves of new shoot had matured, behaving like a typical vegetative storage protein.
