The micromorphology and protein characterization of rubber particles in Ficus carica, Ficus benghalensis and Hevea brasiliensis

Abstract

Rubber biosynthesis takes place on the surface of rubber particles. These particles are surrounded by a monolayer membrane in which the rubber transferase is anchored. In order to gain better insight into whether rubber particles from different plant species share common structural characteristics, the micromorphology of rubber particles from Ficus carica, Ficus benghalensis, and Hevea brasiliensis was examined by electron microscopy. Rubber particles of all three species were spherical in shape, and the size of rubber particles of H. brasiliensis was much smaller than those of F. carica and F. benghalensis. In addition, investigations were undertaken to compare the cross-reactivity of the antibody raised against either the H. brasiliensis small rubber particle protein (SRPP) which is suggested to be involved in rubber biosynthesis, or the cis-prenyltransferase (CPT) which has an activity similar to rubber transferase. Both western analysis and TEM-immunogold labelling studies showed that rubber particles of F. carica and F. benghalensis do not contain the SRPP. None of the rubber particles in F. carica, F. benghalensis and H. brasiliensis contained the CPT, suggesting that the CPT itself could not catalyse the formation of high molecular weight rubber. These results indicate that rubber particles in the three different plant species investigated share some degree of similarity in architecture, and that the SRPP and CPT themselves are not the core proteins necessary for rubber biosynthesis.

Identification of a New Class of Lipid Droplet-Associated Proteins in Plants

“…For instance, rubber particles isolated from Ficus carica and Ficus benghalensis did not contain SRPP proteins that cross reacted with rubber tree SRPP antisera, despite their ability to produce significant amounts of rubber (Singh et al, 2003). Russian dandelion, on the other hand, contains five SRPP-like genes, but only three of the encoded proteins have been detected in high amounts in purified rubber particles, and one of the genes shows a distinct organ and temporal gene expression pattern that is inconsistent with a role in rubber synthesis (Schmidt et al, 2010).…”

Histochemical study of detailed laticifer structure and rubber biosynthesis-related protein localization in Hevea brasiliensis using spectral confocal laser scanning microscopy

“…In H. brasiliensis, they have bimodal size distribution in fresh latex. Large rubber particles (LRPs) and small rubber particles (SRPs) show diVerences not only in molecular weight distribution and molecular structure but also in their surface proteins (Bahri and Hamzah 1996;Sakdapipanich et al 1999;Ohya et al 2000;Singh et al 2003;Tarachiwin et al 2005). Immunogold electron microscopy has shown that 14-and 24-kDa proteins are localized abundantly on LRPs and SRPs, respectively (Bahri and Hamzah 1996;Singh et al 2003).…”

“…Large rubber particles (LRPs) and small rubber particles (SRPs) show diVerences not only in molecular weight distribution and molecular structure but also in their surface proteins (Bahri and Hamzah 1996;Sakdapipanich et al 1999;Ohya et al 2000;Singh et al 2003;Tarachiwin et al 2005). Immunogold electron microscopy has shown that 14-and 24-kDa proteins are localized abundantly on LRPs and SRPs, respectively (Bahri and Hamzah 1996;Singh et al 2003). Coding genes of 14 kDa rubber elongation factor (REF) and 24 kDa SRP protein (SRPP) have been cloned (Attanyaka et al 1991;Goyvaerts et al 1991;Oh et al 1999).…”

Natural Rubber Biosynthesis and Physic-Chemical Studies on Plant Derived Latex

“…A positive effect was observed when small rubber particle protein (SRPP) and rubber elongation factor (REF), both proteins belonging to the REF superfamily, were added to washed rubber particles in H. brasiliensis (Oh et al, 1999;Wititsuwannnakul et al, 2003). As shown by immunogold labeling SRPPs are the most abundant proteins on rubber particles in H. brasiliensis (Oh et al, 1999;Singh et al, 2003;Sando et al, 2009). Other factors have not been identified as crucial for rubber biosynthesis so far.…”

“…These data suggest that the rubber transferase might indeed be a CPT. However, immunogold labeling of rubber particles from H. brasiliensis using an antibody raised against a synthetic peptide with a consensus sequence for a highly conserved region of CPTs failed to detect CPTs on rubber particles and unlike CPTs, the rubber transferase does not synthesize products of predetermined size but can synthesize products of a wide range of molecular mass (Castillion and Cornish, 1999;Singh et al, 2003;da Costa et al, 2005). However, the varying size of the natural rubber product was shown not to be solely dependant on the rubber transferase.…”