Characterization of natural rubber biosynthesis in Ficus benghalensis

Natural rubber was identified for the first time in the latex of Ficus beng halensis, and the rubber biosynthetic activity in latex and rubber particle s was investigated. C-13 NMR analysis of samples prepared by successive ext ractions with acetone and benzene confirmed that the benzene-soluble residu es were natural rubber, cis-1,4-polyisoprene. The rubber content in the lat ex of F. benghalensis was approximately 17 %. Gel permeation chromatography revealed that the molecular mass of the natural rubber from F: benghalensi s was approximately 1500 kDa. The high rubber content and large molecular s ize suggest that F. benghalensis is a good candidate for an alternative rub ber source. Examination of latex serum from F. benghalensis by SDS-polyacry lamide gel electrophoresis revealed a small number of proteins with major p roteins of 31 and 55 kDa in size. The 31-kDa protein was predominant in cat alytically-active rubber particles. Determination of metal ion concentratio n in latex and a comparison of the effect of ethylenediamine-tetraacetic ac id on in vitro rubber biosynthesis in F. benghalensis, F. carica and Hevea brasiliensis suggest that the divalent metal ion present in latex serum is an important physiological factor controlling the rubber biosynthetic activ ities in these plant species. Microscopic examination revealed that the rub ber in F. benghalensis occurred in a series of laticifer cells located in c oncentric zones in the inner bark of stems and branches. (C) 2000 Editions scientifiques et medicales Elsevier SAS.