Periploca sepium Bunge as a Model Plant for Rubber Biosynthesis Study

Periploca sepium Bunge (Chinese silk vine) is a woody climbing vine belonging to the family Asclepiadaceae. It originally comes from Northwest China. Periploca resembles the Para-rubber tree, Hevea brasiliensis, regarding a similar body plan to produce a milky exudate containing rubber latex. The Periploca plant was assessed as a rubber-producing plant by rubber structure elucidation and its molecular weight distribution. A rubber fraction purified from the milky exudate was subjected to 1H NMR analysis, and a characteristic signal derived from cis-polyisoprene was observed. In addition, when the molecular weight distribution of rubber components in the exudate was measured (using size-exclusion chromatography), the number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity (Mw/Mn) were estimated to be Mn = 1.3 × 105, Mw = 4.1 × 105, and Mw/Mn = 3.1, respectively. Furthermore, the presence of polyisoprene, with Mn = 4.0 × 104, Mw = 7.6 × 104, and Mw/Mn = 2.5, was also confirmed in plantlets obtained from shoots as a result of tissue culture