Towards a latex molecular diagnostic of yield potential and the genetic engineering of the rubber tree

The latex from Hevea brasiliensis is expelled from specialized cells upon bark tapping. The latex yield is mainly limited by the duration of the latex flow, which is controlled by coagulation processes. Bark treatment with ethylene is known to delay coagulation and increase latex yield. The molecular basis of latex coagulation has been characterized: (1) Hevein, a lectin-like protein, induces latex coagulation by bringing together the rubber particles (RPs). The hevein-RPs bridging is mediated by N-Acetyl-D-glucosamine, and involves a 22 kDa receptor glycoprotein localized on the RPs surface. This process is inhibited by the removal of the sugar moiety from the receptor, through the action of N-acetyl-glucosaminidase and chitinases. (2) Ethylene induces, in the latex cells, an over-expression of the 3 genes coding for hevein and its receptor, and a chitinase. The higher over-expression of one chitinase can explain the partial deglycosylation of the hevein receptor and the resulting delay in coagulation. (3) The level of hevein and chitinase expression in the latex is a clonal characteristic, linked to the characteristics of the latex flow. Expression of these genes might be used as molecular markers for high yield potential. Based on these findings, it would be interesting to improve the rubber tree through the genetic engineering technics, to get new high yielding cultivars with prolonged latex flow. This revised version was published online in July 2006 with corrections to the Cover Date.