Euphorbia latex biochemistry: complex interactions in a complex environment

Plant latex is a complex environment. Occurring in hundreds of plant species and contained in a tube system called laticifers, latex is a milky sap with a diverse composition that includes alkaloids, terpenoid compounds, other secondary metabolites and a number of enzymes. These substances are collectively believed to provide an important contribution to plant defence mechanisms by repelling and killing phytopathogens, and sealing wounded areas. This review provides insights of what is currently known about the biochemistry and molecular biology of plant latex, as studied in various model systems, above all the economically important rubber tree, Hevea brasiliensis. Selecting the Mediterranean shrub Euphorbia characias as a complementary experimental model, we have recently begun to disclose the properties of several components of the enzymatic machinery present in its latex. Although the scheme of multi-enzymatic interactions taking place in the E. characias latex depicted to date is certainly incomplete, the emerging scenario suggests that the role played by latex in plants might be significantly less passive than previously believed.