Regulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase by wounding and methyl jasmonate - Implications for the production of anti-cancer alkaloids

HMGR (3-hydroxy-3-methylglutaryl-coenzyme A reductase; E.C.1.1.1.34) supplies mevalonate for the synthesis of many plant primary and secondary metabolites, including the terpenoid component of indole alkaloids. Suspension cultures of Camptotheca acuminata and Catharanthus roseus, two species valued for their anticancer indole alkaloids, were treated with the elicitation signal transducer methyl jasmonate (MeJA). RNA gel blot analysis from MeJA treated cultures showed a transient suppression of HMGR mRNA, followed by an induction in HMGR message. Leaf disks from transgenic tobacco plants containing a chimeric hmgl::GUS construct were also treated with MeJA and showed a dose dependent suppression of wound-inducible GUS activity. The suppression of the wound response by MeJA was limited to the first 4 h post-wounding, after which time MeJA application had no effect. The results are discussed in relation to the differential regulation of HMGR isogenes in higher plants.