Dendrobiumorchids contain an inducer ofAgrobacteriumvirulence genes

SuccessfulAgrobacterium-mediated transformation of monocots such as orchids hinges on the induction of virulence(vir)genes in the bacterium, an event that is required for the activation of the T-DNA processing and transfer pathway. In dicots, several plant phenolic compounds, for example acetosyringone, coumaryl alcohol and sinapyl alcohol, are knownvirgene inducers, but in monocots their presence and characteristics are not well established. We report herein the presence and identification of coniferyl alcohol as thevirgene inducer in the monocotDendrobium.At an early stage of development as protocorm-like bodies (PLBs), this orchid contains an aryl β-glycoside, similar to coniferin, whose aglycone moiety is coniferyl alcohol. Coniferyl alcohol is elaborated in high amounts from PLBs and its production or stability is enhanced almost six-fold higher when the PLBs were exposed to light than when maintained in the dark. PLBs produced 11-fold more inducer than leaves. These studies show for the first time that orchids, i.e.Dendrobium,exude coniferyl alcohol as avirgene inducer.