The information landscape of plant constitutive and induced secondary metabolite production

• Function and evolution of inducibility of resistance still remain unclear.
• Most basic function of plant secondary metabolite production is information transfer.
• Constitutive production of secondary metabolites determines herbivore host choice.
• Inducibility: plants can use expanded interaction arena to cope with herbivore attack.

Resistance against antagonist organisms, such as herbivores, has been identified as a major function of constitutive and stress-inducible production of plant secondary metabolites (PSMs). The mechanism through which constitutive expression and inducibility mediate resistance and, hence physiological and ecological factors that affect their evolution are still little understood. Here I propose information transfer as the least common denominator function of PSM production. In this framework constitutively produced PSMs represent the first line of defense through functioning as toxins, cues associated with toxicity and as detractants that interfere with antagonist host-search patterns. Information made available and utilizable by inducibility of secondary metabolite production allows plants to include the associated biological communities to cope with antagonists and to more efficiently target a specific attacker.