Cytokinins as key regulators in plant-microbe-insect interactions: connecting plant growth and defence
Résumé
Plants constitute key nutritional resources for many organisms on Earth and therefore interact with multiple biotic partners ranging from antagonists to mutualists. Plants are under selection pressure to enhance interactions with mutualists while reducing interactions with antagonists. As allocation strategies are constrained by a limiting pool of nutrients, plants are faced with a trade-off between allocation of resources to growth versus defence (Herms & Mattson 1992). In this context, it is interesting to see that plant growth and defence can be regulated by similar phytohormones (Fig. 1). Various community members can contribute to plant growth, while others attack plants and need to be countered by effective defences that may be induced by the attackers. Interactions of plants with members of their ecological community, once perceived by the plant, can lead to a profound metabolic reconfiguration of the plant physiology, which favours beneficial organisms and deters antagonists like pathogens or herbivores (e.g. Kessler & Baldwin 2002; Pieterse & Dicke 2007; Schwachtje & Baldwin 2008). For instance, under pathogen infection and