Helping plants to deal with insects: the role of beneficial soil-borne microbes

Several soil-borne microbes such as mycorrhizal fungi and plant growth-promoting rhizobacteria can help plants to deal with biotic and abiotic stresses via plant growth promotion and induced resistance. Such beneficial belowground microbes interact in a bidirectional way via the plant with aboveground insects such as herbivores, their natural enemies and pollinators. The role of these interactions in natural and agricultural ecosystems is receiving increased attention, and the molecular and physiological mechanisms involved in these interactions should be the focus of more attention. Here, we review the recent discoveries on plant-mediated interactions between beneficial belowground microbes and aboveground insects. Several soil-borne microbes such as mycorrhizal fungi and plant growth-promoting rhizobacteria can help plants to deal with biotic and abiotic stresses via plant growth promotion and induced resistance. Such beneficial belowground microbes interact in a bidirectional way via the plant with aboveground insects such as herbivores, their natural enemies and pollinators. The role of these interactions in natural and agricultural ecosystems is receiving increased attention, and the molecular and physiological mechanisms involved in these interactions should be the focus of more attention. Here, we review the recent discoveries on plant-mediated interactions between beneficial belowground microbes and aboveground insects. insects (e.g. caterpillars) that have chewing mouthparts and feed on plant tissue, removing pieces of tissues. microbe that colonises the rhizosphere and that provides a benefit to the plant, such as enhancing plant growth, inducing resistance or directly neutralising detrimental organisms. plant characteristics that negatively affect the performance of herbivorous insects, such as toxins or thorns, and thereby enhance the fitness of the plant. plant characteristics that improve the effectiveness of natural enemies of herbivores, for example through provision of shelter, alternative food or infochemicals, and thereby enhance the fitness of the plant. enhanced resistance of a plant against detrimental organisms, induced by non-pathogenic soil-borne microbes such as plant growth-promoting rhizobacteria and fungi. insects (e.g. aphids and whiteflies) that feed on phloem sap with mouthparts modified into a sucking stylet. endogenous secondary metabolites such as jasmonic acid or abscisic acid that regulate physiological processes in the plant such as defence and growth. change in physiological state that allows the plant to activate defence responses faster and stronger against different attackers, and that can be elicited by living organisms and synthetic compounds. space around plant roots containing a high density of microbes, directly influenced by both roots and microbes.