The Role of Plant Hormones in Plant-Microbe Symbioses

This Research Topic explores the role of plant hormones in the regulation of beneficial symbioses established between plants and microbes. Since moving onto land, plants have evolved many strategies to assist in the acquisition of scare nutrient resources and also in the ability to cope with different biotic and abiotic stresses. One strategy has included the formation of beneficial plant-microbe symbioses. These relationships cover a whole range of microbial lifestyles, from associations with nitrogen-fixing bacteria (nodulation and actinorhizal associations), to partnering with nutrient-acquiring fungi (arbuscular mycorrhizae and ectomycorrhizae) to forming intimate relationships with other endosymbiotic microbes. The language that governs the complex dialogue enabling plants to recognize the symbiotic partner, accommodate the microbe within the plant tissue, regulate the extent of colonization, and derive benefit from the association is now emerging. Plant hormones are an important class of plant-derived compounds that control this dialogue by manipulating and monitoring all aspects of symbiosis from microbial recognition through to establishment of a functional, mutualistic symbiosis. There are many gaps in our knowledge, however, concerning how plant hormones mechanistically control symbiotic relationships. This is especially true as it relates to our understanding of how hormones are involved in the physical rearrangement of plant tissues during colonization, in how they may modulate nutrient trading during symbiosis, in how they regulate the extent of infection and, finally, in understanding how hormones may mitigate and/or amplify the negative effects of abiotic stress.

The current Research Topic welcomes manuscripts examining the role that plant hormones (abscisic acid, auxins, brassinosteroids, cytokinins, ethylene, gibberellins, jasmonic acid, salicylic acid and strigolactones) play in beneficial plant-microbe interactions. In particular, research that examines their roles in controlling uptake and hosting of symbiont, such as plant cellular re-modelling, as well as on how hormones regulate nutrient flow between partners and enable colonized plants to tolerate stressed conditions are encouraged. Both Original Research Articles and Reviews are welcomed and include studies focusing on:
• Role of plant hormones in nodulation and actinorhizal associations
• Role of hormones in arbuscular mycorrhizal associations
• Role of hormones in ectomycorrhizal associations
• Role of hormones in other plant endophyte associations