Regulatory Players in Mycorrhizal-Bacterial-Plant Interactions

Mycorrhizae contribute significantly for plant growth and development, often providing nutrients such as phosphate and nitrogen, while also enhancing stress tolerance and resistance against phytopathogens. Plant symbiotic mycorrhizal networks harbor bacterial communities that aid mycorrhizal functions and augment plant nutrition and development. Various bacterial associations of mycorrhiza bring forth advantageous traits to mycorrhizal symbiosis and host colonization, which involves a wide range of signaling and regulatory molecules. These regulatory molecules play an important role in adapting and responding to new microenvironments with different hosts through the production of metabolites and expression of favorable genes. Small molecular components such as noncoding RNA (miRNA and sRNA) are also involved in the regulation and adaptation to these microenvironments. Regulatory pathways involving protein kinases play an important role in the tripartite association of bacteria and mycorrhizal fungi with plants, and the subsequent promotion of symbiotic interactions. This mini-review highlights potential bacterial regulatory candidates which can influence mycorrhiza-plant interactions to significantly benefit plant growth and development. An understanding of these bacterial regulatory mechanisms may suggest new strategies for knowledge-based application in crop productivity improvement programs.