Advances in the response and modulation of phytohormones on arbuscular mycorrhizal symbiosis

ObjectivesArbuscular mycorrhizal (AM) symbiosis that is formed by AM fungi in soil and most land plants is the most widespread mutualistic association in nature. The establishment of AM symbiosis involves complicated pathways of signal exchange and transduction, which are regulated by many genes with stringent and coordinated expression procedures. Plant hormones are well known to be signaling molecules that act in almost all physiological processes during plant growth and development, and also have been demonstrated to play crucial roles in modulating interactions between plants and microbe, including the AM fungi. In this article, the research progresses on the phytohormone-mediated regulation of AM symbiosis in last decade were reviewed.

Major advancesExternal application of low concentration of both auxin and abscisic acid improved the formation of AM symbiosis, while endogenous lack of gibberellin, abscisic acid and brassinolide repressed mycorrhization. Mutants with defection in jasmonic acid biosynthesis retarded AM fungal colonization, and knock down of the receptors of strigoloctone, auxin and abscisic acid inhibited AM symbiosis. Notably, the repressed expression of receptor of auxin not only decreased the AM colonization, but also inhibited the arbuscule abundance in cortical cells.

ExpectationsThe current research regarding the molecular mechanisms underlying the phytohormone-mediated regulation in the establishment of AM symbiosis is still in the early stage. With the rapid development of transgenic and gene editing techniques, such as Crispr/cas9-mediated gene knockout technology, and through the deeply mining of the genomic, transcriptomic, proteomic and metabolomics data set, the scientific questions with respect to AM symbiosis and other plant-microbial interaction systems will be finally answered.