title: Abscisic acid promotion of arbuscular mycorrhizal colonization requires a component of the PROTEIN PHOSPHATASE 2A complex.
abstract: Legumes can establish intracellular interactions with symbiotic microbes to enhance their fitness, including the interaction with arbuscular mycorrhizal (AM) fungi. AM fungi colonize root epidermal cells to gain access to the root cortex, and this requires the recognition by the host plant of fungus-made mycorrhizal factors. Genetic dissection has revealed the symbiosis signaling pathway that allows the recognition of AM fungi, but the downstream processes that are required to promote fungal infection are poorly understood. Abscisic acid (ABA) has been shown to promote arbuscule formation in tomato (Solanum lycopersicum). Here, we show that ABA modulates the establishment of the AM symbiosis in Medicago truncatula by promoting fungal colonization at low concentrations and impairing it at high concentrations. We show that the positive regulation of AM colonization via ABA requires a PROTEIN PHOSPHATASE 2A (PP2A) holoenzyme subunit, PP2AB'1. Mutations in PP2AB'1 cause reduced levels of AM colonization that cannot be rescued with permissive ABA application. The action of PP2AB'1 in response to ABA is unlinked to the generation of calcium oscillations, as the pp2aB'1 mutant displays a normal calcium response. This contrasts with the application of high concentrations of ABA that impairs mycorrhizal factor-induced calcium oscillations, suggesting different modes of action of ABA on the AM symbiosis. Our work reveals that ABA functions at multiple levels to regulate the AM symbiosis and that a PP2A phosphatase is required for the ABA promotion of AM colonization.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (M.C., J.S., G.E.D.O.); andSamuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (J.W., K.S.M.) myriam.charpentier@jic.ac.uk giles.oldroyd@jic.ac.uk.
authors.forename: Myriam
authors.initials: M
authors.lastname: Charpentier
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (M.C., J.S., G.E.D.O.); andSamuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (J.W., K.S.M.).
authors.forename: Jongho
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (M.C., J.S., G.E.D.O.); andSamuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (J.W., K.S.M.).
authors.forename: Jiangqi
authors.initials: J
authors.lastname: Wen
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (M.C., J.S., G.E.D.O.); andSamuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (J.W., K.S.M.).
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom (M.C., J.S., G.E.D.O.); andSamuel Roberts Noble Foundation, Ardmore, Oklahoma 73401 (J.W., K.S.M.) myriam.charpentier@jic.ac.uk giles.oldroyd@jic.ac.uk.
authors.forename: Giles E D
authors.initials: GE
authors.lastname: Oldroyd
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D020013:Calcium Signaling; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D046913:Medicago truncatula / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D008969:Molecular Sequence Data; D009154:Mutation; D038821:Mycorrhizae / Q000502:physiology*; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis
chemical_list: D010937:Plant Growth Regulators; D010940:Plant Proteins; D000040:Abscisic Acid; D054648:Protein Phosphatase 2