title: The role of pre-symbiotic auxin signaling in ectendomycorrhiza formation between the desert truffle Terfezia boudieri and Helianthemum sessiliflorum.
abstract: The ectendomycorrhizal fungus Terfezia boudieri is known to secrete auxin. While some of the effects of fungal auxin on the plant root system have been described, a comprehensive understanding is still lacking. A dual culture system to study pre mycorrhizal signal exchange revealed previously unrecognized root-fungus interaction mediated by the fungal auxin. The secreted fungal auxin induced negative taproot gravitropism, attenuated taproot growth rate, and inhibited initial host development. Auxin also induced expression of Arabidopsis carriers AUX1 and PIN1, both of which are involved in the gravitropic response. Exogenous application of auxin led to a root phenotype, which fully mimicked that induced by ectomycorrhizal fungi. Co-cultivation of Arabidopsis auxin receptor mutants tir1-1, tir1-1 afb2-3, tir1-1 afb1-3 afb2-3, and tir1-1 afb2-3 afb3-4 with Terfezia confirmed that auxin induces the observed root phenotype. The finding that auxin both induces taproot deviation from the gravity axis and coordinates growth rate is new. We propose a model in which the fungal auxin induces horizontal root development, as well as the coordination of growth rates between partners, along with the known auxin effect on lateral root induction that increases the availability of accessible sites for colonization at the soil plane of fungal spore abundance. Thus, the newly observed responses described here of the root to Terfezia contribute to a successful encounter between symbionts.
authors.affiliation: The Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel.
authors.forename: Tidhar
authors.initials: T
authors.lastname: Turgeman
authors.affiliation: Life Sciences Department, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Olga
authors.initials: O
authors.lastname: Lubinsky
authors.affiliation: Life Sciences Department, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Nurit
authors.initials: N
authors.lastname: Roth-Bejerano
authors.affiliation: Life Sciences Department, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Varda
authors.initials: V
authors.lastname: Kagan-Zur
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet-Dagan, 50250, Israel.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Kapulnik
authors.affiliation: Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Bet-Dagan, 50250, Israel.
authors.forename: Hinanit
authors.initials: H
authors.lastname: Koltai
authors.affiliation: Agricultural Research Organization, Gilat Research Center, 85280, Beer-Sheva, Israel.
authors.forename: Eli
authors.initials: E
authors.lastname: Zaady
authors.affiliation: Department of Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, 84105, Beer-Sheva, Israel.
authors.forename: Shimon
authors.initials: S
authors.lastname: Ben-Shabat
authors.affiliation: Desert Agro-Research Center, Ramat-Negev R & D, D.N, 85515, Halutza, Israel.
authors.forename: Ofer
authors.initials: O
authors.lastname: Guy
authors.affiliation: Department of Vegetable Crops, Newe Yaár Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay, Israel.
authors.forename: Efraim
authors.initials: E
authors.lastname: Lewinsohn
authors.affiliation: The Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel. sitrit@bgu.ac.il.
authors.forename: Yaron
authors.initials: Y
authors.lastname: Sitrit
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001203:Ascomycota / Q000378:metabolism*; D030601:Cistaceae / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D038821:Mycorrhizae / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology / Q000502:physiology; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids
keywords: Auxin; Desert truffle; Gravitropism; Helianthemum sessiliflorum; Terfezia boudieri