title: Mycorrhizal phosphate uptake pathway in maize: vital for growth and cob development on nutrient poor agricultural and greenhouse soils.
abstract: Arbuscular mycorrhizal fungi (AMF) form a mutually beneficial symbiosis with plant roots providing predominantly phosphorus in the form of orthophosphate (Pi) in exchange for plant carbohydrates on low P soils. The goal of this work was to generate molecular-genetic evidence in support of a major impact of the mycorrhizal Pi uptake (MPU) pathway on the productivity of the major crop plant maize under field and controlled conditions. Here we show, that a loss-of-function mutation in the mycorrhiza-specific Pi transporter gene Pht1;6 correlates with a dramatic reduction of above-ground biomass and cob production in agro-ecosystems with low P soils. In parallel mutant pht1;6 plants exhibited an altered fingerprint of chemical elements in shoots dependent on soil P availability. In controlled environments mycorrhiza development was impaired in mutant plants when grown alone. The presence of neighboring mycorrhizal nurse plants enhanced the reduced mycorrhiza formation in pht1;6 roots. Uptake of (33)P-labeled orthophosphate via the MPU pathway was strongly impaired in colonized mutant plants. Moreover, repression of the MPU pathway resulted in a redirection of Pi to neighboring plants. In line with previous results, our data highlight the relevance of the MPU pathway in Pi allocation within plant communities and in particular the role of Pht1;6 for the establishment of symbiotic Pi uptake and for maize productivity and nutritional value in low-input agricultural systems. In a first attempt to identify cellular pathways which are affected by Pht1;6 activity, gene expression profiling via RNA-Seq was performed and revealed a set of maize genes involved in cellular signaling which exhibited differential regulation in mycorrhizal pht1;6 and control plants. The RNA data provided support for the hypothesis that fungal supply of Pi and/or Pi transport across Pht1;6 affects cell wall biosynthesis and hormone metabolism in colonized root cells.
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany ; Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne Cologne, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Willmann
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Gerlach
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Buer
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Polatajko
authors.affiliation: Experimental Station Eschikon, Institute of Agricultural Sciences, Federal Institute of Technology Zurich (ETH) Lindau, Switzerland.
authors.forename: Réka
authors.initials: R
authors.lastname: Nagy
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Koebke
authors.affiliation: Experimental Station Eschikon, Institute of Agricultural Sciences, Federal Institute of Technology Zurich (ETH) Lindau, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Jansa
authors.affiliation: Agroscope Reckenholz-Tänikon Research Station ART Zurich, Switzerland.
authors.forename: René
authors.initials: R
authors.lastname: Flisch
authors.affiliation: Botanical Institute, University of Cologne Cologne, Germany ; Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne Cologne, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Bucher
keywords: Zea mays; arbuscular mycorrhiza; phosphate transporter; phosphorus nutrition; plant biomass