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 33P-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.

Arbuscular Mycorrhizal Fungi Regulate the Growth and Phyto-Active Compound of Salvia miltiorrhiza Seedlings

“…Arbuscular mycorrhizae fungi (AMFs) can form symbiotic relationships with the vast majority of land plants, enhance biomass and growth rates, improve stress resistance, stimulate mineral nutrients uptake and raise photosynthesis of the infected plants [1][2][3]. For instance, P uptake and growth parameters of cowpea plants were positively influenced by AMFs inoculation under a medium or low P fertilization treatment [4].…”

Selective induction of putative iron transporters,OPT8a and OPT8b, in maize by mycorrhizal colonization

“…analyses showed that the symbiotic phosphate transporter ZmPT6, which expresses in mycorrhizal roots and is required for phosphate uptake via AM fungi (Willmann et al 2013), was specifically expressed in the inoculated roots (Fig. 2).…”

Network of GRAS Transcription Factors Involved in the Control of Arbuscule Development inLotus japonicus

“…RNAseq was performed as described previously (Willmann et al, 2013). In brief, .1 mg of molecular grade DNA-free RNA from each sample was used for transcriptome analysis.…”

“…In M. truncatula and rice, loss of function mutations in STR genes resulted in stunted arbuscules (Zhang et al, 2010;Gutjahr et al, 2012), suggesting a role of STR proteins in the transport of metabolites that are essential for a functional root-AMF interaction. Mycorrhiza-specific Pi transporters, such as M. truncatula PHOSPHATE TRANSPORTER4 (MtPT4), Rice PHOSPHATE TRANSPORTER11 (OsPT11), and maize (Zea mays) PHOSPHATE TRANSPORTER1;6 (Pht1;6), localize to arbuscule-containing cells and are indispensable for maintenance of arbuscule function (Javot et al, 2007;Yang et al, 2012;Willmann et al, 2013). Loss-of-function mutants and RNAi lines of MtPT4, OsPT11, and maize pht1;6 mutant led to reduced root colonization with premature degeneration of the arbuscules.…”