The Medicago truncatula hypermycorrhizal B9 mutant displays an altered response to phosphate and is more susceptible to Aphanomyces euteiches

Abstract

Inorganic phosphate (Pi) plays a key role in the development of arbuscular mycorrhizal (AM) symbiosis, which is favoured when Pi is limiting in the environment. We have characterized the Medicago truncatula hypermycorrhizal B9 mutant for its response to limiting (P/10) and replete (P2) Pi. On P2, mycorrhization was significantly higher in B9 plants than in wild-type (WT). The B9 mutant displayed hallmarks of Pi-limited plants, including higher levels of anthocyanins and lower concentrations of Pi in shoots than WT plants. Transcriptome analyses of roots of WT and B9 plants cultivated on P2 or on P/10 confirmed the Pi-limited profile of the mutant on P2 and highlighted its altered response to Pi on P/10. Furthermore, the B9 mutant displayed a higher expression of defence/stress-related genes and was more susceptible to infection by the root oomycete pathogen Aphanomyces euteiches than WT plants. We propose that the hypermycorrhizal phenotype of the B9 mutant is linked to its Pi-limited status favouring AM symbiosis in contrast to WT plants in Pi-replete conditions, and discuss the possible links between the altered response of the B9 mutant to Pi, mycorrhization and infection by A. euteiches.

Short chain chito-oligosaccharides promote arbuscular mycorrhizal colonization in Medicago truncatula

“…truncatula (Truong et al, 2014) and Pisum sativum (Jones et al, 2015), where arbuscule proliferation appears analogous to what we have observed upon CO treatment. A few hypotheses can be made to explain this, each of which deserves further investigation.…”

Nitrogen modulation of Medicago truncatula resistance to Aphanomyces euteiches depends on plant genotype

“…As 40 cycles were performed for qPCR analysis, a gene was considered not to be expressed if DCt test gene -reference gene 26. Therefore, gene expression was quantified by the parameter 26 -DCt test gene -reference gene , which is higher when the test gene is more highly expressed (Bari et al, 2006;Truong et al, 2015). When normalizing AeCRN5 and AeCRN13 expression to AeTUB expression, as the average Ct of AeTUB was 28, the value 12 -DCt test gene -AeTUBgene was used for the quantification of gene expression.…”

Unified Transcriptomic Signature of Arbuscular Mycorrhiza Colonization in Roots of Medicago truncatula by Integration of Machine Learning, Promoter Analysis, and Direct Merging Meta-Analysis

“…To reduce the variation between experiments, the Medicago Genome Array of Affymetrix platform with 61278 probset IDs was selected. Some samples in four studies had these criteria (Table 1 , Figure 1 ) (Hogekamp et al, 2011 ; Bonneau et al, 2013 ; Truong et al, 2015 ; Floss et al, 2017 ). These samples were roots colonized with Gigaspora gigantean, Rhizophagus irregularis , or Glomus mosseae as well as non-inoculated ones.…”

“…In the original experiment (Truong et al, 2015 ), the impact of P limitation and both P and N limitation on Medicago truncatula A17 root transcriptome in response to Rhizophagus irregularis (previously known as Glomus intraradices ) were investigated. In the original experiment, the root transcriptome of both wild type plants and a hypermycorrhizal mutant (B9) grown on limiting or non-limiting phosphate were analyzed to determine which processes were in the hypermycorrhizal mutant.…”