Combined genetic and transcriptomic analysis reveals three major signalling pathways activated by Myc-LCOs in Medicago truncatula.
Myc-LCOs are newly identified symbiotic signals produced by arbuscular mycorrhizal (AM) fungi. Like rhizobial Nod factors, they are lipo-chitooligosaccharides that activate the common symbiotic signalling pathway (CSSP) in plants. To increase our limited understanding of the roles of Myc-LCOs we aimed to analyse Myc-LCO-induced transcriptional changes and their genetic control. Whole genome RNA sequencing (RNA-seq) was performed on roots of Medicago truncatula wild-type plants, and dmi3 and nsp1 symbiotic mutants affected in nodulation and mycorrhizal signalling. Plants were treated separately with the two major types of Myc-LCOs, sulphated and nonsulphated. Generalized linear model analysis identified 2201 differentially expressed genes and classified them according to genotype and/or treatment effects. Three genetic pathways for Myc-LCO-regulation of transcriptomic reprogramming were highlighted: DMI3- and NSP1-dependent; DMI3-dependent and NSP1-independent; and DMI3- and NSP1-independent. Comprehensive analysis revealed overlaps with previous AM studies, and highlighted certain functions, especially signalling components and transcription factors. These data provide new insights into mycorrhizal signalling mechanisms, supporting a role for NSP1, and specialisation for NSP1-dependent and -independent pathways downstream of DMI3. Our data also indicate significant Myc-LCO-activated signalling upstream of DMI3 and/or parallel to the CSSP and some constitutive activity of the CSSP.
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Céline
C
Camps
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.|INPT-Université de Toulouse, ENSAT, Avenue de l'Agrobiopole, Auzeville-Tolosane, F-31326, Castanet-Tolosan, France.
Marie-Françoise
MF
Jardinaud
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
David
D
Rengel
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Sébastien
S
Carrère
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Christine
C
Hervé
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Frédéric
F
Debellé
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Pascal
P
Gamas
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Sandra
S
Bensmihen
INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, F-31326, Castanet-Tolosan, France.|CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, F-31326, Castanet-Tolosan, France.
Clare
C
Gough
D002686:Chitin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D048271:Chitosan; D062610:Fungal Polysaccharides / Q000378:metabolism / Q000494:pharmacology*; D005658:Fungi / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D005838:Genotype; D046913:Medicago truncatula / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D009154:Mutation; D038821:Mycorrhizae; D009844:Oligosaccharides; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D013559:Symbiosis / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D059467:Transcriptome / Q000187:drug effects
D062610:Fungal Polysaccharides; D009844:Oligosaccharides; D010940:Plant Proteins; D014157:Transcription Factors; C493484:oligochitosan; D002686:Chitin; D048271:Chitosan
Medicago truncatula; Symbiosis; Transcriptomics; arbuscular mycorrhizal (AM) fungi; common symbiotic signalling pathway (CSSP); lipo-chitooligosaccharides (LCOs)