title: Partial resistance of Medicago truncatula to Aphanomyces euteiches is associated with protection of the root stele and is controlled by a major QTL rich in proteasome-related genes.
abstract: A pathosystem between Aphanomyces euteiches, the causal agent of pea root rot disease, and the model legume Medicago truncatula was developed to gain insights into mechanisms involved in resistance to this oomycete. The F83005.5 French accession and the A17-Jemalong reference line, susceptible and partially resistant, respectively, to A. euteiches, were selected for further cytological and genetic analyses. Microscopy analyses of thin root sections revealed that a major difference between the two inoculated lines occurred in the root stele, which remained pathogen free in A17. Striking features were observed in A17 roots only, including i) frequent pericycle cell divisions, ii) lignin deposition around the pericycle, and iii) accumulation of soluble phenolic compounds. Genetic analysis of resistance was performed on an F7 population of 139 recombinant inbred lines and identified a major quantitative trait locus (QTL) near the top of chromosome 3. A second study, with near-isogenic line responses to A. euteiches confirmed the role of this QTL in expression of resistance. Fine-mapping allowed the identification of a 135-kb sequenced genomic DNA region rich in proteasome-related genes. Most of these genes were shown to be induced only in inoculated A17. Novel mechanisms possibly involved in the observed partial resistance are proposed.
authors: Université de Toulose, Toulose, France.
authors: Naceur
authors: N
authors: Djébali
authors: Alain
authors: A
authors: Jauneau
authors: Carine
authors: C
authors: Ameline-Torregrosa
authors: Fabien
authors: F
authors: Chardon
authors: Valérie
authors: V
authors: Jaulneau
authors: Catherine
authors: C
authors: Mathé
authors: Arnaud
authors: A
authors: Bottin
authors: Marc
authors: M
authors: Cazaux
authors: Marie-Laure
authors: ML
authors: Pilet-Nayel
authors: Alain
authors: A
authors: Baranger
authors: Mohamed Elarbi
authors: ME
authors: Aouani
authors: Marie-Thérèse
authors: MT
authors: Esquerré-Tugayé
authors: Bernard
authors: B
authors: Dumas
authors: Thierry
authors: T
authors: Huguet
authors: Christophe
authors: C
authors: Jacquet
mesh_terms: D044744:Aphanomyces / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007113:Immunity, Innate / Q000235:genetics; D007178:Inbreeding; D046913:Medicago truncatula / Q000166:cytology / Q000235:genetics / Q000382:microbiology*; D020161:Physical Chromosome Mapping; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000382:microbiology*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics*; D040641:Quantitative Trait Loci / Q000235:genetics*; D015203:Reproducibility of Results
chemical_list: D046988:Proteasome Endopeptidase Complex