title: Unraveling the effect of arsenic on the model Medicago-Ensifer interaction: a transcriptomic meta-analysis.
abstract: The genetic regulation underlying the effect of arsenic (As(III)) on the model symbiosis Medicago-Ensifer was investigated using a combination of physiological (split-roots), microscopy and genetic (microarrays, qRT-PCR and composite plants) tools. Nodulation was very sensitive to As(III) (median inhibitory dose (ID50) = 20 μM). The effect on root elongation and on nodulation was local (nonsystemic). A battery of stress (salt, drought, heat shock, metals, etc.)-related genes were induced. Glutathione played a pivotal role in tolerance/detoxification, together with secondary metabolites ((iso)flavonoids and phenylpropanoids). However, antioxidant enzymes were not activated. Concerning the symbiotic interaction, molecular evidence suggesting that rhizobia alleviate As stress is for the first time provided. Chalcone synthase (which is involved in the first step of the legume-rhizobia cross-talk) was strongly enhanced, suggesting that the plants are biased to establish symbiotic interactions under As(III) stress. In contrast, 13 subsequent nodulation genes (involved in nodulation factors (Nod factors) perception, infection, thread initiation and progression, and nodule morphogenesis) were repressed. Overexpression of the ethylene responsive factor ERN in composite plants reduced root stress and partially restored nodulation, whereas overexpression of the early nodulin ENOD12 enhanced nodulation both in the presence and, particularly, in the absence of As, without affecting root elongation. Several transcription factors were identified, which could be additional targets for genetic engineering aiming to improve nodulation and/or alleviate root stress induced by this toxic.
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Farmacia, Universidad de Sevilla, C/ Profesor García González 2, 41012, Sevilla, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lafuente
authors.forename: Patricia
authors.initials: P
authors.lastname: Pérez-Palacios
authors.forename: Bouchra
authors.initials: B
authors.lastname: Doukkali
authors.forename: María D
authors.initials: MD
authors.lastname: Molina-Sánchez
authors.forename: José I
authors.initials: JI
authors.lastname: Jiménez-Zurdo
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Caviedes
authors.forename: Ignacio D
authors.initials: ID
authors.lastname: Rodríguez-Llorente
authors.forename: Eloísa
authors.initials: E
authors.lastname: Pajuelo
mesh_terms: D001151:Arsenic / Q000633:toxicity*; D018053:Arsenites / Q000633:toxicity; D016000:Cluster Analysis; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D046913:Medicago truncatula / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000382:microbiology*; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D055170:Plant Root Nodulation / Q000187:drug effects / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D020579:Sinorhizobium / Q000502:physiology*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013559:Symbiosis / Q000187:drug effects / Q000235:genetics*; D059467:Transcriptome / Q000235:genetics*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D018053:Arsenites; D010940:Plant Proteins; D012333:RNA, Messenger; C015001:arsenite; D001151:Arsenic
keywords: arsenic; legumes; metalloid; microarrays; nodulation; pollution; rhizobia, split-root