The CRE1 cytokinin pathway is differentially recruited depending on Medicago truncatula root environments and negatively regulates resistance to a pathogen

• Published in: PloS one 2015-01, Vol.10 (1), p.e0116819-e0116819
• Main Authors: Laffont, Carole, Rey, Thomas, André, Olivier, Novero, Mara, Kazmierczak, Théophile, Debellé, Frédéric, Bonfante, Paola, Jacquet, Christophe, Frugier, Florian
• Format: Article
• Language: English
• Subjects: Abiotic stress; Alfalfa; Analysis; Aphanomyces; Aphanomyces - pathogenicity; Arabidopsis; Arbuscular mycorrhizas; Cytokinins; Cytokinins - genetics; Cytokinins - metabolism; Environmental stress; Fungi; Gene expression; Genetic aspects; Glomeromycota - pathogenicity; Kinases; Legumes; Life Sciences; Medicago truncatula; Medicago truncatula - growth & development; Medicago truncatula - metabolism; Microbial drug resistance; Mutants; Mutation; Nitrogen - metabolism; Nitrogen fixation; Organogenesis; Phenotype; Phenotyping; Physiological aspects; Plant diseases; Plant hormones; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Roots - drug effects; Plant Roots - growth & development; Plant Roots - metabolism; Plants (botany); Proteins; Root development; Roots; Salts; Seeds; Senescence; Signal Transduction - drug effects; Signaling; Sodium Chloride - pharmacology; Stress response; Survival; Symbiosis; Transcription factors; Transcriptome - drug effects; Vegetal Biology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0116819

Cytokinins are phytohormones that regulate many developmental and environmental responses. The Medicago truncatula cytokinin receptor MtCRE1 (Cytokinin Response 1) is required for the nitrogen-fixing symbiosis with rhizobia. As several cytokinin signaling genes are modulated in roots depending on different biotic and abiotic conditions, we assessed potential involvement of this pathway in various root environmental responses. Phenotyping of cre1 mutant roots infected by the Gigaspora margarita arbuscular mycorrhizal (AM) symbiotic fungus, the Aphanomyces euteiches root oomycete, or subjected to an abiotic stress (salt), were carried out. Detailed histological analysis and quantification of cre1 mycorrhized roots did not reveal any detrimental phenotype, suggesting that MtCRE1 does not belong to the ancestral common symbiotic pathway shared by rhizobial and AM symbioses. cre1 mutants formed an increased number of emerged lateral roots compared to wild-type plants, a phenotype which was also observed under non-stressed conditions. In response to A. euteiches, cre1 mutants showed reduced disease symptoms and an increased plant survival rate, correlated to an enhanced formation of lateral roots, a feature previously linked to Aphanomyces resistance. Overall, we showed that the cytokinin CRE1 pathway is not only required for symbiotic nodule organogenesis but also affects both root development and resistance to abiotic and biotic environmental stresses.