title: Physiological and antioxidant responses of Medicago sativa-rhizobia symbiosis to cyanobacterial toxins (Microcystins) exposure.
abstract: Toxic cyanobacteria in freshwaters can induce potent harmful effects on growth and development of plants irrigated with contaminated water. In this study, the effect of cyanobacteria extract containing Microcystins (MC) on Medicago sativa-rhizobia symbiosis was investigated in order to explore plants response through biomass production, photosynthetic pigment and antioxidant enzymes analysis: Peroxidase (POD), Polyphenoloxidase (PPO) and Catalase (CAT). Alfalfa plants were inoculated with two endosymbiotic rhizobial strains: RhOL1 (MC less sensitive strain) and RhOL3 (MC more sensitive strain), to evaluate the rhizobial contribution on the plant response cultured under cyanobacterial toxins stress. The two rhizobia strains were identified as Ensifer meliloti by sequence analysis of their rrs and atpD genes. The chronic exposure to MC extract showed shoot, root and nodules dry weight decrease, in both symbiosis cultures. The rate of decline in plants inoculated with RhOL3 was higher than that in symbiosis with RhOL1 mainly at 20 μg L(-1) of MC. Cyanotoxins also reduced photosynthetic pigment content and generated an oxidative stress observed at cellular level. POD, PPO and CAT activities were significantly increased in leaves, roots and nodules of alfalfa plants exposed to MC. These enzyme activities were higher in plants inoculated with RhOL3 especially when alfalfa plants were exposed to 20 μg L(-1) of MC. The present paper reports new scientific finding related to the behavior of rhizobia-M. sativa associations to MC (Microcystins) for later recommendation concerning the possible use of these symbiosis face to crops exposure to MC contaminated water irrigation.
authors.affiliation: Laboratory of Biology and Biotechnology of Microorganisms, Environmental Microbiology and Toxicology Unit, Faculty of Sciences Semlalia, Cadi Ayyad University, PO Box 2390, Marrakech, Morocco.
authors.forename: Fatima
authors.initials: F
authors.lastname: El Khalloufi
authors.forename: Khalid
authors.initials: K
authors.lastname: Oufdou
authors.forename: Majida
authors.initials: M
authors.lastname: Lahrouni
authors.forename: Mustapha
authors.initials: M
authors.lastname: Faghire
authors.forename: Alvaro
authors.initials: A
authors.lastname: Peix
authors.forename: Martha Helena
authors.initials: MH
authors.lastname: Ramírez-Bahena
authors.forename: Vitor
authors.initials: V
authors.lastname: Vasconcelos
authors.forename: Brahim
authors.initials: B
authors.lastname: Oudra
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D008387:Marine Toxins; D000455:Medicago sativa / Q000187:drug effects* / Q000254:growth & development / Q000382:microbiology; D052998:Microcystins / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D010788:Photosynthesis / Q000187:drug effects; D010802:Phylogeny; D012231:Rhizobium / Q000187:drug effects* / Q000378:metabolism; D013559:Symbiosis / Q000187:drug effects
chemical_list: D000975:Antioxidants; D008387:Marine Toxins; D052998:Microcystins; C057862:cyanoginosin LR
keywords: Irrigation; Medicago sativa; Microcystins; Oxidative stress; Rhizobia; Symbiosis