Resumen de Bacterial siderophores enhance Fe uptake and trigger tomato growth
W. Radzki, Francisco Javier Gutiérrez Mañero, J. García Cristobal, A. Bonilla, Ana García-Villaraco Velasco, Beatriz Ramos Solano
Iron is crucial element for proper plant development. Its deficiency may lead to disruption ofmany processes including respiration or photosynthesis and be the reason of a chlorosis in theaftermath [1]. Although in most types of soil iron occurs in abundance, only Fe2+ forms areavailable for plants because Fe3+ ions often form insoluble oxides or hydroxides. Therefore,providing plants with accessible form of iron is necessary when it is scant or unavailable in soils[1]. Some microbes developed strategies which enable them to acquire iron from the soil byreleasing siderophores - the compounds capable of chelating Fe with high affinity [2]. The aimof this investigation was to determine the effect of siderophores produced by a PGPR strain andby the PGPR itself on iron-starved tomato plants showing chlorotic symptoms.The ability of two bacterial strains releasing siderophores was evaluated in MM9 medium [3].The best of these two was used for biological assay. Plants were grown under iron starvationconditions in hydroponics for 12 weeks. Then the following treatments were delivered: bacterialliquid culture which contained siderophore-bound iron and culture filtrate free of bacteria alsocontaining siderophore-bound iron in equivalent amounts to full Hoagland solution. Water, andiron free Hoagland solution were used as negative controls and full Hoagland solution as thepositive control. Treatments were delivered twice, with a week in between. Plants wereharvested and biometrical analysis was carried out, chlorophyll content and nutritional status inleaves were measured.Results showed that both bacterial siderophore treatments significantly increased plant yield,chlorophyll and iron content, indicating that the bacterial siderophores are readily absorbed bythe plant, either with or without the bacterial presence, achieving even better results than fullHoagland solution. In addition, microelements namely Al, B and Cu, and the macronutrientsNa, P, S and N were also significantly increased. Interestingly, delivering bacteria to the plantsresulted in a significant increase in shoot dry weight, comparing to the culture filtrate alone,indicating that the bacteria is conferring an additional benefit to the plant other than improvingnutrient absorption. This bacteria or its siderophores appear as a challenging alternative todevelop natural iron chelators.
