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Bacterial endophytes contribute to abiotic stress adaptation in pepper plants (Capsicum annuum L.)

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Endophytes are nonpathogenic plant-associated bacteria that can play an important role in plant vitality and may confer resistance to abiotic or biotic stress. The effects of 5 endophytic bacterial strains isolated from pepper plants showing 1-aminocyclopropane-1-carboxylate deaminase activity were studied in sweet pepper under in vitro conditions. Four of the strains tested showed production of indole acetic acid. Plant growth, osmotic potential, free proline content, and gene expression were monitored in leaves and roots under control and mild osmotic stress conditions. All indole acetate producers promoted growth in Capsicum annuum L. ‘Ziegenhorn Bello’, from which they were isolated. Osmotic stress caused an increase in the content of free proline in the leaves of both inoculated and noninoculated plants. Inoculated control plants also revealed higher proline levels in comparison with noninoculated control plants. Differential gene expression patterns of CaACCO, CaLTPI, CaSAR82A, and putative P5CR and P5CS genes during moderate stress were observed, depending on the bacterium applied. Inoculation with 2 bacterial strains, EZB4 and EZB8 (Arthrobacter sp. and Bacillus sp., respectively), resulted in a significantly reduced upregulation or even downregulation of the stress-inducible genes CaACCO and CaLTPI, as compared with the gene expression in noninoculated plants. This indicates that both strains reduced abiotic stress in pepper under the conditions tested.

Les endophytes sont des bactéries non pathogènes associées aux plantes qui peuvent jouer un rôle important dans la viabilité de la plante et peuvent conférer une résistance à des stress abiotiques ou biotiques. Les effets de cinq souches bactériennes endophytes isolées de plants de poivrons qui démontrent une activité 1-aminocyclopropane-1-carboxylate désaminase ont été étudiés chez le poivron doux in vitro. Quatre des souches testées produisaient de l’acide indole-acétique. La croissance des plants, le potentiel osmotique, le contenu en proline libre et l’expression génique ont été examinés dans les feuilles et les racines placées en conditions de stress osmotique faible ou contrôle. Toutes les souches qui produisaient de l’acide indole-acétique étaient promotrices de la croissance de Capsicum annuum L. ‘Ziegenhorn Bello’ de la quelle elles avaient été isolées. Le stress osmotique a causé une augmentation du contenu en proline libre dans les feuilles de plants inoculés ou non. Les plants inoculés contrôles ont aussi révélé un contenu élevé en proline libre comparativement aux plants contrôles non inoculés. Lors d’un stress modéré, des patrons différentiels d’expression des gènes CaACCO, CaLTPI, CaSAR82A ainsi que des gènes présumés P5CR et P5CS ont été observés selon la bactérie inoculée. L’inoculation de deux souches bactériennes, EZB4 et EZB8 (Arthrobacter sp. et Bacillus sp.) a résulté en une réduction significative de l’activation, voire une inhibition, de l’expression des gènes CaACCO et CaLTPI inductibles par le stress, comparativement aux plants non inoculés. Ceci indique que les deux souches réduisent le stress abiotique chez le poivron dans les conditions testées.

Document Type: Research Article

Publication date: November 1, 2007

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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