RESUMO
Adaptation ex vitro is strongly stressful for microplants. Plant-growth-promoting rhizobacteria (PGPR) help to increase the adaptation potential of microplants transplanted from test tubes into the natural environment. We investigated the mechanisms of antioxidant protection of PGPR-inoculated potato microclones adapting to ex vitro growth in an aeroponic system. Potato (Solanum tuberosum L. cv. Nevsky) microplants were inoculated in vitro with the bacteria Azospirillum baldaniorum Sp245 and Ochrobactrum cytisi IPA7.2. On days 1 and 7 of plant growth ex vitro, catalase and peroxidase activities in the leaves of inoculated plants were 1.5-fold higher than they were in non-inoculated plants. The activity of ascorbate peroxidase was reduced in both in vitro and ex vitro treatments, and this reduction was accompanied by a decrease in the leaf content of hydrogen peroxide and malondialdehyde. As a result, inoculation contributed to the regulation of the plant pro/antioxidant system, lowering the oxidative stress and leading to better plant survival ex vitro. This was evidenced by the higher values of measured morphological and physiological variables of the inoculated plants, as compared with the values in the control treatment. Thus, we have shown some PGPR-mediated mechanisms of potato plant protection from adverse environmental factors under aeroponic conditions.
RESUMO
Coumarins are a structurally varied set of 2H-chromen-2-one compounds categorized also as members of the benzopyrone group of secondary metabolites. Coumarin derivatives attract interest owing to their wide practical application and the unique reactivity of fused benzene and pyrone ring systems in molecular structure. Coumarins have their own specific fingerprints as antiviral, antimicrobial, antioxidant, anti-inflammatory, antiadipogenic, cytotoxic, apoptosis, antitumor, antitubercular, and cytotoxicity agents. Natural products have played an essential role in filling the pharmaceutical pipeline for thousands of years. Biological effects of natural coumarins have laid the basis of low-toxic and highly effective drugs. Presently, more than 1300 coumarins have been identified in plants, bacteria, and fungi. Fungi as cultivated microbes have provided many of the nature-inspired syntheses of chemically diverse drugs. Endophytic fungi bioactivities attract interest, with applications in fields as diverse as cancer and neuronal injury or degeneration, microbial and parasitic infections, and others. Fungal mycelia produce several classes of bioactive molecules, including a wide group of coumarins. Of promise are further studies of conditions and products of the natural and synthetic coumarins' biotransformation by the fungal cultures, aimed at solving the urgent problem of searching for materials for biomedical engineering. The present review evaluates the fungal coumarins, their structure-related peculiarities, and their future therapeutic potential. Special emphasis has been placed on the coumarins successfully bioprospected from fungi, whereas an industry demand for the same coumarins earlier found in plants has faced hurdles. Considerable attention has also been paid to some aspects of the molecular mechanisms underlying the coumarins' biological activity. The compounds are selected and grouped according to their cytotoxic, anticancer, antibacterial, antifungal, and miscellaneous effects.
RESUMO
Paenibacillus polymyxa is a promising plant-growth-promoting rhizobacterium that associates with a wide range of host plants, including agronomically important ones. Inoculation of wheat seedlings with P. polymyxa strains CCM 1465 and 92 was found to increase the mitotic index of the root cells 1.2- and 1.6-fold, respectively. Treatment of seedlings with the exopolysaccharides (EPSs) of these strains increased the mitotic index 1.9-fold (P. polymyxa CCM 1465) and 2.8-fold (P. polymyxa 92). These increases indicate activation of cell division in the root meristems. Analysis of the morphometric variables of the seedlings showed that P. polymyxa CCM 1465, P. polymyxa 92, and their EPSs promoted wheat growth, increasing root and shoot length up to 22% and root and shoot dry weight up to 28%, as compared with the control. In addition, both strains were found to intensely colonize the seedling root surface. Thus, P. polymyxa EPSs are active metabolites that, along with whole cells, are responsible for the contact interactions of the bacteria with wheat roots and are implicated in the induction of plant responses to these interactions. The strains used in this work are of interest for further study to broaden the existing understanding of the mechanisms of plant-bacterial interactions and to develop effective biofertilizers for agricultural purposes.
Assuntos
Inoculantes Agrícolas/metabolismo , Paenibacillus polymyxa/metabolismo , Polissacarídeos Bacterianos/metabolismo , Plântula/crescimento & desenvolvimento , Triticum/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Plântula/microbiologia , Microbiologia do Solo , Triticum/crescimento & desenvolvimentoRESUMO
Water deficits inhibit plant growth and decrease crop productivity. Remedies are needed to counter this increasingly urgent problem in practical farming. One possible approach is to utilize rhizobacteria known to increase plant resistance to abiotic and other stresses. We therefore studied the effects of inoculating the culture medium of potato microplants grown in vitro with Azospirillum brasilense Sp245 or Ochrobactrum cytisi IPA7.2. Growth and hormone content of the plants were evaluated under stress-free conditions and under a water deficit imposed with polyethylene glycol (PEG 6000). Inoculation with either bacterium promoted the growth in terms of leaf mass accumulation. The effects were associated with increased concentrations of auxin and cytokinin hormones in the leaves and stems and with suppression of an increase in the leaf abscisic acid that PEG treatment otherwise promoted in the potato microplants. O. cytisi IPA7.2 had a greater growth-stimulating effect than A. brasilense Sp245 on stressed plants, while A. brasilense Sp245 was more effective in unstressed plants. The effects were likely to be the result of changes to the plant's hormonal balance brought about by the bacteria.
Assuntos
Azospirillum brasilense/fisiologia , Ochrobactrum/fisiologia , Reguladores de Crescimento de Plantas/metabolismo , Solanum tuberosum/metabolismo , Solanum tuberosum/microbiologia , Ácido Abscísico/metabolismo , Produção Agrícola/métodos , Produtos Agrícolas/metabolismo , Produtos Agrícolas/microbiologia , Citocininas/metabolismo , Secas , Ácidos Indolacéticos/metabolismo , Pressão Osmótica , Folhas de Planta/metabolismo , Caules de Planta/metabolismo , Polietilenoglicóis , Solanum tuberosum/crescimento & desenvolvimentoRESUMO
The search for effective plant-growth-promoting strains of rhizospheric bacteria that would ensure the resistance of plant-microbial associations to environmental stressors is essential for the design of environmentally friendly agrobiotechnologies. We investigated the interaction of potato (cv. Nevsky) microplants with the plant-growth-promoting bacteria Azospirillum brasilense Sp245 and Ochrobactrum cytisi IPA7.2 under osmotic stress in vitro. The bacteria improved the physiological and biochemical variables of the microplants, significantly increasing shoot length and root number (1.3-fold, on average). Inoculation also led a more effective recovery of the plants after stress. During repair, inoculation contributed to a decreased leaf content of malonic dialdehyde. With A. brasilense Sp245, the decrease was 1.75-fold; with O. cytisi IPA7.2, it was 1.4-fold. During repair, the shoot length, node number, and root number of the inoculated plants were greater than the control values by an average of 1.3-fold with A. brasilense Sp245 and by an average of 1.6-fold with O. cytisi IPA7.2. O. cytisi IPA7.2, previously isolated from the potato rhizosphere, protected the physiological and biochemical processes in the plants under stress and repair better than did A. brasilense Sp245. Specifically, root weight increased fivefold during repair, as compared to the noninoculated plants, while chlorophyll a content remained at the level found in the nonstressed controls. The results indicate that these bacteria can be used as components of biofertilizers. A. brasilense Sp245 has favorable prospects for use in temperate latitudes, whereas O. cytisi IPA7.2 can be successfully used in saline and drought-stressed environments.
Assuntos
Interações entre Hospedeiro e Microrganismos/fisiologia , Pressão Osmótica , Desenvolvimento Vegetal , Solanum tuberosum/microbiologia , Estresse Fisiológico/fisiologia , Azospirillum brasilense/fisiologia , Clorofila A , Contagem de Colônia Microbiana , Secas , Malonatos , Ochrobactrum/fisiologia , Folhas de Planta , Raízes de Plantas/microbiologia , Brotos de Planta , RizosferaRESUMO
We evaluated the effect of lipopolysaccharides from the plant-growth-promoting associative bacterium Azospirillum brasilense Sp245 and from the enteric bacterium Escherichia coli K12 on the morphogenic potential of in vitro-growing somatic calluses of soft spring wheat (Triticum aestivum L. cv. Saratovskaya 29). A genetic model was used that included two near-isogenic lines of T. aestivum L. cv. Saratovskaya 29 with different embryogenic capacities; one of these lines carries the Rht-B1 dwarfing gene, whereas the other lacks it. When added to the nutrient medium, the lipopolysaccharide of A. brasilense Sp245 promoted the formation of calluses with meristematic centers and stimulated the regeneration ability of the cultured tissues in both lines. By contrast, the lipopolysaccharide of the enteric bacterium E. coli K12 barely affected the morphogenetic activity of callus cells and the yield of morphogenic calluses and regenerated plants. These findings indicate that the lipopolysaccharide of the plant-growth-promoting associative bacterium A. brasilense Sp245 specifically enhances the morphogenetic activity of wheat somatic tissues, which increases the efficacy of culturing of genotypes with a relatively low morphogenic potential. The results of the study may contribute to the improvement of the efficacy of plant cell selection and gene engineering and to a better understanding of the mechanisms responsible for plant recognition of lipopolysaccharides of associative bacteria.