Systemic resistance and lipoxygenase-related defence response induced in tomato by Pseudomonas putida strain BTP1

BACKGROUND: Previous studies showed the ability of Pseudomonas putida strain BTP1 to promote induced systemic resistance (ISR) in different host plants. Since ISR is long-lasting and not conducive for development of resistance of the targeted pathogen, this phenomenon can take part of disease control strategies. However, in spite of the numerous examples of ISR induced by PGPR in plants, only a few biochemical studies have associated the protective effect with specific host metabolic changes. RESULTS: In this study, we showed the protective effect of this bacterium in tomato against Botrytis cinerea. Following treatment by P. putida BTP1, analyses of acid-hydrolyzed leaf extracts showed an accumulation of antifungal material after pathogen infection. The fungitoxic compounds thus mainly accumulate as conjugates from which active aglycones may be liberated through the activity of hydrolytic enzymes. These results suggest that strain BTP1 can elicit systemic phytoalexin accumulation in tomato as one defence mechanism. On another hand, we have shown that key enzymes of the lipoxygenase pathway are stimulated in plants treated with the bacteria as compared with control plants. Interestingly, this stimulation is observed only after pathogen challenge in agreement with the priming concept almost invariably associated with the ISR phenomenon. CONCLUSION: Through the demonstration of phytoalexin accumulation and LOX pathway stimulation in tomato, this work provides new insights into the diversity of defence mechanisms that are inducible by non-pathogenic bacteria in the context of ISR

In Vitro Preservation of Yam (Dioscorea cayenensis D. rotundata complex) for a Better Use of Genetic Resources

Among the food crops, yam takes up quantitatively the first place in the gabonese diet. Unfortunately, it can stay available only 6 to 7 months in the year because of difficulties of harvest and post- harvest. This problem is little studied in the case of Dioscorea cayenensis-D. rotundata complex. In order to optimize the use of micro tubers for the growing in green house or field, it is important to control the duration of storage before the germination. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormone, the tubers rapidly sprouted in in vitro conditions. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. The size of the tubers used for the storage had great influence on further sprouting. The upper microtubers in 25 mm can be kept to the darkness, under 50% of relative humidity, in 25C during at least 18 weeks. Sprouting is 100% whatever the substrate of culture. The plant tissue culture technique constitutes a serious alternative for the preservation of plant kinds and for the production of planting material. These techniques allow multiplying in a short time of thousands of copies of new varieties of newly created plants. These in vitro plants can be used on one hand, for the production planting material, and on the other hand for ex vitro storage of breeding grounds with decelerated growth, to struggle against genetic erosion. These results should allow improving in practice the multiplication of yam, while guaranteeing </span

Antioxidant fractions and phenolic constituents from leaves of Pluchea carolinensis and Pluchea rosea

peer reviewedAbstract: Objective: To evaluated the antioxidant potential of several polar fractions of P. carolinensis and P. rosea as well as pure chemicals, some of them quantified in both species by HPLC. Methods: The antioxidant potential of polar fractions and pure chemicals were assayed by 2,2-diphenyl-1-picrylhydrazyl and oxygen radical potential methods. The phenolic content was performed by using Folin–Ciocalteu’s reagent. Specific phenolic acids and flavonoids were quantified by DAD-RP-HPLC. Results: The highest DPPH antioxidant potential expressed in mg TE/gDE were frequently measured in fractions from n-butyl alcohol i.e 2 (192.1 ± 0.3); 6 (181.0 ± 0.1) of P. carolinensis and in fraction 7 (188.1 ± 5.5) of P. rosea while for ORAC (mg TE/gDE) assay fraction 2 (543.0 ± 64.6) and 4 (501.4 ± 49.7) of P. carolinensis and 3 (401.3 ± 16.1) and 6 (401.3 ± 16.1) of P. rosea showed the best results. Some flavonoids and phenolic acids were also assayed; all of them showed highest Oxygen radical absorbance capacity values. Conclusion: We report the antioxidant potential of polar fractions, as well as of some pure phenolics responsible of the antioxidant potential. Some phenolics were identified and quantified for the first time in both species. Apparently, caffeoylquinic acid derivatives contribute more significant to the total antioxidant potential of the extracts

Special symposium: In vitro plant recalcitrance loss of plant organogenic totipotency in the course of In vitro neoplastic progression

Summary: The aptitude for organogenesis from normal hormone-dependent cultures very commonly decreases as the tissues are serially subcultured. The reasons for the loss of regenerative ability may vary under different circumstances: genetic variation in the cell population, epigenetic changes, disappearance of an organogenesis-promoting substance, etc. The same reasons may be evoked for the progressive and eventually irreversible loss of organogenic totipotency in the course of neoplastic progressions from hormone-independent tumors and hyperhydric teratomas to cancers. As in animal cells, plant cells at the end of a neoplastic progression have probably undergone several independent genetic accidents with cumulative effects. They indeed are characterized by atypical biochemical cycles from which they are apparently unable to escape. The metabolic changes are probably not the primary defects that cause cancer, rather they may allow the cells to survive. How these changes, namely an oxidative stress, affect organogenesis is not known. The literature focuses on somatic mutations and epigenetic changes that cause aberrant regulation of cell cycle genes and their machiner

Reprogramming of fatty acid and oxylipin synthesis in rhizobacteria-induced systemic resistance in tomato

The rhizobacterium Pseudomonas putida BTP1 stimulates induced systemic resistance (ISR) in tomato. A previous work showed that the resistance is associated in leaves with the induction of the first enzyme of the oxylipin pathway, the lipoxygenase (LOX), leading to a faster accumulation of its product, the free 13-hydroperoxy octadecatrienoic acid (13-HPOT), 2 days after Botrytis cinerea inoculation. In the present study, we further investigated the stimulation of the oxylipin pathway: metabolites and enzymes of the pathway were analyzed to understand the fate of the 13-HPOT in ISR. Actually the stimulation began upstream the LOX: free linolenic acid accumulated faster in P. putida BTP1-treated plants than in control. Downstream, the LOX products 13-fatty acid hydroperoxides esterified to galactolipids and phospholipids were more abundant in bacterized plants than in control before infection. These metabolites could constitute a pool that will be used after pathogen attack to produce free fungitoxic metabolites through the action of phospholipase A2, which is enhanced in bacterized plants upon infection. Enzymatic branches which can use as substrate the fatty acid hydroperoxides were differentially regulated in bacterized plants in comparison to control plants, so as to lead to the accumulation of the most fungitoxic compounds against B. cinerea. Our study, which is the first to demonstrate the accumulation of an esterified defense metabolite during rhizobacteria-mediated induced systemic resistance, showed that the oxylipin pathway is differentially regulated. It suggests that this allows the plant to prepare to a future infection, and to respond faster and in a more effective way to B. cinerea invasion.Peer reviewe

Ex Vivo Antioxidant Capacities of Fruit and Vegetable Juices. Potential In Vivo Extrapolation

Background: In support of claims that their products have antioxidant properties, the food industry and dietary supplement manufacturers rely solely on the in vitro determination of the ORAC (oxygen radical antioxidant capacity) value, despite its acknowledged lack of any in vivo relevance. It thus appears necessary to use tests exploiting biological materials (blood, white blood cells) capable of producing physiological free radicals, in order to evaluate more adequately the antioxidant capacities of foods such as fruit and vegetable juices. Materials: Two approaches to as sessing the antioxidant capacities of 21 commercial fruit and vegetable juices were compared: the ORAC assay and the “PMA–whole blood assay,” which uses whole blood stimulated by phorbol myristate acetate to produce the superoxide anion. We described in another paper the total poly phenol contents (TPCs) and individual phenolic compound contents of all the juices investigated here (Matute et al. Antioxidants 2020, 9, 1–18). Results: Ranking of the juices from highest to lowest antioxidant capacity differed considerably according to the test used, so there was no correlation (r = 0.33, p = 0.13) between the two assays when considering all juices. Although the results of the ORAC assay correlated positively with TPC (r = 0.50, p = 0.02), a much stronger correlation (r = 0.70, p = 0.004) emerged between TPC and % superoxide anion inhibition. In the PMA–whole blood as say, peonidin-3-O-glucoside, epigallocatechin gallate, catechin, and quercetin present in juices were found to inhibit superoxide anion production at concentrations below 1 µM, with a strong positive correlation. Conclusions: Associated with the determination of total and individual phenolic com pounds contained in fruit and vegetable juices, the PMA–whole blood assay appears better than the ORAC assay for evaluating juice antioxidant capacit

Incorporation dans les polysomes en voie de formation des RNAs nouvellement synthétisés pendant la germination du maïs

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Incorporation dans les polysomes en voie de formation des RNAs nouvellement synthétisés pendant la germination du maïs

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe