Salicylic Acid, Jasmonic Acid and Ethylene Involved in The Resistance Induced By The Rhizobacterium Pta-Ct2 In Arabidopsis thaliana Against Botrytis cinerea مشارکة حمض الساليسيليک وحمض الياسمونيک والإيثيلين في المقاومة التي تسببها البکتيريا الجذرية PTA-CT2 في نبات (Arabidopsis thaliana) ضد العفن الرمادى (Botrytis cinerea)
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Abstract:
Salicylic acid (SA), Jasmonic acid (JA) and ethylene (ET) have the significant roles in the plants physiologically and in defense against pathogens. To elucidate the role of these three phytohormones in the development of Induced systemic resistance (ISR), it is a systemic immune response that occurs when the roots are colonized by beneficial microbes. The study model of SRI is the combination of specific beneficial strains of Pseudomonas fluorescens PTA-CT2 with Arabidopsis thaliana, the course of camalexin levels was monitored before and after infection with the fungus Botrytis cinerea. To conduct this, we use different mutants and transgenic plants that fail in the pathway of JA (jar1), ethylene (ein2) or NahG (transgenic line degrading salicylic acid [SA]). We are therefore monitoring the evolution of camalexin, a highly lipophilic phytoalexin, before and after bacterization and/or infection. As a consequence of the study, the bacterization induces potentiation of the defenses, which depends on the three signaling pathways. In addition, the recognition of the beneficial bacteria is reduced by JA and ET.Keywords:
Jasmonic acid
Phytoalexin
Systemic Acquired Resistance
Pseudomonas fluorescens
Phytoalexins are antimicrobial secondary metabolites which accumulate in plants against fungal invasion. Their production is triggered not only by fungal invasion, but also by a variety of elicitors. In rice plants, we have shown that CuCl2 is a potent abiotic elicitor. Jasmonic acid has recently become known to play an important role in secondary metabolite production in plants at the cellular level. This led us to speculate, in CuCl2-elicited rice leaves, that JA might also play an important role as a signal transducer for phytoalexin production. The endogenous level of JA increased rapidly in CuCl2-elicited rice leaves, and exogenously applied JA caused a large amount of phytoalexin production in rice leaves. This phytoalexin production by CuCl2 decreased when rice leaves were treated with JA biosynthesis inhibitors, but that by JA did not. JA is thus suggested to play an important role in the elicitation process leading to phytoalexin production in rice leaves.
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Jasmonic acid
Secondary metabolite
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Phytoalexin
Botrytis
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Phytoalexin
Pseudomonas syringae
Botrytis
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In the interaction between grapevines and Botrytis cinerea, one of the main aspects of pathogenicity is fungal ability to degrade phytoalexins synthesized by the plant in response to infection. Laccase-like stilbene oxidase activity in liquid cultures of B. cinerea has been shown to be related to the decrease of phytoalexin concentrations. Recent research and results presented in this paper determined the chemical structure of a pterostilbene metabolite produced by B. cinerea. Study of degradation of pterostilbene that has just one free hydroxy phenyl group function allowed us to determine the oxidative dimerization process undergone by grapevine phytoalexins after B. cinerea infection. The phytopathological significance of this degradation process in the B. cinerea interaction has also been discussed.
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Phytoalexin
Botrytis
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1α,11-Dihydroxy-4α,5α,7β,10β (H)-eremophilane 6 has been examined as a phytoalexin analogue and shown to be a powerful inhibitor of the growth of the plant pathogen, Botrytis cinerea. Its metabolites have been identified.
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Botrytis
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Botrytis cinerea in contact with mature grape berries encounters an environment particularly rich in polyphenols and PR proteins, where the stilbenic phytoalexin trans-resveratrol may accumulate. To mimic conditions similar to those found in grape berries, B. cinerea was grown in vitro with grape PR proteins and polyphenols extracted from mature grapes and with trans-resveratrol. Results showed that in the presence of highly toxic amounts of trans-resveratrol, grape polyphenols allowed total recovery of fungal growth, and proteins allowed partial recovery. These resveratrol-polyphenol or resveratrol-protein combinations also induced a strong release into the medium of laccase activity, which is likely to be involved in trans-resveratrol detoxification. The grape protein pattern changed during fungal growth; most grape proteins quickly disappeared from the culture when polyphenols and trans-resveratrol were present together. Similar protein patterns were obtained in vitro by incubating grape proteins with grape polyphenols and/or trans-resveratrol with a purified B. cinerea laccase. Under these conditions, most proteins became insoluble. The grape protein pattern obtained from grape berries infected by B. cinerea strongly resembled that obtained in vitro by incubating grape proteins and polyphenols with fungal laccase. It seems that B. cinerea, through laccase secretion and activity and by exploiting the berry polyphenols, easily neutralizes the toxicity of grape stilbenic phytoalexins and makes the grape pathogenesis-related proteins insoluble. The effect of laccase, resveratrol and polyphenols on fungal spore germination was also studied. Results showed that resveratrol alone initially does not inhibit the spore germination. But the inhibition was completely relieved by the presence of grape polyphenols. Instead, the pre-incubation of resveratrol with laccase completely inhibited the spore germination. In addition, we investigate the involvement of B. cinerea proteases in the degradation of grape PR proteins. An aspartyl and a tripeptidyl protease were purified from B. cinerea in vitro culture. The purified proteases activities partially degraded PR proteins. The expression analysis of tripeptidyl and aspartic protease gene families revealed that several members of these families are expressed in the presence of grape PR proteins.
In conclusion, our results support that in a grape berry environment characterized by an abundance of polyphenols, B. cinerea laccase not only detoxify the trans-resveratrol but also modifies the solubility of grape proteins and this environment may facilitate the fungal protease to degrade grape PR proteins.
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Grape seed extract
Spore germination
Botrytis
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Abstract Although germin‐like proteins (GLPs) have been demonstrated to participate in plant biotic stress responses, their specific functions in rice disease resistance are still largely unknown. Here, we report the identification and characterization of OsGLP3‐7 , a member of the GLP family in rice. Expression of OsGLP3‐7 was significantly induced by pathogen infection, jasmonic acid (JA) treatment, and hydrogen peroxide (H 2 O 2 ) treatment. OsGLP3‐7 was highly expressed in leaves and sublocalized in the cytoplasm. Overexpression of OsGLP3‐7 increased plant resistance to leaf blast, panicle blast, and bacterial blight, whereas disease resistance in OsGLP3‐7 RNAi silenced plants was remarkably compromised, suggesting this gene is a positive regulator of disease resistance in rice. Further analysis showed that OsGLP3‐7 has superoxide dismutase (SOD) activity and can influence the accumulation of H 2 O 2 in transgenic plants. Many genes involved in JA and phytoalexin biosynthesis were strongly induced, accompanied with elevated levels of JA and phytoalexins in OsGLP3‐7 ‐overexpressing plants, while expression of these genes was significantly suppressed and the levels of JA and phytoalexins were reduced in OsGLP3‐7 RNAi plants compared with control plants, both before and after pathogen inoculation. Moreover, we showed that OsGLP3‐7 ‐dependent phytoalexin accumulation may, at least partially, be attributed to the elevated JA levels observed after pathogen infection. Taken together, our results indicate that OsGLP3‐7 positively regulates rice disease resistance by activating JA and phytoalexin metabolic pathways, thus providing novel insights into the disease resistance mechanisms conferred by GLPs in rice.
Phytoalexin
Jasmonic acid
Genetically modified rice
Pathogenesis-related protein
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Jasmonic acid
Phytoalexin
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Phytoalexin
Botrytis
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Phytoalexin
Grape seed extract
Botrytis
Pathogenesis-related protein
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