Cross-talk interactions of exogenous nitric oxide and sucrose modulates phenylpropanoid metabolism in yellow lupine embryo axes infected with Fusarium oxysporum

AbstractThe aim of the study was to examine cross-talk of exogenous nitric oxide (NO) and sucrose in the mechanisms of synthesis and accumulation of isoflavonoids in embryo axes of Lupinus luteus L. cv. Juno. It was verified whether the interaction of these molecules can modulate the defense response of axes to infection and development of the pathogenic fungus Fusarium oxysporum f. sp. lupini. Sucrose alone strongly stimulated a high level of genistein glucoside in axes pretreated with exogenous nitric oxide (SNP or GSNO) and non-pretreated axes. As a result of amplification of the signal coming from sucrose and GSNO, high isoflavonoids accumulation was observed (+Sn+GSNO). It needs to be stressed that infection in tissues pretreated with SNP/GSNO and cultured on the medium with sucrose (+Si+SNP/+Si+GSNO) very strongly enhances the accumulation of free isoflavone aglycones. In +Si+SNP axes phenylalanine ammonia-lyase activity was high up to 72h. As early as at 12h in +Si+SNP axes an increase was recorded in gene expression level of the specific isoflavonoid synthesis pathway. At 24h in +Si+SNP axes a very high total antioxidant capacity dependent on the pool of fast antioxidants was noted. Post-infection generation of semiquinone radicals was lower in axes with a high level of sucrose than with a deficit

The involvement of carbohydrates in the regulation of the level of endogenous signalling molecules engaged in defence responses of Lupinus luteus L.cv. Juno on Fusarium oxysporum

Uniwersytet Przyrodniczy w Poznaniu: Wydział Ogrodnictwa i Architektury Krajobrazu; Wydział BiologiiCelem pracy było sprawdzenie czy poziom węglowodanów rozpuszczalnych (sacharozy i monosacharydów) w osiach zarodkowych kiełkujących nasion Lupinus luteus L.cv. Juno wpływa na poziom cząsteczek sygnałowych takich jak fitohormony i wolne rodniki oraz jaki może mieć to pośrednio związek z reakcjami obronnymi uruchamianymi względem patogenicznego grzyba Fusarium oxysporum f.sp. lupini. Pozytywną współzależność stwierdzono pomiędzy poziomem węglowodanów a poinfekcyjną akumulacją kwasu salicylowego i jego glukozydu, kwasu abscysynowego i tlenku azotu. Stymulujący wpływ węglowodanów na produkcję estru metylowego kwasu jasmonowego i etylenu odnotowano w późnym czasie po inokulacji. Otrzymane wyniki wskazują także na zaangażowanie węglowodanów w uruchomienie innych mechanizmów obronnych takich jak wzmożenie biosyntezy izoflawonów, generowania anionorodnika ponadtlenkowego i rodników semichinonowych w osiach zarodkowych względem hemibiotroficznego grzyba F. oxysporum. Dodatkowo wykazano amplifikację sygnału indukowanego egzogennym tlenkiem azotu, sacharozą i infekcją powodowaną przez F. oxysporum. Otrzymane wyniki badań dotyczące wyjaśnienia stosunków ilościowych powyższych molekuł sygnałowych i ich znaczenia w stymulacji odpowiedzi obronnych w komórkach osi zarodkowych łubinu żółtego, przyczynią się do lepszego poznania mechanizmów regulacyjnych podczas interakcji roślina-patogen.The aim of the dissertation was to verify whether the level of soluble carbohydrates (sucrose and monosaccharides) in embryo axes of germinating seeds of Lupinus luteus L. cv. Juno affects the level of signalling molecules such as phytohormones and free radicals and how it may be indirectly related with defence reactions triggered against the pathogenic fungus Fusarium oxysporum f. sp. lupini. A positive interdependence was found between the level of carbohydrates and post-infection accumulation of salicylic acid and its glucoside, abscisic acid and nitric oxide. The stimulatory effect of carbohydrates on the production of methyl ester of jasmonic acid and ethylene was recorded at a later time after inoculation. Results also indicate an involvement of carbohydrates in the initiation of other defence mechanisms such as an enhanced biosynthesis of isoflavones, generation of superoxide anion radical and semiquinone radicals in embryo axes in relation to the hemibiotrophic fungus F. oxysporum. Additionally, the experiments showed an amplification of the signal induced by the exogenous nitric oxide, sucrose and infection caused by F. oxysporum. Obtained experimental results concerning the explanation of quantitative ratios of the above mentioned signalling molecules and their importance in the stimulation of defence responses in embryo axes of yellow lupine will contribute to a better understanding of regulatory mechanisms during plant-pathogen interaction

The Role of Sugars in Plant Responses to Stress and Their Regulatory Function during Development

Due to their role as energy and carbon sources and their regulatory functions, sugars influence all phases of the plant life cycle, interact with other signaling molecules, including phytohormones, and control plant growth and development [...

Enhancing Lettuce Drought Tolerance: The Role of Organic Acids in Photosynthesis and Oxidative Defense

The aim of this study was to investigate the effects of maleic acid (MA), salicylic acid (SA), and citric acid (CA) on alleviating the drought stress of a lettuce (Lactuca sativa L.) hydroponic culture. The effect of these organic acids was tested under stress conditions induced by polyethene glycol (PEG 6000) at 5% and 7.5% concentrations. Drought stress reduced the fresh and dry matter yields of plants. The acid treatment caused increasing tendencies in the fresh weight yield:control (SA, MA), PEG 7.5% (SA, MA, CA)) and dry weight yield (control (SA, MA), PEG 5% (MA), PEG 7.5% (SA, MA)). The acid treatment also enhanced the nutrient uptake of stressed plants: SA: N (PEG 7.5%), K (PEG 5 and 7.5%); MA: N, P, K, Ca (PEG 5 and 7.5%). This work found that chlorophyll a and b amounts did not change under applied experimental conditions. Most parameters of chlorophyll fluorescence did not depend on either the level of applied water stress (PEG level) or the type of spraying. Drought stress increased leaf superoxide anion (O2•−) and malondialdehyde (MDA) levels but decreased H2O2. Proline (Pro) and phenolic compounds (TFC), including flavonols (Fla), accumulated more in stressed plants. Drought stress also affected the chlorophyll fluorescence. Our results suggest that acids can improve plant tolerance to drought stress by boosting the antioxidant defence system and reducing the oxidative damage caused by reactive oxygen species

Brachycorynella asparagi (Mordv.) Induced—Oxidative Stress and Antioxidative Defenses of Asparagus officinalis L.

The aim of this study was to investigate whether and to what extent oxidative stress is induced in leaves of one- and two-month-old plants of Asparagus officinalis L. cv. Argenteuil infested by Brachycorynella asparagi (Mordvilko) at a varied population size. The pest B. asparagi has been described as the most damaging species feeding on asparagus. Analyses using electron paramagnetic resonance (EPR) demonstrated generally higher concentrations of semiquinone radicals with g-values of 2.0045 ± 0.0005 and 2.0026 ± 0.0005 in Asparagus officinalis (A. officinalis) leaves after Brachycorynella asparagi (B. asparagi) infestation than in the control. Observations of leaves under a confocal microscope showed a post-infestation enhanced generation of the superoxide anion radical (O2•−) and hydrogen peroxide (H2O2) in comparison to the control. Strong fluctuations in Mn2+ ion levels detected by EPR spectroscopy versus time were detected in leaves infested by aphids, which may indicate the involvement of these ions in the control of O2•− production. An enhanced superoxide dismutase activity is an important element in leaf defense against oxidative stress. Visible symptoms were found in aphid-infested A. officinalis. Damage to leaves of one- and two-month-old A. officinalis plants by the aphid B. asparagi was dependent on the intensity, duration of infestation and plant age

Deoxynivalenol and Oxidative Stress Indicators in Winter Wheat Inoculated with Fusarium graminearum

This study comprises analyses of contents of mycotoxins, such as deoxynivalenol and zearalenone, as well as the level of oxidative stress in ears of a susceptible wheat cultivar Hanseat and cv. Arina, resistant to a pathogenic fungus Fusarium graminearum. Starting from 48 h after inoculation, a marked increase was observed in the contents of these mycotoxins in ears of wheat; however, the greatest accumulation was recorded in the late period after inoculation, i.e., during development of disease. Up to 120 h after inoculation, in ears of both wheat cultivars, the level of deoxynivalenol was higher than that of zearalenone. The susceptible cultivar was characterized by a much greater accumulation of deoxynivalenol than the resistant cultivar. At the same time, in this cultivar, in the time from 0 to 72 h after inoculation, a marked post-infection increase was observed in the generation of the superoxide radical (O2•−). Additionally, its level, at all the time points after inoculation, was higher than in the control. In wheat cv. Arina, a markedly higher level of O2•− generation in relation to the control was found up to two hours after inoculation and, next, at a later time after inoculation. In turn, the level of semiquinone radicals detected by electron paramagnetic resonance (EPR) increased at later culture times, both in cv. Hanseat and Arina; however, in infested ears of wheat, it was generally lower than in the control. Analysis of disease symptoms revealed the presence of more extensive lesions in ears of a susceptible wheat cv. Hanseat than resistant cv. Arina. Additionally, ergosterol level as a fungal growth indicator was higher in ears of susceptible wheat than in the resistant cultivar

Effects of Endogenous Signals and Fusarium oxysporum on the Mechanism Regulating Genistein Synthesis and Accumulation in Yellow Lupine and Their Impact on Plant Cell Cytoskeleton

The aim of the study was to examine cross-talk interactions of soluble sugars (sucrose, glucose and fructose) and infection caused by Fusarium oxysporum f.sp. lupini on the synthesis of genistein in embryo axes of Lupinus luteus L.cv. Juno. Genistein is a free aglycone, highly reactive and with the potential to inhibit fungal infection and development of plant diseases. As signal molecules, sugars strongly stimulated accumulation of isoflavones, including genistein, and the expression of the isoflavonoid biosynthetic genes. Infection significantly enhanced the synthesis of genistein and other isoflavone aglycones in cells of embryo axes of yellow lupine with high endogenous sugar levels. The activity of β-glucosidase, the enzyme that releases free aglycones from their glucoside bindings, was higher in the infected tissues than in the control ones. At the same time, a very strong generation of the superoxide anion radical was observed in tissues with high sugar contents already in the initial stage of infection. During later stages after inoculation, a strong generation of semiquinone radicals was observed, which level was relatively higher in tissues deficient in sugars than in those with high sugar levels. Observations of actin and tubulin cytoskeletons in cells of infected embryo axes cultured on the medium with sucrose, as well as the medium without sugar, showed significant differences in their organization

The Role of Saccharides in the Mechanisms of Pathogenicity of Fusarium oxysporum f. sp. lupini in Yellow Lupine (Lupinus luteus L.)

The primary aim of this study was to determine the relationship between soluble sugar levels (sucrose, glucose, or fructose) in yellow lupine embryo axes and the pathogenicity of the hemibiotrophic fungus Fusarium oxysporum f. sp. Schlecht lupini. The first step of this study was to determine the effect of exogenous saccharides on the growth and sporulation of F. oxysporum. The second one focused on estimating the levels of ergosterol as a fungal growth indicator in infected embryo axes cultured in vitro on sugar containing-medium or without it. The third aim of this study was to record the levels of the mycotoxin moniliformin as the most characteristic secondary metabolite of F. oxysporum in the infected embryo axes with the high sugar medium and without it. Additionally, morphometric measurements, i.e., the length and fresh weight of embryo axes, were done. The levels of ergosterol were the highest in infected embryo axes with a sugar deficit. At the same time, significant accumulation of the mycotoxin moniliformin was recorded in those tissues. Furthermore, it was found that the presence of sugars in water agar medium inhibited the sporulation of the pathogenic fungus F. oxysporum in relation to the control (sporulation of the pathogen on medium without sugar), the strongest inhibiting effect was observed in the case of glucose. Infection caused by F. oxysporum significantly limited the growth of embryo axes, but this effect was more visible on infected axes cultured under sugar deficiency than on the ones cultured with soluble sugars. The obtained results thus showed that high sugar levels may lead to reduced production of mycotoxins by F. oxysporum, limiting infection development and fusariosis