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Difluoromethylarginine (DFMA) and difluoromethylornithine (DFMO) are inhibitors of the polyamine biosynthetic enzymes arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), respectively. DFMO is a potential fungicide acting on fungal ODC. This report examines the effects of DFMA and DFMO on polyamine concentrations and metabolism, and on the activities of enzymes of polyamine biosynthesis and breakdown in the mycorrhizal fungus Laccaria proxima. Data indicate that L. proxima possesses both ADC and ODC activities. DFMA depleted putrescine and did not inhibit ODC activity, incubation of mycelium with a [U-14C]arginine substrate led to [14C]putrescine formation; DFMA completely inhibited the formation of polyamines from [U-14C]arginine; DFMO inhibited bound biosynthetic enzyme activity and the formation of putrescine from [U-14C]ornithine. Therefore, L. proxima may not be susceptible to fungicidal DFMO application. [ABSTRACT FROM AUTHOR]

Uptake of the polyamine biosynthesis inhibitor, α-difluoromethylornithine (DFMO), by barley seedlings was examined. DFMO was taken up by intact roots and approached saturation at a rate of 780 mol m-12 g-1 d.wt. The uptake as a function of DFMO concentration in the external medium was biphasic, with Eadie-Hofstee transformations giving Km values for system 1 uptake of 1.61 mol m-3 and for system 2 uptake of 53.31 mol m-3. DFMO uptake was reduced in darkness and was greatly influenced by transpiration rate. The inhibitor was taken up from host cells by the powdery mildew fungus, Erysiphe graminis f.sp. hordei Marchal, and DFMO fed to roots, or to excised leaves at different times after inoculation, gave substantial control of mildew infection. [ABSTRACT FROM AUTHOR]

summary: Growth and nutrient relations were examined in healthy leeks and in leeks inoculated with the rust, Puccinia allii, to give three different intensities of infection (i.e. 10, 20 and 30%). Experiments were conducted over an 8‐week experimental period, although only data from 5 weeks after inoculation are shown. The dry weights of rust‐infected plants were substantially reduced compared with controls over the entire experimental period. Although shoot: root (S: R) ratios were increased in rusted plants 2 weeks after inoculation, the trend was reversed thereafter and for the remainder of the experiment S:R ratio was reduced in comparison with healthy controls. The contents of nitrogen, phosphate, potassium and calcium were reduced in rusted plants compared to controls. On the other hand, with few exceptions, the concentrations and specific absorption rates of these minerals increased in rusted plants compared with healthy controls. The ability of infected plants to maintain a functional S:R equilibrium with respect to nutrient uptake was examined using an analysis based on comparing changes in incremental plant dry weight with incremental nutrient weight. Calculated values of functional equilibrium for control and rusted plants showed that rust infection altered functional equilibrium with respect to uptake of the four nutrients. The possible mechanisms underlying these changes in physiology and the analysis of such changes are discussed. [ABSTRACT FROM AUTHOR]

Photosynthesis was examined in discrete regions of leek (Allium porrum L.) leaves infected with the rust, Puccinia alli Rud. Oxygen evolution, expressed on both a chlorophyll and a leaf area basis, was significantly reduced in pustule regions, coupled with an increase in rates of dark respiration, for the duration of the experiment. The activity of ribulose bisphosphate carboxylase (RuBPcase) was reduced in pustule areas and losses in total soluble protein and chlorophyll were observed. Areas between pustules exhibited photosynthetic rates (on a chlorophyll basis) near to control values and dark respiration was reduced for at least part of the experiment. No significant alteration in RuBPcase activity, total soluble protein or chlorophyll concentrations was detected in interpustule regions. The physiological mechanisms underlying the changes in photosynthesis and respiration within discrete regions of rusted leeks are discussed. [ABSTRACT FROM AUTHOR]

The effects of the inhibitors of polyamine biosynthesis, 2-difluoromethylornithine (DFMO), (E)-2-(fluoromethyl) dehydroornithine (Δ-MFMO), (E)-2-(fluoromethyl) dehydroornithine methyl ester (Δ-MFMO CH3), 2-hydrazinoornithine, (2R,5R)-6-heptyne-2,5-diamine (RR-MAP), 2-difluoromethylarginine (DFMA), cyclohexylamine (CHA) and methylglyoxal-bis (guanylhydrazone) (MGBG) on infection of barley leaves (Hordeum vulgare L.) by Erysiphe graminis f.sp. hordei Marchal, were examined. Various concentrations of the inhibitors were sprayed onto barley leaves cv. Golden Promise as post-inoculation treatments. DFMO, MGBG and a combination of the two were also applied as pre-inoculation treatments. Each inhibitor substantially reduced mildew infection. DFMO was as efficient as the more recently developed ornithine analogues. With the exception of the DFMA treatments, post-inoculation sprays were more effective than pre-inoculation ones. When DFMO, MGBG and DFMA were sprayed onto leaves at different times, DFMO and MGBG most effectively controlled mildew when sprayed on the third day after inoculation. DFMA was more efficient as a pre-inoculation treatment. Addition of polyamines to DFMO sprays increased mildew infection, compared to that resulting from the DFMO treatment alone, but infection was less than in the controls. [ABSTRACT FROM AUTHOR]

The effects of the polyamine biosynthesis inhibitor, difluoromethylornithine (DFMO), on rust infection of the broad bean have been examined. DFMO was sprayed onto leaves at 0.025, 0.1 and 0.4 m[subM] before and after inoculation. DFMO was also applied to leaf halves in order to examine the possible translocation of the inhibitor to untreated leaf halves (systemic treatment). DFMO gave good control of rust infection, irrespective of the treatment. DFMO applied after inoculation was more effective than a pre-noculatory treatment when used in non-systemic tests. When used as a systemic treatment on leaf halves, pre-inoculatory application of DFMO was more effective. DFMO did not affect plant growth or endogenous concentrations of polyamines. The possible use of DFMO in the control of a range of plant diseases is discussed. [ABSTRACT FROM AUTHOR]

The concentrations of three amines (putrescine, spermidine and spermine) were much increased in first leaves of barley infected with powdery mildew, whilst the concentrations of putrescine and spermidine in roots of mildewed barley were significantly decreased. Although no significant change in the activities of three polyamine biosynthetic enzymes (ADC, arginine decarboxylase; ODC, ornithine decarboxylase; and SAMDC, S-adenosyl methionine decarboxylase) could be detected in roots of mildewed barley, the activities of ADC, ODC and SAMDC were increased in infected first leaves. The significance of these alterations in polyamines and their biosynthetic enzymes in mildewed barley is discussed. [ABSTRACT FROM AUTHOR]

The concentrations of three amines (putrescine, spermidine and spermine) are much increased in 'clubbed' regions of roots of turnip infected by Plasmodiophora brassicae, whilst the concentrations, particularly that of putrescine, decreased in regions of infected roots not exhibiting symptoms of clubroot development. The possible involvement of these polyamines in the formation of 'clubs' on infected roots is discussed. [ABSTRACT FROM AUTHOR]

Here, we examine the effect of saccharin on the induction of systemic resistance in broad bean (Vicia faba) to the rust fungus Uromyces viciae-fabae. Saccharin was applied to beans at the three-leaf stage, either as a soil drench or by painting the solution on to first leaves. Plants were then challenge inoculated with the rust 1, 6, 10 and 14 d following saccharin treatment, after which they were harvested, assessed for the intensity of rust infection and plant growth measurements conducted. Foliar application of saccharin did not induce systemic protection to rust infection until 14 d after application and was less effective than saccharin applied as a soil drench. When saccharin was applied as a drench, systemic protection was not observed until 6 d after application, but was still apparent in plants 14 d after application of the drench. Irrespective of the method of application, saccharin had no significant effect on fresh and dry weights or leaf area of the plants. Saccharin applied as a drench did, however, reduce the number of leaflets produced., (Copyright New Phytologist (2005).)

Although most work on polyamines in incompatible interactions between plants and pathogens has focussed on polyamines conjugated to phenolic compounds (hydroxycinnamic acid amides), changes in free polyamines and their catabolism have been shown to occur in such interactions. A common feature of these interactions is an increase in diamine oxidase (DAO) activity and, in some interactions, of polyamine oxidase (PAO). The activities of these two enzymes produces hydrogen peroxide (H 2 O 2 ), which may act in structural defense, as a signal molecule, or as an antimicrobial compound in host resistance. There are several possible roles for polyamines and polyamine catabolism in plant resistance to pathogen infection; H 2 O 2 produced might trigger the hypersensitive response (HR), thought to be a form of programmed cell death (PCD), the polyamine spermine might act as an inducer of PR proteins, and as a trigger for caspase activity and hence HR. There is, however, a need for more precise information on the timing and location of changes in polyamine metabolism in the development of resistance. Only with this information can a case be made for the involvement of polyamines and polyamine catabolism in plant defense.