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101.
Microbial synthesis of the phytohormone auxin has been known for a long time. This property is best documented for bacteria that interact with plants because bacterial auxin can cause interference with the many plant developmental processes regulated by auxin. Auxin biosynthesis in bacteria can occur via multiple pathways as has been observed in plants. There is also increasing evidence that indole-3-acetic acid (IAA), the major naturally occurring auxin, is a signaling molecule in microorganisms because IAA affects gene expression in some microorganisms. Therefore, IAA can act as a reciprocal signaling molecule in microbe-plant interactions. Interest in microbial synthesis of auxin is also increasing in yet another recently discovered property of auxin in Arabidopsis. Down-regulation of auxin signaling is part of the plant defense system against phytopathogenic bacteria. Exogenous application of auxin, e.g., produced by the pathogen, enhances susceptibility to the bacterial pathogen.The phytohormone auxin (from the Greek “auxein,” meaning to grow) regulates a whole repertoire of plant developmental processes, as documented in previous articles on this topic. Perhaps less well known is the fact that some microorganisms also produce auxin (Costacurta and Vanderleyden 1995; Patten and Glick 1996). In their interaction with plants, these microorganisms can interfere with plant development by disturbing the auxin balance in plants. This is best documented for phytopathogenic bacteria like Agrobacterium spp. and Pseudomonas savastanoi pv. savastanoi, causing tumors and galls, respectively (Jameson 2000; Mole et al. 2007), and plant growth promoting rhizobacteria (PGPR) such as Azospirillum spp. that impact on plant root development (Persello-Cartieaux et al. 2003; Spaepen et al. 2007a). The term rhizobacteria refers to the fact that their numbers are highly enriched in the rhizosphere, i.e., the narrow band of soil that surrounds the root (Hiltner 1904; Smalla et al. 2006; van Loon 2007). Of more recent date is the observation that auxin (indole-3-acetic acid or IAA) is a signaling molecule in some microorganisms (Spaepen et al. 2007a). Bringing these data together, it follows that auxin can have a major impact in microorganism-plant interactions. This is the main theme addressed in this article. Finally, the recent finding that auxin signaling in plants is also part of the Arabidopsis defense response against a leaf pathogen (Navarro et al. 2006) is discussed in relation to bacterial IAA synthesis. 相似文献
102.
Gillingwater K Gutierrez C Bridges A Wu H Deborggraeve S Ekangu RA Kumar A Ismail M Boykin D Brun R 《PloS one》2011,6(6):e20836
Three diamidines (DB 75, DB 867 and DB 1192) were selected and their ability to cure T. evansi experimentally infected goats was investigated. A toxicity assessment and pharmacokinetic analysis of these compounds were additionally carried out. Goats demonstrated no signs of acute toxicity, when treated with four doses of 1 mg/kg/day (total dose 4 mg/kg). Complete curative efficacy of experimentally infected goats was seen in the positive control group treated with diminazene at 5 mg/kg and in the DB 75 and DB 867 groups treated at 2.5 mg/kg. Drug treatment was administered once every second day for a total of seven days. Complete cure was also seen in the group of goats treated with DB 75 at 1.25 mg/kg. DB 1192 was incapable of curing goats at either four-times 2.5 mg/kg or 1.25 mg/kg. Pharmacokinetic analysis clearly demonstrated that the treatment failures of DB 1192 were due to sub-therapeutic compound levels in goat plasma, whilst compound levels for DB 75 and DB 867 remained well within the therapeutic window. In conclusion, two diamidine compounds (DB 75 and DB 867) presented comparable efficacy at lower doses than the standard drug diminazene and could be considered as potential clinical candidates against T. evansi infection. 相似文献
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104.
Daphne Kos Guy Nagels Marie B. D'Hooghe William Duquet Stephan Ilsbroukx Stijn Delbeke 《Chronobiology international》2013,30(2):345-356
Multiple sclerosis (MS) is a demyelinating disease resulting in impairments in motor and mental performance and restrictions in activities. Self‐report instruments are commonly used to measure activity patterns; alternatively, actigraphs can be placed on several parts of the body. The aims of this study were to evaluate the superiority and specificity of actigraph placement (wrist vs. ankle) in subjects with MS and healthy controls and explore the relationship between self‐report and objective activity patterns. A total of 19 subjects with definite MS and 10 healthy volunteers wore actigraphs on the non‐dominant wrist and ankle for three days while they kept a log to register performed activities every. 5 h. Wrist and ankle actigraphs produced similar activity patterns during the most active hours (09∶00–20∶30 h) (ANOVA, time×location interaction: F=.901, df=23, p=.597) in individuals with MS and healthy controls (between subjects factor F=3.275, p=.083). Wrist placement of the actigraphs was better tolerated than ankle placement. Wrist actigraph data corresponded to a higher degree with self‐reported activities of the upper limbs in the early afternoon, whereas ankle data seem to reflect better whole body movements in the later afternoon/early evening. Overall, actigraph data correlated moderately with self‐reported activity (r=.57 for ankle and r=.59 for wrist). The regression model revealed that self‐reported activities explained 44% of the variance in ankle and 50% of wrist data. Wrist and ankle actigraphs produce similar activity patterns in subjects with MS and in healthy controls; however, the placement of actigraphs on the wrist is better tolerated. Ankle actigraphs reflect general movement but underestimate upper body activity. Subjective registration of activity level partly matches with objective actigraph measurement. A combination of both objective and subjective activity registration is recommended to evaluate the physical activity pattern of subjects with MS. 相似文献
105.
Gitta Lasslop Stijn Hantson Sandy P. Harrison Dominique Bachelet Chantelle Burton Matthias Forkel Matthew Forrest Fang Li Joe R. Melton Chao Yue Sally Archibald Simon Scheiter Almut Arneth Thomas Hickler Stephen Sitch 《Global Change Biology》2020,26(9):5027-5041
In this study, we use simulations from seven global vegetation models to provide the first multi‐model estimate of fire impacts on global tree cover and the carbon cycle under current climate and anthropogenic land use conditions, averaged for the years 2001–2012. Fire globally reduces the tree covered area and vegetation carbon storage by 10%. Regionally, the effects are much stronger, up to 20% for certain latitudinal bands, and 17% in savanna regions. Global fire effects on total carbon storage and carbon turnover times are lower with the effect on gross primary productivity (GPP) close to 0. We find the strongest impacts of fire in savanna regions. Climatic conditions in regions with the highest burned area differ from regions with highest absolute fire impact, which are characterized by higher precipitation. Our estimates of fire‐induced vegetation change are lower than previous studies. We attribute these differences to different definitions of vegetation change and effects of anthropogenic land use, which were not considered in previous studies and decreases the impact of fire on tree cover. Accounting for fires significantly improves the spatial patterns of simulated tree cover, which demonstrates the need to represent fire in dynamic vegetation models. Based upon comparisons between models and observations, process understanding and representation in models, we assess a higher confidence in the fire impact on tree cover and vegetation carbon compared to GPP, total carbon storage and turnover times. We have higher confidence in the spatial patterns compared to the global totals of the simulated fire impact. As we used an ensemble of state‐of‐the‐art fire models, including effects of land use and the ensemble median or mean compares better to observational datasets than any individual model, we consider the here presented results to be the current best estimate of global fire effects on ecosystems. 相似文献
106.
Rob Moerkens Apostolos Pekas Stijn Bellinkx Inge Hanssen Marlies Huysmans Lien Bosmans Felix Wäckers 《Journal of Applied Entomology》2020,144(7):566-577
The use of Nesidiocoris tenuis (Hemiptera: Miridae) as a biocontrol agent is controversial as it is considered a pest in Northwest European tomato greenhouses, due to its tendency to damage the plant and fruit. Necessary chemical plant protection products to control N. tenuis have toxic side effects on important beneficials like Macrolophus pygmaeus (Hemiptera: Miridae), which jeopardizes the whole IPM programme. In this study, several commercial tomato greenhouses were monitored for mirid populations. The relationship between the number of N. tenuis individuals and plant damage was assessed in function of availability of prey and interaction with M. pygmaeus. These greenhouse data were used to determine a practical density intervention threshold. Next, the hypothesis that a Pepino mosaic virus (PepMV) infection increases plant and fruit damage by N. tenuis (as has been shown for M. pygmaeus) was tested. Plant damage occurred when the average number of predatory bugs in the head of the plant exceeded 16 per ten plants. Plant damage increased in severity at increasing predatory bug densities, independent of the availability of prey and M. pygmaeus presence. Plant and fruit damage were not affected by the presence of PepMV, as was shown for fruit damage in previous studies for M. pygmaeus. Our study provides a practical density intervention threshold for growers in greenhouse crops. Simple monitoring of the number of predatory bugs in the head of the plant can be used to take specific biocontrol actions. It was also shown that only the predatory bug N. tenuis itself causes damage, and there is no interaction with PepMV. 相似文献
107.
Versées W Spaepen S Wood MD Leeper FJ Vanderleyden J Steyaert J 《The Journal of biological chemistry》2007,282(48):35269-35278
Thiamine diphosphate-dependent enzymes are involved in a wide variety of metabolic pathways. The molecular mechanism behind active site communication and substrate activation, observed in some of these enzymes, has since long been an area of debate. Here, we report the crystal structures of a phenylpyruvate decarboxylase in complex with its substrates and a covalent reaction intermediate analogue. These structures reveal the regulatory site and unveil the mechanism of allosteric substrate activation. This signal transduction relies on quaternary structure reorganizations, domain rotations, and a pathway of local conformational changes that are relayed from the regulatory site to the active site. The current findings thus uncover the molecular mechanism by which the binding of a substrate in the regulatory site is linked to the mounting of the catalytic machinery in the active site in this thiamine diphosphate-dependent enzyme. 相似文献
108.
Sbastien R. Mouchet Charlotte Verstraete Anna M. Kaczmarek Dimitrije Mara Stijn van Cleuvenbergen Rik Van Deun Thierry Verbiest Bjorn Maes Pete Vukusic Branko Kolaric 《Journal of biophotonics》2019,12(9)
The wings of some insect species are known to fluoresce under illumination by ultraviolet light. Their fluorescence properties are however, not comprehensively documented. In this article, the optical properties of one specific insect, the Trictenotoma childreni yellow longhorn beetle, were investigated using both linear and nonlinear optical (NLO) methods, including one‐ and two‐photon fluorescence and second harmonic generation (SHG). These three distinct optical signals discovered in this beetle are attributed to the presence of fluorophores embedded within the scales covering their elytra. Experimental evidence collected in this study indicates that the fluorophores are non‐centrosymmetric, a fundamental requirement for SHG. This study is the first reported optical behavior of this type in insects. We described how NLO techniques can complement other more convenient approaches to achieve a more comprehensive understanding of insect scales and integument properties. 相似文献
109.
110.
Stijn Dhondt Nathalie Gonzalez Jonas Blomme Liesbeth De Milde Twiggy Van Daele Dirk Van Akoleyen Veronique Storme Frederik Coppens Gerrit T.S. Beemster Dirk Inzé 《The Plant journal : for cell and molecular biology》2014,80(1):172-184
Although quantitative characterization of growth phenotypes is of key importance for the understanding of essential networks driving plant growth, the majority of growth‐related genes are still being identified based on qualitative visual observations and/or single‐endpoint quantitative measurements. We developed an in vitro growth imaging system (IGIS) to perform time‐resolved analysis of rosette growth. In this system, Arabidopsis plants are grown in Petri dishes mounted on a rotating disk, and images of each plate are taken on an hourly basis. Automated image analysis was developed in order to obtain several growth‐related parameters, such as projected rosette area, rosette relative growth rate, compactness and stockiness, over time. To illustrate the use of the platform and the resulting data, we present the results for the growth response of Col–0 plants subjected to three mild stress conditions. Although the reduction in rosette area was relatively similar at 19 days after stratification, the time‐lapse analysis demonstrated that plants react differently to salt, osmotic and oxidative stress. The rosette area was altered at various time points during development, and leaf movement and shape parameters were also affected differently. We also used the IGIS to analyze in detail the growth behavior of mutants with enhanced leaf size. Analysis of several growth‐related parameters over time in these mutants revealed several specificities in growth behavior, underlining the high complexity of leaf growth coordination. These results demonstrate that time‐resolved imaging of in vitro rosette growth generates a better understanding of growth phenotypes than endpoint measurements. 相似文献