Comparison of cytokinin productionin vitrobyPyrenopeziza brassicaewith other plant pathogens

Murphy, Alex M.; Pryce-Jones, E; Johnstone, Keith; Ashby, Alison M.

doi:10.1006/pmpp.1996.0070

Cited by 41 publications

(33 citation statements)

References 33 publications

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“…Different fungi, both pathogenic or symbiotic, have been reported to produce CKs (Crafts and Miller, 1974; Murphy et al, 1997; Jameson, 2000; Chanclud and Morel, 2016). We have shown that L. maculans produces a wide spectrum of CKs in vitro , present both in the mycelium ( Figure 1 ) and culture medium (Supplementary Figure 1), as well as in planta upon infection in B. napus ( Table 1 ).…”

Section: Discussionmentioning

confidence: 99%

Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase

et al. 2017

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Among phytohormones, cytokinins (CKs) play an important role in controlling crucial aspects of plant development. Not only plants but also diverse microorganisms are able to produce phytohormones, including CKs, though knowledge concerning their biosynthesis and metabolism is still limited. In this work we demonstrate that the fungus Leptosphaeria maculans, a hemi-biotrophic pathogen of oilseed rape (Brassica napus), causing one of the most damaging diseases of this crop, is able to modify the CK profile in infected B. napus tissues, as well as produce a wide range of CKs in vitro, with the cis-zeatin derivatives predominating. The endogenous CK spectrum of L. maculans in vitro consists mainly of free CK bases, as opposed to plants, where other CK forms are mostly more abundant. Using functional genomics, enzymatic and feeding assays with CK bases supplied to culture media, we show that L. maculans contains a functional: (i) isopentenyltransferase (IPT) involved in cZ production; (ii) adenosine kinase (AK) involved in phosphorylation of CK ribosides to nucleotides; and (iii) CK-degradation enzyme cytokinin oxidase/dehydrogenase (CKX). Our data further indicate the presence of cis–trans isomerase, zeatin O-glucosyltransferase(s) and N6-(Δ2-isopentenyl)adenine hydroxylating enzyme. Besides, we report on a crucial role of LmAK for L. maculans fitness and virulence. Altogether, in this study we characterize in detail the CK metabolism of the filamentous fungi L. maculans and report its two novel components, the CKX and CK-related AK activities, according to our knowledge for the first time in the fungal kingdom. Based on these findings, we propose a model illustrating CK metabolism pathways in L. maculans.

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Section: Discussionmentioning

confidence: 99%

Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase

et al. 2017

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“…Other possible functions could include the degradation of host signal proteins involved in the HR or the release of nutrients from the apoplast through the degradation of host cell wall or membrane proteins (Ball et al 1991;Ashby 1997). Cytokinins have been implicated in the pathogenicity of P. brassicae to B. napus, with a possible role in mediating the provision of nutrients to the fungus through the alteration of host metabolism and diversion of nutrients to the site of infection, although it is unclear whether P. brassicae utilises plant-derived cytokinins or synthesises them de novo (Ashby 1997(Ashby , 2000Murphy et al 1997). An involvement of cytokinins in defence against free radicals, therefore limiting processes that contribute to the HR, has also been proposed (Beckman and Ingram 1994;Ashby 2000).…”

Section: Potential Resistance Mechanisms: Insights From Light Leaf Spmentioning

confidence: 99%

Resistance to infection by stealth: Brassica napus (winter oilseed rape) and Pyrenopeziza brassicae (light leaf spot)

et al. 2007

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Light leaf spot (Pyrenopeziza brassicae)is an important disease on winter oilseed rape crops (Brassica napus) in northern Europe. In regions where economically damaging epidemics occur, resistance to P. brassicae in commercial cultivars is generally insufficient to control the disease without the use of fungicides. Two major genes for resistance have been identified in seedling experiments, which may operate by decreasing colonisation of B. napus leaf tissues and P. brassicae sporulation. Much of the resistance present in current commercial cultivars is thought to be minor gene-mediated and, in crops, disease escape and tolerance also operate. The subtle strategy of the pathogen means that early colonisation of host tissues is asymptomatic, so a range of techniques and molecular tools is required to investigate mechanisms of resistance. Whilst resistance of new cultivars needs to be assessed in field experiments where they are exposed to populations of P. brassicae under natural conditions, such experiments provide little insight into components of resistance. Genetic components are best assessed in controlled environment experiments with single spore (genetically fixed) P. brassicae isolates. Data for cultivars used in the UK Recommended List trials over several seasons demonstrate how the efficacy of cultivar resistance can be reduced when they are deployed on a widespread scale. There is a need to improve understanding of the components of resistance to P. brassicae to guide the development of breeding and deployment strategies for sustainable management of resistance to P. brassicae in Europe.

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“…In other plant pathogenic fungi cytokinins are produced during plant infection to delay senescence and to allow the colonization of healthy plant tissue by the fungus (reviewed in Ashby, 2000 andMcRoberts, 2006;Gan and Amasino, 1995;Murphy et al, 1997). Accordingly, fusatin could play a similar role in F. pseudograminearum during wheat infection and suppress host cell death to allow the spread of the fungus in the still healthy plant tissue before the fungus switches to the necrotrophic infection phase during which DON production is potentially induced to kill the plant cells.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, locally increased cytokinin levels in plants infected with the biotrophic rust and powdery mildew fungal plant pathogens delay senescence of the infected leaves which leads to the formation of green islands, though it is not known yet if the fungi produce the cytokinins themselves, or the host metabolism is altered to induce localized cytokinin production in the plant (reviewed in Ashby, 2000 andMcRoberts, 2006). The hemibiotrophic fungus Pyrenopeziza brassicae produces cytokinins which might suppress host cell death during brassica infection to allow the colonization of healthy tissue (Gan and Amasino, 1995;Murphy et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Regulation and cell biology of secondary metabolite production in Fusarium graminearum and Fusarium pseudograminearum

Blum¹

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1 AbstractAscomycete fungi have the potential to produce a vast array of secondary metabolites, which are metabolites not required for normal growth and development. In any one species there is typically the potential for production of upward of fifty of these compounds. Many fungal secondary metabolites are used as medicines (e.g. penicillin or cyclosporine), or are of importance due to their toxicity in humans or animals (e.g. aflatoxins), or because they are virulence factors during crop plant infection (e.g. deoxynivalenol). Despite the vast potential encoded in ascomycete genomes, the vast majority of fungal secondary metabolites are yet to be discovered. This is in part due to our lack of understanding of how the production of these compounds is regulated. Moreover, even for the compounds we do know, we are just beginning to understand the complex interaction of external stimuli, signalling pathways, cellular and developmental biology that leads to their production. In this thesis, biological insights into these aspects of two fungal secondary metabolites, deoxynivalenol (DON) and fusatin are provided.In chapter II a high-throughput fluorescence activated cell sorting (FACS) based mutant screen was developed and the regulation of DON production in Fusarium graminearum was analysed. DON is an economically very important mycotoxin, as it is the most common contaminant of wheat, barley and corn worldwide. It is produced by plant pathogenic filamentous fungi of the Fusarium family, which can cause Fusarium head blight as well as Fusarium crown rot. During plant infection, DON is an important virulence factor and it can be toxic for humans and animals. The regulation of DON production is not yet fully understood. To identify regulators, a mutant screen was developed using FACS to allow high throughput screening, coupled with whole genome sequencing to identify mutations.Segregation analyses were performed to determine the mutation causing the phenotype.The mutant screen identified an adenylyl cyclase allele, which resulted in production of DON under normally repressive conditions. In addition, the mutant developed cellular structures associated with toxin production under repressive conditions. The levels of the fundamental second messenger cAMP, which adenylyl cyclases produce, were increased in the identified mutant, suggesting it might be a gain-of-function adenylyl cyclase mutant. This mutant screening methodology can be adapted to identify regulators of different secondary metabolites as well as to identify mutants overproducing yet unknown secondary metabolites. Abstract 2In chapter III the cell biology of DON production in Fusarium graminearum was elucidated with quantitative super resolution microscopy. During the last five years the first insights into the cell biology of DON production were gained, indicating complex cell biological mechanisms. During toxin production, F. graminearum develops endoplasmic reticulum proliferations, called toxisomes, at which two DON biosynthesis enzymes, TRI1 a...

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Comparison of cytokinin productionin vitrobyPyrenopeziza brassicaewith other plant pathogens

Cited by 41 publications

References 33 publications

Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase

Cytokinin Metabolism of Pathogenic Fungus Leptosphaeria maculans Involves Isopentenyltransferase, Adenosine Kinase and Cytokinin Oxidase/Dehydrogenase

Resistance to infection by stealth: Brassica napus (winter oilseed rape) and Pyrenopeziza brassicae (light leaf spot)

Regulation and cell biology of secondary metabolite production in Fusarium graminearum and Fusarium pseudograminearum

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