Parasitic differentiation of Claviceps purpurea

Shaw, Barbara I.; Mantle, Peter G.

doi:10.1016/s0007-1536(80)80201-4

Cited by 12 publications

(3 citation statements)

References 6 publications

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“…Ascospores, the primary inoculum, produced from overwintered sclerotia during the spring about the time of flowering in grasses (1,4,14), infect the grass ovaries. Honeydew, visible within one to two weeks after infection (7,13,17), attracts insects, especially flies and moths (5,9), which are presumed responsible for secondary spread of conidia. Infected ovaries are replaced with elongated black sclerotia, also referred to as ergot.…”

Section: Introductionmentioning

confidence: 99%

Timing of Occurrence of Claviceps purpurea Ascospores in Northeast Oregon

Alderman

Walenta

Hamm

2010

Plant Health Progress

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Ergot, caused by Claviceps purpurea, is an important floral disease of grasses, characterized by sclerotium formation within the host flowers. To determine whether annual variation in ergot severity in Kentucky bluegrass is a result of ascospore density and/or timing of ascospore occurrence, Burkard 7-day volumetric spores traps were used to monitor ascospores of C. purpurea in each of two Kentucky bluegrass fields in the Grand Ronde Valley in northeastern Oregon between mid-May and late June, 2008-2010. Ascospores were typically trapped between midnight and 6:00 a.m. In 2008 and 2010, most ascospores were released prior to flowering in Kentucky bluegrass, corresponding to no observed ergot in 2008 and a low level of ergot in 2010. In 2009, ascospore release and pollination coincided, but few airborne ascospores were present, resulting in a low level of ergot. Similar ergot levels were observed in fungicide trials, suggesting that fungicides for ergot control were unnecessary. In years when there are few ascospores during flowering in Kentucky bluegrass, a reduction of up to two fungicide applications may be possible. Accepted for publication 2 November 2010. Published 23 November 2010.

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Section: Introductionmentioning

confidence: 99%

Timing of Occurrence of Claviceps purpurea Ascospores in Northeast Oregon

Alderman

Walenta

Hamm

2010

Plant Health Progress

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“…The present finding of rye seedling stem apex susceptibility to C. purpurea inoculum, when introduced locally during early germination, demonstrates that the pathogen can parasitise any unprotected meristem-like tissue. Normally, during grass and cereal growth, the stem apex is inaccessible, leaving an unfertilised ovary as the only feasible port of entry, either via the stigma by mimicking pollen tubes or by direct penetration through the ovary wall [27,28]. Biochemical mechanisms for gentle avoidance of the host's wound reaction at the narrow ovary/rachilla junction, involving secretion of β-glucanase and pectinase, have been demonstrated experimentally [29].…”

Section: Discussionmentioning

confidence: 99%

Comparative Ergot Alkaloid Elaboration by Selected Plectenchymatic Mycelia of Claviceps purpurea through Sequential Cycles of Axenic Culture and Plant Parasitism

Mantle

2020

Biology

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Ergot alkaloids have an established place in plant pathology and toxicology. As pharmaceuticals, their sourcing is via natural or managed agricultural occurrence of sclerotia of Claviceps purpurea (Fr.) Tul. or through industrial fermentation processes with other Claviceps. The key factor for biosynthesis is differentiation of a particular mycelial anatomy. Previous study of these fungi from two disparate English grass genera, Spartina and Phragmites, has shown that only mycelia expressing a plectenchymatic sclerotium-like anatomy in specific axenic culture conditions elaborated ergot alkaloids, and then only as far as lysergic acid. The present report describes sequential cycles of axenic and parasitic cultivation for wild isolates from Dactylis and Alopecurus with intervention of a single ascospore step. This confirms the homozygous character of C. purpurea and defines several potential experimental axenic and parasitic conditions within the species for comparing genomic aspects of partial or full biosynthesis of cyclic tri-peptide alkaloids. Whereas Alopecurus ergot isolates readily parasitized rye, use of Dactylis isolates as inoculum for rye ovaries failed to cause the usual sphacelial fructification but supported growth of exceptionally thin sclerotia, sometimes two in a floret, with low alkaloid content attributed to reduced medullary component. However, after two cycles of axenic and rye-parasitic cultivation, and consistent re-selection of the plectenchymatic character in axenic mycelia, typical growth of ergot sclerotia occurred on rye. Caution thus seems necessary in tests for putative host specificity in any taxonomic realignments within the classical concept of C. purpurea. A Dactylis ergot isolate was also uniquely shown to parasitise the plumule of germinating rye seeds confirming the susceptibility of apical tissues. A key biosynthetic feature of a mycelial glyceride oil, rich in ricinoleic acid, as a prelude to axenic and parasitic formation of ergot alkaloids by C. purpurea is emphasised.

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“…Since ergot sclerotia grow acropetally, the youngest tissue will be found at the point of attachment with the host (Shaw & Mantle, 1980). Division of developing ergots of varying age Key : ---+ steps operating normally; ---+ , uncertain whether steps operate; 11, metabolic block ; --+, steps operating when appropriate substrates given ; ( ), theoretical intermediate, though undetected.…”

Section: R E S U L T Smentioning

confidence: 99%

Unusual Ergot Alkaloid Biosynthesis in Sclerotia of a Claviceps purpurea Mutant

1983

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A strain of Clauiceps purpurea, which has consistently failed to elaborate ergot alkaloids when growing as a parasite, has been shown to perform only the first step of the ergoline biosynthetic pathway catalysed by dimethylallyltryptophan (DMAT) synthetase. The next step, involving Nmethylation of DMAT, did not operate.[ 14C]Agroclavine and lysergic acid, normally intermediates in alkaloid biosynthesis, were accepted by parasitic sclerotial tissue as substrates and were metabolized to lysergic acid amide (LAA). This amide therefore constituted a previously unreported end product for C. purpurea. It is concluded that the mutant has a metabolic block in the pathway following DMAT and, while enzymes for several subsequent steps are present, the fungus seems unable to form the usual cyclic tripeptide ergot alkaloids. The steps involved in metabolizing agroclavine to LAA were insensitive to 1 M-phosphate, while this concentration of phosphate completely inhibited DMAT synthetase. This double mutant therefore has unique potential for exploring control mechanisms in ergot alkaloid biosynthesis.

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Parasitic differentiation of Claviceps purpurea

Cited by 12 publications

References 6 publications

Timing of Occurrence of Claviceps purpurea Ascospores in Northeast Oregon

Timing of Occurrence of Claviceps purpurea Ascospores in Northeast Oregon

Comparative Ergot Alkaloid Elaboration by Selected Plectenchymatic Mycelia of Claviceps purpurea through Sequential Cycles of Axenic Culture and Plant Parasitism

Unusual Ergot Alkaloid Biosynthesis in Sclerotia of a Claviceps purpurea Mutant

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