Effect of glutamic acid on the fatty acid and lipid composition of Choanephora cucurbitarum.

The fatty acid composition of the total, neutral, sterol, free fatty acid, and polar-lipid fractions in the mycelium of Choanephora curcurbitarum was determined. The major fatty acids in all lipid fractions were palmitic, oleic, linoleic, and gamma-linolenic acid. Different lipid fractions did not show any particular preference for any individual fatty acid; however, the degree of unsaturation was different in different lipid fractions. Free fatty acid and polar lipid fractions contained a higher proportion of gamma-linolenic acid than did triglyceride and sterol fractions. Addition of glutamic acid to the malt-yeast extract and medium resulted in the biosynthesis of a number of long-chain fatty acids beyond the gamma-linolenic acid. These fatty acids, e.g., C22:1, C24:0, and C26:0, were never observed to be present in the fungus when grown on a malt-yeast extract medium without glutamic acid. Furthermore, thin-layer chromatographic analysis showed a larger and denser spot of diphosphatidyl glycerol from the mycelium grown on glutamic acid medium than from the control mycelium. The possible significance of this finding is discussed.     

First Report of Choanephora Rot of Okra Caused by Choanephora cucurbitarum in Korea

In July and August 2013, blossom blight and soft rot of pods were observed on okra in experimental fields in Iksan and Jeju, Korea. Infection started in fading flower petals, spread to entire flowers and young pods, resulting in blighted blossoms and soft rot of pods. Severe infection caused early falling of blossoms and fruit drop, reducing plant vigour in the summer season. On the basis of the morphological characteristics and phylogenetic analyses of two molecular markers ITS rDNA and D1/D2 region of the LSU, the fungus was identified as Choanephora cucurbitarum. A pathogenicity test was carried out to fulfil Koch's postulates. To our knowledge, this is the first report of C. cucurbitarum on okra in Korea.     

Effect of variou cultural conditions on the fatty acid and lipid composition of Choanephora cucurbitarum.

The fatty acid composition of the total and polar lipid fractions of Choanephora cucurbitarum grown under different cultural conditions were analyzed by thin-layer and gas-liquid chromatography. It was observed that temperature, age, pH, and light influenced the degree of unsaturation, this being due mainly to changes in the gamma-linolenic acid concentration. The conditions used in this study did not alter the qualitative profile of fatty acids normally present in the organism. Neither did these conditions stimulate the production of further long-chain fatty acids (C20-C26) beyond gamma-linolenic acid (C18:3) as reported earlier using growth media containing glutamic acid. The fatty acid pattern of lipid fractions though the same qualitatively, differed quantitatively. The polar lipid fractions, phosphatidyl choline, phosphatidyl ethanolamine, and diphosphatidyl glycerol showed an appreciable variation in gamma-linolenic acid content under different cultural conditions. The degree of unsaturation of the various lipid fractions decreased with increases in temperature, light intensity, and pH, but within each treatment the same pattern of decreasing degree of unsaturation with increasing age was observed. The significance of these observations is discussed.     

An Inflorescence Disease of Amaranthus spp. in Nigeria Associated with Choanephora cucurbitarum

Abstract Symptoms of a devastating inflorescence disease of Amaranthus spp. associated with Choanephora cucurbitarum are described. It is characterized by extensive blighting of the inflorescence head and is often accompanied by inflorescence dieback and severe breaking of the floral head. In fields with severe infestation and under favourable conditions the inflorescence heads may be completely cut off. Such a plant will not produce any seeds or the yield may be reduced to half or less.
Laboratory experiments confirm observations made in the field that the fungus is aggressively pathogenic on the apical region of the inflorescence. Usually, the green young inflorescences are more susceptible.     

Factors Affecting Germination and the Mode of Germination of Zygospores of Choanephora cucurbitarum

Treatment of zygospores of Choanephora cucurbitarum with KMnO₄, NaClO or H₂O₂ effectively activated the spores and induced their germination. The optimum concentration of KMnO₄ for activation of zygospores was 0.25 to 0.5%. Zygospores were not able to germinate in darkness even after activation by KMnO₄. When zygospores from 40 to 50-day-old cultures were treated with 0.5% KMnO₄ solution for 60 min before incubation on water agar at 24% under light, about 50% germinated in 10 days. KMnO₄ treatment killed more than 99% of residual mycelial fragments, sporangiospores and sporangiola in the zygospore suspension. During germination disappearance of oil droplets in zygospores occurred prior to the cracking on zygospore wall. Both sporangial germination and mycelial germination were found. Moreover, sporangiole germination was observed for the first time.     

On the cell wall composition ofSaccharomycopsis guttulata

Summary Cells ofSaccharomycopsis guttulata were ruptured by sonic oscillation and the resulting cell walls were purified by washing and centrifugation. The walls contained 43.7% carbohydrate (expressed as glucose), 39.6% protein and a trace of chitin. Paper chromatography of hydrolyzed cell walls showed that glucose and an unknown reducing compound make up the bulk of the carbohydrate fraction. Mannose and glucosamine were present in small amounts. The cell wall composition ofS. guttulata appears to differ considerably from that ofS. cerevisiae.     

On the cell wall composition of the apiculate yeasts

Summary Sonic oscillation was used for the purpose of obtaining clean, chemically intact cell walls. The rate of disruption was determined for cells ofHanseniaspora uvarum andSaccharomyces cerevisiae. The carbohydrate fractions of cell walls ofHanseniaspora uvarum, H. valbyensis, Kloeckera apiculata, Saccharomycodes ludwigii andSaccharmyces cerevisiae were shown to be similar. Chromatography of cell wall hydrolysates of all these species demonstrated that glucose and mannose were the only sugars present (in about equal amounts) besides traces of glucosamine. The cell walls ofH. uvarum contained 78.1 per cent carbohydrates, 7 per cent protein and approximately 0.05 per cent of chitin. Fractionation of the polysaccharides lead to a recovery of 83.3 per cent of the carbohydrates present (30.4 per cent glucan and 34.9 per cent mannan). Saccharomyces cerevisiae cell walls were found to have a carbohydrate content of 82.8 per cent, 6.5 per cent protein and a trace of chitin (0.04 per cent). Nadsonia elongata contained a relatively large amount of chitin (ca. 5 per cent) and lacked mannan in its cell walls. It was concluded thatHanseniaspora andSaccharomycodes are closely related to theSaccharomyceteae but they have little in common with species ofNadsonia.     

Primary cell wall composition of bryophytes and charophytes

Major differences in primary cell wall (PCW) components between non-vascular plant taxa are reported. (1) Xyloglucan: driselase digestion yielded isoprimeverose (the diagnostic repeat unit of xyloglucan) from PCW-rich material of Anthoceros (a hornwort), mosses and both leafy and thalloid liverworts, as well as numerous vascular plants, showing xyloglucan to be a PCW component in all land plants tested. In contrast, charophycean green algae (Klebsormidium flaccidium, Coleochaete scutata and Chara corallina), thought to be closely related to land plants, did not contain xyloglucan. They did not yield isoprimeverose; additionally, charophyte material was not digestible with xyloglucan-specific endoglucanase or cellulase to give xyloglucan-derived oligosaccharides. (2) Uronic acids: acid hydrolysis of PCW-rich material from the charophytes, the hornwort, thalloid and leafy liverworts and a basal moss yielded higher concentrations of glucuronic acid than that from the remaining land plants including the less basal mosses and all vascular plants tested. Polysaccharides of the hornwort Anthoceros contained an unusual repeat-unit, glucuronic acid-alpha(1-->3)-galactose, not found in appreciable amounts in any other plants tested. Galacturonic acid was consistently the most abundant PCW uronic acid, but was present in higher concentrations in acid hydrolysates of bryophytes and charophytes than in those of any of the vascular plants. Mannuronic acid was not detected in any of the species surveyed. (3) Mannose: acid hydrolysis of charophyte and bryophyte PCW-rich material also yielded appreciably higher concentrations of mannose than are found in vascular plant PCWs. (4) Mixed-linkage glucan (MLG) was absent from all algae and bryophytes tested; however, upon digestion with licheninase, PCW-rich material from the alga Ulva lactuca and the leafy liverwort Lophocolea bidentata yielded penta- to decasaccharides, indicating the presence of MLG-related polysaccharides. Our results show that major evolutionary events are often associated with changes in PCW composition. In particular, the acquisition of xyloglucan may have been a pre-adaptive advantage that allowed colonization of land.     

The composition of the cell wall of Fusicoccum amygdali

1. The cell wall of Fusicoccum amygdali consisted of polysaccharides (85%), protein (4–6%), lipid (5%) and phosphorus (0.1%). 2. The main carbohydrate constituent was d-glucose; smaller amounts of d-glucosamine, d-galactose, d-mannose, l-rhamnose, xylose and arabinose were also identified, and 16 common amino acids were detected. 3. Chitin, which accounted for most of the cell-wall glucosamine, was isolated in an undegraded form by an enzymic method. Chitosan was not detected, but traces of glucosamine were found in alkali-soluble and water-soluble fractions. 4. Cell walls were stained dark blue by iodine and were attacked by α-amylase, with liberation of glucose, maltose and maltotriose, indicating the existence of chains of α-(1→4)-linked glucopyranose residues. 5. Glucose and gentiobiose were liberated from cell walls by the action of an exo-β-(1→3)-glucanase, giving evidence for both β-(1→3)- and β-(1→6)-glucopyranose linkages. 6. Incubation of cell walls with Helix pomatia digestive enzymes released glucose, N-acetyl-d-glucosamine and a non-diffusible fraction, containing most of the cell-wall galactose, mannose and rhamnose. Part of this fraction was released by incubating cell walls with Pronase; acid hydrolysis yielded galactose 6-phosphate and small amounts of mannose 6-phosphate and glucose 6-phosphate as well as other materials. Extracellular polysaccharides of a similar nature were isolated and may be formed by the action of lytic enzymes on the cell wall. 7. About 30% of the cell wall was resistant to the action of the H. pomatia digestive enzymes; the resistant fraction was shown to be a predominantly α-(1→3)-glucan. 8. Fractionation of the cell-wall complex with 1m-sodium hydroxide gave three principal glucan fractions: fraction BB had [α]_D +236° (in 1m-sodium hydroxide) and showed two components on sedimentation analysis; fraction AA₂ had [α]_D −71° (in 1m-sodium hydroxide) and contained predominantly β-linkages; fraction AA₁ had [α]_D +40° (in 1m-sodium hydroxide) and may contain both α- and β-linkages.