The biology of mycorrhiza in the Ericaceae

SUMMARYA yj-l,4-endoxylanase from the ericoid mycorrhizal fungus H. ericae has been purified to electrophoretic homogeneity using isoelectric focusing, ion exchange and gel permeation chromatography. The enzyme has an isoelectric point of 4-85-5-20 and a molecular weight of 58-4 kDa. The apparent S^.^ of the enzyme for soluble birchwood glucuronoxylan is 375 mg ml'^ and the V^^^ 468-0 nkatal mg"* protein. The pH optimum for activity is 4-5 and that for stability is 3-5^-O; these values are discussed in the context of the pH of the mor humus. The role of wall-degrading activities in the establishment of the ericoid mycorrhizal symbiosis is considered.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Purification and characterization of a β‐1,4‐endoxylanase from the ericoid mycorrhizal fungus Hymenoscyphus ericae

Burke

Cairney

1997

“…Previous work has shown that ericoid mycorrhizas can use protein as an N source by excretion of protease into the medium (Leake & Read, 1989). Ames et al (1984) demonstrated that AM-colonized sorghum (Sorghum bicolor) can use an organic source of N, although no protease excretion has been found in AM symbiosis.…”

Section: Discvssionmentioning

confidence: 99%

Effect of the arbuscular mycorrhizal fungus Glomus fasciculatum on the uptake of amino nitrogen by Lolium perenne

Cliquet

Murray²,

Boucaud

1997

SUMMARYThe ability of ryegrass (Loliumperenne h.) to take up and utilize aspartic acid (Asp) and serine fSer), and the effect of colonization of the roots by the arbuscular mycorrhizal (AM) fungus Glomus fasciculatum (Thas. sensu Gerd.) were studied. The seedlings were grown under controlled conditions in a series of micro-lysimeters. All plants were fed with a nutrient solution containing either nitrate, Asp or Ser as the sole N source. After 49 d, they were supplied with ^'N labelled nitrate. Asp or Ser for 1 h and har\'ested.AM colonization increased the growth and total N content of the plants in all cases. Similarly, the amount of Asp or Ser taken up was higher in AM than in control plants. There were no differences in biomass production between the nitrate and Ser-fed plants, However uptake rates were lower for Ser than for nitrate. Growth of the Asp-fed plants was significantly less than the other two treatments, and uptake of "N-Asp was lower than uptake of '"N-Ser. Analysis of '•''N incorporation into the amino acids extracted from the roots suggests the hydrolysis of Ser followed by re-assimilation of the resulting ammonia \ia the GS-GOGAT cycle. There were no differences in the patterns of accumulation of amino acids in the root-zone of control and AM-ryegrass. The implication of these results for the pathway of nitrogen transfer between plants is discussed.

“…1 paper, and the mycelium was then oven dried at 80 °C for 24 h and weighed. The culture filtrate was assayed for extracellular proteinase activity using an adaptation of the casein-fluorescein isothiocyanate (casein-FITC) method of Twining (1984), as described by Leake & Read (1989).…”

Section: Assay Of Enzyme Activitymentioning

confidence: 99%

“…However, the extracellular proteinase produced by cultures of H. ericae grown at pH 3-5 with bovine serum albumin (BSA) as sole N source has a well-defined, extremely acidic pH optimum at pH 2-2, with negligible activity at pH values of 4-0 and above (Leake & Read, 1989). On the basis of these observations, it has been suggested (Leake & Read, 1989) that the responses to pH reported by Bajwa et al (1985) represent the combined effect of pH on enzyme production and activity.…”

Section: Introductionmentioning

confidence: 99%

Proteinase activity in mycorrhizal fungi

Leake

Read

1990

Self Cite

SUMMARYThe effect of pH on the production and specific activity of tbe extracellular proteinase enzymes of two ecologically distinct ericoid mycorrhizal fungi is described. Tbe proteinase of Hymenoscyphus ericae (Read), Korf & Kernan, isolated from roots of Calluna vulgaris (L.) Hull growing in soil of pH 35, was compared with a similar enzyme from an endopbyte of tbe calcicolous alpine sbrub Rhodothamnus chamaecistus (L.) Reicbenb. growing in soil of pH 6-5. Tbe fungi were grown in liquid culture at pH values ranging from 3-0 to 8-0 witb pure protein, bovine serum albumin, as sole source of N.Botb fungi yielded an extracellular acid proteinase witb pH optimum for activity between 20 and 3-0. Tbe production and activity of tbese enzymes was strongly affected by pH of tbe culture medium. Maximum enzyme production during exponential growtb occurred in botb fungi at a culture pH of 40-50, wbereas bigber pH treatments severely inbibited enzyme production.Tbe acid proteinase of H. ericae was tolerant of extreme acidity and retained near-optimal activity in solutions of pH 2-0. In contrast, tbe activity of tbe enzyme from tbe Rhodothamnus endopbyte was almost completely inbibited at tbis pH. However, proteinase from tbe Rhodothamnus endopbyte retained activity at mucb bigber pH values tban did tbe proteinase from H. ericae. Unlike H. ericae, tbe isolated endopbyte of Rhodothamnus was able to grow and use protein as sole source of N at pH 7-0 and 8 0.Tbe effects of pH on enzyme production and upon growtb of tbe fungi are discussed in relation to tbe cbaracteristics of tbe environments of tbeir bost plants.