title: Quantitative assessment of in planta distribution of metabolic activity and gene expression of an endophytic fungus.
abstract: Using perennial ryegrass infected with an Acremonium transformant carrying the Escherichia coli beta-D-glucuronidase gene (gusA) (GUS system) under control of a constitutive promoter, we have developed methods for the quantitative extraction of endophyte-associated GUS activity from plant material. Fluorometric assays of these extracts allow quantitative assessment of the distribution of endophyte-associated GUS activity within single plants (tillers) with high resolution. Fluorescence microscopy with the dye Imagene Green can in addition visualize individual GUS-expressing hyphae. Since the transformant expresses the GUS gene constitutively, GUS activity can be used as an indicator of in planta endophyte metabolic activity. Using this approach we found that (i) the concentration of endophyte metabolic activity in plant tissue decreases with increasing plant size, (ii) approximately 70% of endophyte metabolic activity present in a plant is located in the leaf sheaths, (iii) basal-apical gradients and lateral (younger to older tissue) gradients of endophyte metabolic activity exist and (iv) basal-apical gradients are established early in leaf development. Our data suggest that the concentration of endophyte in each part of the plant is regulated so that a predetermined threshold of total endophyte activity per plant is not exceeded and a consistent distribution pattern is maintained.
authors.affiliation: Department of Microbiology and Genetics, Massey University,Palmerston North,New Zealand.
authors.forename: Scott
authors.initials: S
authors.lastname: Herd
authors.affiliation: AgResearch Grasslands,Palmerston North,New Zealand.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Christensen
authors.affiliation: AgResearch Grasslands,Palmerston North,New Zealand.
authors.forename: Karyn
authors.initials: K
authors.lastname: Saunders
authors.affiliation: Department of Microbiology and Genetics, Massey University,Palmerston North,New Zealand.
authors.forename: D Barry
authors.initials: DB
authors.lastname: Scott
authors.affiliation: Department of Microbiology and Genetics, Massey University,Palmerston North,New Zealand.
authors.forename: Jan
authors.initials: J
authors.lastname: Schmid
mesh_terms: D000164:Acremonium / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D005966:Glucuronidase / Q000096:biosynthesis* / Q000235:genetics; D008129:Lolium / Q000033:anatomy & histology / Q000201:enzymology* / Q000382:microbiology; D008856:Microscopy, Fluorescence; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D014170:Transformation, Genetic
chemical_list: D005966:Glucuronidase