Fiona Ruth Murray

The role of GAMYB transcription factors in GA-regulated gene expression

A gibberellin- and abscisic acid-regulated MYB, GAMYB, was first identified as an activator of GA-regulated genes in cereal aleurone. Here we review recent advances made in delineating the signaling events related to GAMYB expression and function in aleurone. In addition, there is a growing body of evidence that GAMYB plays an important role in other aspects of plant growth and development, including anther development, stem elongation, floral initiation and seed development.

Comparison of Agrobacterium-mediated transformation of four barley cultivars using the GFP and GUS reporter genes

Experiments were conducted to produce transgenic barley plants following infection of immature embryos with Agrobacterium tumefaciens. Transformed callus was obtained using hygromycin resistance as a selectable marker and either green fluorescent protein (GFP) or β-glucuronidase (GUS) as a reporter. Significantly reduced plant transformation frequencies were obtained with the GFP gene compared to GUS. However, GFP proved to be an excellent reporter of early transformation events and was used to compare four barley cultivars for efficiency in two phases of transformation: the generation of stably transformed barley callus and the regeneration of plantlets from transformed callus. Transformed callus was generated at a high frequency (47–76%) in all four cultivars. Regeneration of transformed plantlets was also achieved for all four cultivars although the frequency was much higher for Golden Promise than for the other three genotypes, reiterating that genotype is an important determinant in the regenerative ability of barley. This study has demonstrated for the first time that Agrobacterium-mediated transformation can be used to transform the Australian cultivars Sloop and Chebec.

Comparison of three selectable marker genes for transformation of wheat by microprojectile bombardment

Three selectable marker genes were compared for their efficacy in the production of transgenic wheat plants following microprojectile bombardment of cultured immature embryos. While transformed plants were recovered using the bar (phosphinothricin acetyltransferase) gene in combination with bialaphos, and the aphA (neomycin phosphotransferase) gene in combination with geneticin or paromomycin, no transgenic material was obtained with the hpt (hygromycin phosphotransferase) gene and hygromycin B. Southern analysis revealed single copy as well as multiple copy insertions of the bar and aphA transgenes. Inheritance of these selectable marker genes was demonstrated in the T1 generation progenies.

Induction of Cell Death in Transgenic Plants Expressing a Fungal Glucose Oxidase

Hydrogen peroxide (H2O2) has been implicated in the induction of plant defense genes and programmed cell death. Expression of a chimeric fungal glucose oxidase (GO) gene driven by a pathogen- and wound-inducible promoter was evaluated in transgenic tobacco and canola as a possible tool for engineering plant cell death and defense gene induction. Expression of this gene under the control of a peroxidase gene promoter resulted in the accumulation of relatively low levels of H2O2 in the young leaves of transgenic tobacco plants and this was not sufficient to cause any visible cell death and defense gene induction as measured by PR-1a mRNA induction. Older leaves of transgenic tobacco plants, however, exhibited visible necrotic lesions and constitutively expressed PR-1a mRNA when grown under high light conditions. Inoculation of cotyledons of control and transgenic canola with Leptosphaeria maculans resulted in rapid cotyledon senescence in the transgenic plants. Strong activators of the peroxidase promoter, ...

Isolation of the glucose oxidase gene from Talaromyces flavus and characterisation of its role in the biocontrol of Verticillium dahliae.

Abstract The glucose oxidase gene from the biocontrol fungus Talaromyces flavus has been isolated and shown to be only 64% identical at the amino-acid sequence level to the similar enzyme from Aspergillus niger. A transformation system has been developed for both T. flavus and the related T. macrosporus and has been used to create Talaromyces spp. which either over-express or are deficient in glucose oxidase. In vitro inhibition experiments on Verticillium dahliae using culture filtrates from these transformants indicates that secreted glucose oxidase is responsible for a large part of the growth inhibition of V. dahliae microsclerotia and hyphae by T. flavus, although other inhibitory compounds may also play a role. In pot trials with cotton plants, both Talaromyces species had some biocontrol activity, but there was no significant difference in the incidence of Verticillium wilt with either the presence or absence of glucose oxidase activity in the biocontrol fungus. Under the experimental conditions used, insufficient glucose is presumably present in the soil around cotton roots to generate sufficient hydrogen peroxide to inhibit V. dahliae and the observed biocontrol activity must be attributed to other factors.