GENOME-BASED STRATEGIES FOR DETECTION AND IDENTIFICATION OF PLANT PATHOGENIC PHYTOPLASMAS AND SPIROPLASMAS
Title: Transgene expression in pear (Pyrus communis L.) driven by a phloem-specific promoter
Submitted to: Acta Horticulturae Sinica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2008
Publication Date: April 1, 2008
Citation: Sun, Q., Sun, H., Zhao, Y., Hammond, R., Davis, R.E. 2008. Transgene expression in pear (Pyrus communis L.) driven by a phloem-specific promoter. Acta Horticulturae Sinica. 35:487-492.
Interpretive Summary: Pear is a nutrient-dense fruit high in fibers, low in calories, and rich in minerals and vitamins. While customer demand for pear remains high, pear production has often been suppressed by diseases caused by bacteria, viruses, and other pathogens, including those exclusively localized in vascular tissues (nutrition-transporting vessels) of affected plants. In a previous study, we conceived a novel strategy and devised a molecular tool to specifically deliver potential therapeutic agents to vascular tissues to combat vascular tissue-inhabiting pathogens. In the current study, we applied the concept and approach to mitigating pear diseases. As the implementation of the approach requires genetic manipulation of pear plants (a process called transformation and regeneration), we established optimal conditions for efficient transformation and regeneration of a pear cultivar. As a pilot study, we introduced a reporter gene into the genetically modified pear plants using the molecular tool we devised previously. Based on the expression patterns of the reporter molecule, we found that the introduced gene product was precisely delivered to places where the vascular tissue-inhabiting pathogens may live. The findings from the current study suggest that this genetic engineering approach has high potential for targeted delivery of therapeutic agents to control vascular diseases in pear. The progress in this study contributes to enhanced food security. The findings will be of great interest to research scientists and professionals in plant biotechnology and to regulatory agencies that set guidelines for conducting risk assessment of genetically modified organisms.
A gene expression cassette carrying ß-glucuronidase (uidA) reporter gene under the control of the promoter of the Arabidopsis sucrose-H+ symporter gene (AtSUC2) was introduced to pear plants via an Agrobacterium-mediated leaf-explant transformation procedure. Transgenic shoots were regenerated from initial transformed cells using a newly improved pear regeneration protocol, which involved a callus proliferation / shoot primordium induction phase and a shoot elongation phase. Polymerase chain reaction and DNA gel blot analyses confirmed the integration of the reporter gene into the genome of each transgenic pear line examined. Immunoblot assay indicated the presence, in the transgenic plants, of the transgene-expressed ß-glucuronidase. Histological GUS activity indicated that the reporter gene was expressed specifically in the phloem system of leaves, petioles, and roots of all transgenic pear lines.