Construction Of Transgenic Arabidopsis Thaliana Plants Expressing Phytophthora Infestans Avirulence Gene Avr-Blb1

Most oomycetes inflict their great damages on plants. The most notorious is Phytophthora infestans, the causal agent of potato late blight and the Irish potato famine in the middle of 1800's. The late blight disease of potato is still a damaging disease to date, costing over five billion dollars worldwide in crop losses and control expenses annually. The application of resistant cultivars is an important measure to control the disease. In the incompatible interaction between pathogens and resistant host plants, avirulence proteins of pathogens are specifically recognized by cognate plant resistant proteins, triggering hypersensitive response in plants to inhibit the growth of pathogen. Functional characterization of avirulence genes and discovery of the interaction machinery between Avr and resistant proteins will aid to develop novel approaches for Oomycete disease control. Although some data showed the Avr protein could be identified either directly or indirectly by their corresponding resistance proteins, more efforts need to be paid in understanding of the function of Avr proteins and the interaction mechanism of Avr and resistant proteins during infection.To deeply explore the characteristics of Avr-blb1 protein and the interaction mechanism between it and RB resistance protein, we construct transgenic Arabidopsis thaliana stably expressing ipiO1, which is one of the two members of Avr-blb1 gene family. Three types of ipiO1 gene were used: ipiO1 without the signal peptide sequence, ipiO1 with the signal peptide sequence of tobacco PR1a and the leaderless ipiO1 with six histidines tag. Transgenic A. thaliana with the mature ipiO1 and ipiO1 with tobacco signal peptide were challenged by Phytophthora parasitica to examine physiological and biochemical changes the ipiO1 gene may cause in the transgenic plants. The His-tagged ipiO1 transgenic A. thaliana will be used for cell biological investigation of ipiO1 protein inside plant cells.All transgenic lines were obtained through Agrobacterium tumefaciens- mediated transformation, and the positive transformants were screened out by RT-PCR and by inoculation of P. parasitica except the A. thaliana transformed with His-tagged ipiO1. Some transformants appeared more or less susceptible to P. parasitica, and the repeat test is under way. His-tagged ipiO1 and RB were coexpressed transiently in the leaves of Nicotiana benthamiana, and necrotic lesion was observed around infiltration site, indicating that the six histidines tag does not interfere the avirulence and possibly biological activities of ipiO1.