Functional analysis of mitogen-activated protein kinases from Phytophthora parasitica
Date Issued
2006
Date
2006
Author(s)
Huang, Chien-Yu
DOI
zh-TW
Abstract
Phytophthora parasitica Dastur (=P. nitcotianae Breda de Haan) is an Oomycete plant pathogen which causes severe disease in many economically improtant crops. According to “List of plant diseases in Taiwan”, there were at least 49 records of the plant diseases caused by P. parasitica. Since P. parasitica is an important plant pathogen, we are interested in the signal transduction mechanism of P. parasitica. Mitogen-activated protein kinase (MAP kinase) pathways operate at the core of eukaryotic signal transduction networks, and their component kinases have been highly conserved through evolution. Four MAP kinases that are homologous to fungal MAP kinases were cloned from P. parasitica and designated as ppmk1a, ppmk1b, ppmk2, and ppmk3, respectively. In order to investigate their roles, expression of these genes in different life stages of P. parasitica was analyzed by real-time quantitative reverse transcriptase-PCR. The results indicated expressions of all four genes were induced in the process of plant infection, while ppmk2 were expressed only in the stage of sporangia. Moreover, while expression of ppmk2 was induced in response to acidic pH and osmotic stress, ppmk3 was induced in response to osmotic stress, high concentration of cAMP and specific carbon sources including sorbitol, glycerol and pectin. It was thus suggested that ppmk2 and ppmk3 were involved in the signaling pathways of P. parasitica in response to different environmental signals. To analyze the kinase activity of these MAPKs, in vitro kinase assay was performed using recombinant proteins obtained from E. coli. The result indicated that Ppmk3 exhibited kinase activity toward an exogenous substrate. Furthermore, yeast two-hybrid system was employed to screen genes which might interact with ppmk1a, ppmk1b, ppmk2 or ppmk3. Putative functions of proteins encoded by these genes will be discussed. In order to know the function and regulatory mechanism of the MAP kinase signaling pathways, I have also tried to establish a transformation method for P. parasitica.
Subjects
疫病菌
訊息傳導
Phytophthora
MAPK
Type
other
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