| Rice blast, caused by the ascomycete Magnaporthe oryzae, is one of the most devastating fungal diseases of rice worldwide. The new pathogenic groups and resistant groups appear because of easy variation of the pathogen races, which resulted in the loss of disease-resistant varieties of rice resistant and fungicides lose their effect. Consequently, the prevention and cure of Magnaporthe oryzae is always an important problem on rice production. An important prerequisite for specific new target for drug development is to understand the molecular mechanism of the growth and virulence of the pathogen.in recent years,identification and fuctional of analysis of pathogenesis related genes have been accelerated by the completion of rice blast fungus genome sequencing,which provides an experimental basis for the discovery of new drug targets.Sulfur, an essential element, plays an important role in biological growth and development, sulfur is an integral part of some amino acids which construct a number of biological macromolecules for the body, amino acids can not only provide nitrogen involved enzymes, hormones, vitamins, but also have a significant impact on biological metabolism; such as reduce the metal ions toxic effects for plant. All organisms can not survive apart from amino acids. Methionine is an essential amino acid containing sulfur, is an important component of proteins, but also can generate S-adenosylmethionine (SAM) involved in intracellular regulation of many physiological processes. Some key enzymes and regulatory factors in the biosynthesis of methionine can be used as a potential target for fungicides and antimicrobial drugs. METR in Aspergillus nidulans is a bZIP transcription factor with conserved leucine zipper structure and activate the transcriptional expression of sulfur metabolic genes involved in the synthesis of methionine. Methylenetetrahydrofolate reductase plays a key role in the final step of methionine biosynthesis, catalyzes the reduction of 5,10-methylenetetrahydrofolate (CH2-THF) to 5-methyltetrahydrofolate (CH3-THF), which is required for methionine biosynthesis. Most fungal species appear to have two MTHFR encoding genes, such as MET12 and MET13 in Saccharomyces cerevisiae. In this paper, we detailedly investigated the function of methionine biosynthesis pathway related gene MometR and MTHFR related genes during devemplent and pathogenesis in Magnaporthe oryzae.the results were as follows:We characterized a transcription factor MoMetR, a homolog of MetR in A. nidulans. Like AnMetR, MoMetR possesses a BRZL domain. To characterize the function of MoMetR in Magnaporthe oryzae, the MoMETR gene was disrupted and the mutant strain characterized. The △MometR mutant exhibited growth and conidial formation defects, which can be restored by exogenously adding methionine, but resulted in abnormal conidia. Disruption of MoMETR attenuated virulence which can partily be restored by exogenously adding methionine. The above results indicated that MoMetR not only participate in the methionine biosynthesis but also is required for conidium morphology and pathogenicity.MTHFR is a key enzyme in methionine biosynthetic pathway. To analysis the function of MoMET12 and MoMET13, the homolog of Saccharomyces cerevisiae ScMET12 and ScMET13, targeted genes were replaced by gene knock-out strategy and generated knock-out mutants △Momet12 and △Mometl3. Disruption of both genes resulted in defects in auxotrophic for methionine and conidial formation on SDC plates, the phenotype can be recoved by exogenously adding methionine. Which indicated that both genes involved in the process of methionine synthesis. Distruption of MoMET12 resulted in pathogenicity can be restored by exogenously adding methionine but can not be restored by distrupting of MoMET13.indicating that MoMET13 participates in the synthesis of methionine is also involved in rice blast fungus pathogenic process. |
PDF Full Text Request