Magnaporthe oryzae MTP1 gene encodes a type Ⅲ transmembrane protein involved in conidiation and conidial germination

In this study the MTP1 gene, encoding a type III integral transmembrane protein, was isolated from the rice blast fungus Magnaporthe oryzae. The Mtp 1 protein is 520 amino acids long and is comparable to the Ytp 1 protein of Saccharomyces cerevisiae with 46% sequence similarity. Prediction programs and MTP1-GFP （green fluorescent protein） fusion expression results indicate that Mtp 1 is a protein located at several membranes in the cytoplasm. The functions of the MTP1 gene in the growth and development of the fungus were studied using an MTP1 gene knockout mutant. The MTP1 gene was primarily expressed at the hyphal and conidial stages and is necessary for conidiation and conidial germination, but is not required for pathogenicity. The Amtpl mutant grew more efficiently than the wild type strain on non-fermentable carbon sources, implying that the MTP1 gene has a unique role in respiratory growth and carbon source use.

Effects of MEK-Specific Inhibitor U0126 on the Conidial Germination,Appressorium Production,and Pathogenicity of Setosphaeria turcica

Systemic studies on the effects of mitogen-activated protein kinase （MAPK） signal transduction pathway on the growth and development of Setosphaeria turcica is helpful not only in understanding the molecular mechanism of pathogenhost interaction but also in the effective control of the diseases caused by S. turcica. U0126, the specific MEK inhibitor, is used to treat S. turcica before the observation of the conidial germination, appressorium production, and pathogenicity of the pathogen. There is no significant effect of U0126 on the colony morphology and mycelium growth of the pathogen. After treatment with U0126, the growth of mycelium and conidia are normal, but the conidial germination, appressorium production, and pathogenicity of S. turcica on susceptible corn leaves are significantly inhibited. Under the definite concentration scope, an increase in U0126 concentration increases the inhibition degree of conidial germination and appressorium production, but the inhibition degree decreases with elongation of treatment time. The conidial germination, appressorium production, and pathogenicity of S. turcica on susceptible corn leaves are regulated by the MAPK pathway inhibited by U0126.

UvSMEK1,a Suppressor of MEK Null,Regulates Pathogenicity,Conidiation and Conidial Germination in Rice False Smut Fungus Ustilaginoidea virens

Rice false smut,which is caused by Ustilaginoidea virens,is an emerging disease of rice spikelets in rice-growing areas worldwide.However,the infection mechanism of U.virens on rice spikelets is still unclear.Here,we characterized a suppressor of mitogen-activated protein kinase kinase or ERK kinase(MEK)null(UvSMEKI)in U.virens that is conserved among filamentous fungi.Compared with wild type U.virens strain P-1,UvSMEKI deletion mutants were defective in pathogenicity and conidial germination.In addition,conidiation of UvSMEKI deletion mutants was significantly reduced on yeast extract tryptone(YT)plates,but inc「eased in YT broth compared with the wild type.Compared with UvSMEKI expression level during the vegetative mycelia and conidiation stages,UvSMEKI dramatically increased during infection of rice florets.Surprisingly,the UvSMEKI deletion mutants exhibited higher tolerance to H_(2)O_(2) and NaCl.In summary,presented evidence suggested that UvSMEKI positively regulated pathogenicity,conidial germination and conidiation in YT broth,and negatively regulated conidiation on YT medium and tolerance to oxidative and osmotic stresses.The results enhanee our understanding of the regulatory mechanism of pathogenicity of U.virens,and present a potential molecular target for blocking rice infection by U.virens.