In this study the MTP1 gene, encoding a type Ⅲ integral transmembrane protein, was isolated fiom the rice blast fungus Magnaporthe oryzae. The Mtpl protein is 520 amino acids long and is comparable to the Ytpl protein of Saccharomyces cerevisiae with 46% sequence similarity. Prediction programs and MTP1-GFP (green fluorescent protein) fusion expression results indicate that Mtpl 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 ex-pressed at the hyphal and conidial stages and is necessary for conidiation and conidial germination, but is not required for patho-genicity. The △mtpl 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.