Abstract: A male sterile mutant, ms1142, was isolated from a population of ethyl methane sulfonate (EMS)-treated wild-type Arabidopsis thaliana. The mutant has small siliques with no seed set. Cytological observation showed that during anther development, the microspores ruptured and no pollen grains formed in the mutant anther locules. Scanning electron microscopy revealed an aberrant and broken microspore exine in the mutant. Genetic analysis indicated that the mutant is controlled by a single recessive nuclear gene. Map-based cloning mapped the mutant gene MS1142 to a region of 44 kb in BAC F16P17 on chromosome 1. Bioinformatics analysis revealed no previous male sterile gene cloned in this region, so MS1142 is a new gene involved in anther and pollen development. These results set the basis for cloning and functional analysis of this gene controlling anther development.