CLONING AND CHARACTERIZATION OF MS5 FROM ARABIDOPSIS - A GENE CRITICAL IN MALE MEIOSIS

In this paper, we describe the cloning of the MS5 gene, a gene essenti al for male fertility in Arabidopsis. We previously defined the MS5 lo cus by characterizing an EMS-induced allele, ms5-1. We identified a ne w allele of MS5 (ms5-2) that was T-DNA-generated and used the T-DNA ta g to clone the gene. Sequencing of mutant and wildtype alleles togethe r with complementation of the ms5-1 mutant phenotype with a wild-type genomic clone confirmed the identity of the gene. Differences between the phenotypes of the two mutant alleles could be attributed to differ ences in mutant gene structure. The semidominant and dominant negative phenotypes of the ms5-2 mutant probably result from production of a t runcated polypeptide. An unknown locus in Landsberg erecta can counter act the dominant negative phenotype of ms5-2. Mutations in MS5 cause t he formation of 'polyads' - tetrads with more than four pools of chrom osomes after male meiosis. Similarities between the MS5 sequence and t hat of a number of proteins were found; two that may be significant we re with a synaptonemal complex protein and with a regulatory subunit o f a cyclin dependent kinase. The MS5 gene is a member of a small gene family highly conserved amongst plant species.