Cloning and characterization ofMS5fromArabidopsis: a gene critical in male meiosis

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Abstract
In this paper, we describe the cloning of the MS5 gene, a gene essential for male fertility in Arabidopsis . We previously defined the MS5 locus by characterizing an EMS‐induced allele, ms5–1 . We identified a new allele of MS5 ( ms5–2 ) that was T‐DNA‐generated and used the T‐DNA tag to clone the gene. Sequencing of mutant and wild‐type alleles together 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 differences in mutant gene structure. The semi‐dominant and dominant negative phenotypes of the ms5–2 mutant probably result from production of a truncated polypeptide. An unknown locus in Landsberg erecta can counteract the dominant negative phenotype of ms5–2 . Mutations in MS5 cause the formation of ‘polyads’– tetrads with more than four pools of chromosomes after male meiosis. Similarities between the MS5 sequence and that of a number of proteins were found; two that may be significant were with a synaptonemal complex protein and with a regulatory subunit of a cyclin‐dependent kinase. The MS5 gene is a member of a small gene family highly conserved amongst plant species.