Construction of a YAC Contig of 2 Megabases Around the MS1 Gene in Arabidopsis thaliana

The ms1 mutation of Arabidopsis thaliana causes male sterility by preventing the development of normal microspores in the developing anther. The gene is located on a region of chromosome 5 containing the RFLP markers g4111, g4560 and g21503. Using yeast artificial chromosome (YAC) libraries, we have constructed a contig of 38 YACs spanning approximately 2.1 megabases (approximately 2% of the genome) around MS1 and redefined the order of these RFLP markers. Chimeric YACs and repetitive DNA caused problems in chromosome 'walking'. A method for cloning YAC right ends by plasmid rescue was applied to arabidopsis. One YAC end contained a portion of the A. thaliana sucrose synthase gene ASUSI, hence locating this gene on chromosome 5 near MS1. Using recombinant plant populations containing ms1 and flanking markers, MS1 was localised to a 200 kb region within the YAC contig. In this contig the relationship between physical and genetic distance varied from less than 100 kb to 720 kb per centimorgan.