Characterization of genome-reduced fission yeast strains

The Schizosaccharomyces pombe genome is one of the smallest among the free-living eukaryotes. We further reduced the S. pombe gene number by large-scale gene deletion to identify a minimal gene set required for growth under laboratory conditions. The genome-reduced strain has four deletion regions: 168.4 kb in the left arm of chromosome I, 155.4 kb in the right arm of chromosome I, 211.7 kb in the left arm of chromosome II and 121.6 kb in the right arm of chromosome II. The deletions corres-ponded to a loss of 223 genes of the original 5100. The quadruple-deletion strain, with a total deletion size of 657.3 kb, showed a decreased ability to uptake glucose and some amino acids in compari-son with the parental strain. The strain also showed increased gene expression of the mating phero-mone M-factor precursor and the nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase. There was also a 2.7-fold increase in the concentration of cellular adenosine triphos-phate, and levels of the heterologous proteins, enhanced green fluorescent protein and secreted human growth hormone were increased by 1.7-and 1.8-fold, respectively. The transcriptome data from this study have been submitted to the Gene Expression Omnibus (GEO