Regional insertional mutagenesis of genes on Arabidopsis thaliana chromosome V using the Ac/Ds transposon in combination with a cDNA scanning method.

For regional insertional mutagenesis of Arabidopsis thaliana genes, we combined a cDNA scanning method (Hayashida et al. Gene 1995; 165:155-161) and an Ac/Ds transposon designed for local mutagenesis, and evaluated this approach with two overlapping yeast artificial chromosome (YAC) clones, CIC7E11 and CIC8B11, on A. thaliana chromosome 5. We applied a previously developed novel cDNA selection method using DNA latex particles (cDNA scanning method) to the two YAC clones and constructed two sub-libraries in which cDNAs for genes on each YAC DNA were concentrated. From each sub-library we isolated cDNAs for genes on each YAC DNA, partially sequenced them, and produced expressed sequence tags (ESTs). In total, 113 non-redundant groups of cDNAs were obtained. Forty-four per cent of these EST clones were novel, and 34% had significant homology to functional proteins from various organisms. In parallel, we transposed Ds from a donor Ds-GUS-T-DNA line, Ds4391-20, already mapped to the CIC7E11/8B11 region. We obtained Ds-transposed lines and recovered their Ds-flanking genomic DNAs by thermal asymmetric interlaced (TAIL) polymerase chain reaction (PCR). Dot-blot analysis indicated that 20% of the lines contained transposed Ds in the CIC7E11/8B11 region, suggesting that this Ac/Ds transposon system is effective for regional insertional mutagenesis. To isolate Ds insertion mutants in the genes identified from the CIC7E11/8B11 region, we carried out PCR screening from 800 Ds-containing lines using Ds-specific and gene-specific primers that were designed from the 113 cDNA sequences identified by the cDNA scanning method. We found that 49 lines contain Ds insertion mutations, and that five lines contain Ds mutations in genes that are mapped to the sequenced CIC7E11/8B11 genomic DNA region. These results indicate that combining the cDNA scanning method and the Ac/Ds transposon gives a powerful tool for regional insertional mutagenesis not only in Arabidopsis but also in other plants or crops whose genomes are not sequenced.