SummaryInduction of knockout mutations by T‐DNA insertion mutagenesis is widely used in studies of plant gene functions. To assess the efficiency of this genetic approach, we have sequenced PCR amplified junctions of 1000 T‐DNA insertions and analysed their distribution in the Arabidopsis genome. Map positions of 973 tags could be determined unequivocally, indicating that the majority of T‐DNA insertions landed in chromosomal domains of high gene density. Only 4.7% of insertions were found in interspersed, centromeric, telomeric and rDNA repeats, whereas 0.6% of sequenced tags identified chromosomally integrated segments of organellar DNAs. 35.4% of T‐DNAs were localized in intervals flanked by ATG and stop codons of predicted genes, showing a distribution of 62.2% in exons and 37.8% in introns. The frequency of T‐DNA tags in coding and intergenic regions showed a good correlation with the predicted size distribution of these sequences in the genome. However, the frequency of T‐DNA insertions in 3′‐ and 5′‐regulatory regions of genes, corresponding to 300 bp intervals 3′ downstream of stop and 5′ upstream of ATG codons, was 1.7–2.3‐fold higher than in any similar interval elsewhere in the genome. The additive frequency of insertions in 5′‐regulatory regions and coding domains provided an estimate for the mutation rate, suggesting that 47.8% of mapped T‐DNA tags induced knockout mutations in Arabidopsis.

Szabados, L., Kovács, I., Oberschall, A., Ábrahám, E., Kerekes, I., Zsigmond, L., Nagy, R., Alvarado, M., Krasovskaja, I., Gál, M., Berente, A., Rédei, G. P., Haim, A. B., & Koncz, C. (2002). Distribution of 1000 sequenced T‐DNA tags in the Arabidopsis genome. The Plant Journal, 32(2), 233–242. Portico.