Alonso et al. used selected Agrobacterium transferred DNA (T-DNA) to generate about 150,000 transformed A. thaliana plants. The genomic location of each integration event was mapped - identifying 88,122 T-DNA/genome junction sequences, and confirming the generation of mutation in 21,799 of the 29,454 annotated genes. The preferences and frequencies of T-DNA integration on an individual chromosome level, within specific genetic elements (e.g., UTRs), and on a gene expression basis were all investigated.The authors then screened their collection for genes responsive to treatment with ethylene - a plant hormone involved in disease resistance and fruit ripening. Using this approach, they were able to isolate mutant plants for a new family of ethylene response DNA binding factors."One of the most significant findings revealed through analysis of genomes of multicellular organisms is the large number of genes for which no function is known or can be predicted. An essential tool for the functional analysis of these completely sequenced genomes is the ability to create loss-of-function mutations for all of the genes," conclude the authors.