The Legume Non-Transgenic LORE1 Mutant Collection

Easy access to loss-of-function alleles of genes of interest greatly expedites hypothesis testing in plant science. The legume Lotus japonicus has been used successfully as a model system for identification of genetic components required for symbiotic nitrogen fixation using forward genetic approaches. To allow comprehensive reverse genetics investigation of symbiotic interactions as well as other traits of interest, we have developed the LORE1 insertion mutant resource. It takes advantage of the activity of the endogenous Gypsy-type retrotransposon LORE1, which transposes in the male germline, facilitating cost-efficient development of a large-scale non-transgenic mutant population. We have characterized a collection of ~100,000 mutagenized lines, identifying ~500,000 unique LORE1 insertions using a two-dimensional pooling scheme combined with next-generation sequencing. These lines provide exonic insertions in >85% percent of protein coding genes with coding sequence lengths larger than 1kb, with multiple alleles available for the majority of these. By conducting a forward-genetic screen for pale leaf phenotypes using the LORE1 collection, we found a tagging efficiency of at least 70%, indicating a relatively low level of background mutations. The LORE1 mutant lines, annotated with flanking sequence information and primers for genotyping, are available from: http://carb.au.dk/lore1/.