A novel Ti‐plasmid‐convertible λ phage vector system suitable for gene isolation by genetic complementation of Arabidopsis thaliana mutants

A new λ phage vector system, λTI, has been constructed to facilitate genetic complementation of higher plant mutations. The λTI vectors are stable, and by using the Cre—lox site‐specific recombination, are automatically convertible into Ti‐plasmid binary vectors which are capable of expressing genes in higher plants. Two λTI vectors were constructed: (i) λTI1, which can generate a Ti‐plasmid that contains the cauliflower mosaic virus (CaMV) 35S promoter and is suitable for the expression of cDNA in transformed plants and (ii) λTI2, which can generate a Ti‐plasmid with the multicloning site (MCS). cDNA and genomic libraries, which were constructed from the cruciferous plant Arabidopsis thaliana in these λTI vectors, can be probed by large DNA fragments of more than 100 kb, such as yeast artificial chromosomes (YACs), enabling the direct screening of the clones in the chromosome region containing a specified genetic locus. These libraries will certainly become powerful tools for the genetic complementation of Arabidopsis mutant phenotypes by quickly providing transformation‐competent clones.