Abstract
Gene modification by gene targeting (GT) via homologous recombination is a powerful tool not only for the analysis of the function of the gene of interest but also for the molecular breeding of crops. GT is thought to be clean transformation technology because it can modify the only targeted gene predictably, although transgenes are integrated at random loci in conventional transformation system. In this study, we succeeded in the modification of endogenous rice OASA2 gene, that encodes anthranilate synthase, a key enzyme in tryptophan (Trp) biosynthesis, by T-DNA mediated GT. Southern blot analysis in T0 and T1 generation showed that true GT, in which wild-type OASA2 gene was modified as expected, was occurred in this plant. Moreover, the content of free Trp in the leaf of GT plant homozygous of modified OASA2 gene was much higher than that in wild-type.
