(A) A schematic diagram showing structural features of the inducible pX7-RNAi construct (see Guo et al. 2003 for detail), a chemical-inducible Cre/loxP (CLX) recombination system (Zuo and Chua 2000), to trigger the expression of an intron-containing inverted-repeat RNAi (IR). G10-90, a strong, synthetic, constitutive promoter._exo-Pdsi (exo-IR silencer): the reconstituted transcription unit derived from Cre/loxP-mediated DNA recombination after inducer treatment. endo-PDS (target): Genomic structure of the endogenous PDS gene. UTR, untranslated region of mRNA. Green boxes are exons of PDS separated by introns. Pds, fragment corresponding to the first 4 exons of PDS used for IR construction and probe for hybridization. (B) Phenotype of inducible PDSi at the post-germination stage. One-week-old seedlings were treated with inducer for one week and picture was taken at 10 days after removing inducer.