Fig. 1. The AS event of  APXII  in Arabidopsis. a) Schematic representation of the AS pattern producing spinach chloroplastic APX mRNAs. Partial genomic DNA and mRNA sequences corresponding with the 3′-terminal regions of chloroplastic APXs (exons 11–13) are shown based on data from experiments reported previously ( Yoshimura  et al.  1999 ). Exon regions are shown as boxes and introns as lines. The open reading frame and untranslated regions are indicated by black and white boxes, respectively. Functional stop codons and polyadenylation signals for each mRNA variant are indicated by asterisks and poly(A), respectively. The position of the SRE sequence is indicated by a bold line. Arrows (S1–S5) indicate the location of primers used in this study ( Supplementary Table 1 ). b) Semiquantitative RT-PCR analysis to detect the chloroplastic APX mRNA variants (sAPX-I, -II, -III, and tAPX-I) in spinach and Arabidopsis. The 3′ region of the  APXII  gene (exons 11–13) with either WT or mutated SRE sequences from spinach driven by the CaMV 35S promoter was transformed into Arabidopsis using  A. tumefaciens . The sequences of WT and mutated SRE are shown. The line indicates the SRE region ( Yoshimura  et al.  2002 ). The terminal dinucleotides of acceptor site of intron 12 (ag) are indicated by boxes. Semiquantitative RT-PCR analysis (26 cycles) was carried out using sets of primers to detect the mRNA variants produced from the endogenous chloroplastic  APX  gene and the transgene in extracts from the leaves of 4-week-old spinach and 2-week-old transgenic Arabidopsis [Arabidopsis  APXII -1 (wild-type SRE) and Arabidopsis  APXII  (mutated SRE); T3 generation], respectively. Amplified products were electrophoresed on a 2% (w/v) agarose gel. M, molecular marker. The experiments were repeated at least 3 times using plants grown independently, and the representative results are shown.