Fig. 10. Expression of  APSI1  orthologs and AS efficiency of  APXII  in tissues of tobacco plants. Semiquantitative RT-PCR analysis detected NtAPSI1-1 and NtAPSI1-2 mRNAs, and the AS variants (sAPX-II, -III, and tAPX-I mRNAs) produced from the endogenous  APXII  gene in  N. tabacum  L. cv. SR1. Semiquantitative RT-PCR analysis (24–28 cycles) was carried out using sets of primers ( Supplementary Table 1 ) in extracts from the leaves, stems, and roots of 4-week-old plants. The positions of primers, except for T4, are similar to those of the spinach  APXII  gene in  Fig. 1a . The T4 primer was designed based on the middle region of exon 5. Amplified products were electrophoresed on a 2% (w/v) agarose gel. Equal loading of each amplified cDNA was determined using the control eIF1a PCR product. M, molecular marker. The experiments were repeated at least 3 times using plants grown independently, and the representative results are shown.