Fig. 7. PNPase activity and the extent of chloroplast mRNA polyadenyl ation are inversely correlated. (A) Scheme of the amplification and detection of polyadenylated mRNAs. (B) Southern blot analyses of RT–PCR products containing poly(A) sequences after 20 cycles of amplification. Equal amounts of RNA from wild-type (WT), PNPase over-expressing (+) and PNPase co-suppressed (–) plants were used for cDNA synthesis. A primer pair specifically amplifying the nuclear- encoded and constitutively expressed actin2 transcript was used as a control. C, RNA without reverse transcription.