Figure 1.

sRNAs correspond to the 5'-ends of chloroplast mRNAs in Chlamydomonas. (A) The sequences corresponding to four chloroplast sRNAs (Supplementary Table S1) are highlighted in bold. The position of the 5'-ends as mapped by RACE is shown with arrowheads. The numbers above the arrowheads indicate the number of 5'-RACE clones that end at the respective sites. Most clone ends coincide with sRNA 5'-ends. (B) Sequence alignment of the psbB 5' and psbH 5' sRNAs. Asterisks indicate conserved positions. (C) Autoradiograms of an RNA blot of chloroplast RNA from the WT and the mbb1 mutant hybridized with the radioactive probes indicated above the panels. The arrows indicate the positions of the sRNAs. Low molecular weight RNA was enriched from total RNA and separated on a 15% sodium dodecyl sulphate-polyacrylamide gel electrophoresis containing 8 M urea. A fluorescence image of the gel lanes stained with ethidium bromide is shown as loading control in the leftmost panel. The probes were single-stranded DNA oligonucleotides (≤25 nt) antisense to the sRNAs. The same membrane was repeatedly probed and stripped as described in Materials and Methods section.