The accumulation of plastid ribosomes is reduced in mterf6 mutants. A, Total RNA preparations of MS medium-grown wild-type (Col-0), mterf6-1, mterf6-2, rnr1-3, prps17-1, and prpl24-1 seedlings were run on a Bioanalyzer (Supplemental Fig. S2C), and changes in rRNA ratios were calculated with ImageJ (Col-0 set to 1). Error bars indicate sd. 23SHB2, HIDDEN BREAK2 product of 23S rRNA. B, Immunoblot analysis of representative plastid ribosome subunits. Total leaf protein extracts from wild-type (Col-0), mterf6-1, mterf6-2, and rnr1-3 seedlings were fractionated by SDS-PAGE, and blots were probed with antibodies raised against the plastid-encoded Rps7 and the nucleus-encoded RPS5 and RPL4 proteins. Increasing levels of wild-type proteins were loaded in the lanes marked 0.25× Col-0, 0.5× Col-0, and Col-0. Loading was adjusted to the fresh weights of seedlings. The Ponceau Red (Ponc.)-stained blot served as the loading control. Quantification of signals relative to the wild type (=1) is provided below each mutant lane.