FIGURE 7.

RNA-editing levels at the MEF8 and MEF8S target sites in pollen and in leaves of the respective knock-out mutants correspond with the expression levels of the remaining MEF8S and MEF8 genes. A, Atgenexpress data (48) show that MEF8S expression levels (measured as quantities of steady-state RNA signals) increase in stamen tissues and in pollen, whereas transcript levels of MEF8 are lower in these cells than in any other plant tissue. B, pollen kernels were collected from still closed flower buds, and the cDNA obtained from the young pollen was analyzed for editing at the two target sites. Pollen from the homozygous mutant plant mef8-2 with intact MEF8S alleles (center sequencing panels; gray bars in histograms on the right) is hardly affected, and editing levels are similar to those in pollen from wild type Col plants (left sequencing panel). In leaves, editing at both target sites is reduced (black bars in histograms on the right; Figs. 1 and 2). Editing in pollen from the homozygous mutant plant mef8s-1 (right sequencing panels; gray bars in histograms on the right) is severely reduced whereas editing in leaves is unaffected. In pollen, the intact MEF8 alleles cannot compensate the loss of MEF8S, possibly because of the low expression of MEF8 in these tissues.