Figure 8

BRAT promotes decay of maternally expressed mRNAs during the MZT via both the early and late decay machineries. K-means clustering analysis of the union of transcripts upregulated at any time point in brat mutant embryos partitioned transcripts into six classes on the basis of their expression in wild-type embryos. (A-F) Plots showing the average expression levels (RMA-normalized signal intensity) of the transcripts in each class, in wild-type (solid line) and brat mutant (dashed line) embryos, from 0 to 6 h post egg-laying. Below each plot are Venn diagrams depicting the overlap of the transcripts in each class with the set of BRAT-associated mRNAs defined by our RIP-Chip. These comparisons indicate that Classes A, B and C are significantly enriched for BRAT-associated mRNAs and therefore are likely to be direct targets of BRAT. In contrast, Classes D, E and F show no enrichment for BRAT-associated mRNAs, and are therefore likely upregulated as a result of secondary effects of the brat mutation. Given that Classes A, B, and C comprise maternally-expressed transcripts that undergo decay during the MZT, via the early (Classes A and B) and late (Class C) machineries (see text and Table 5), their stabilization in brat mutants indicates a role for BRAT in decay of maternal mRNAs during the MZT through both the early and late decay machineries. *P <10⁻⁶, **P <10⁻¹⁸ (Fisher’s exact test).