MiRNA expression patterns during silkworm embryonic development. (A) Hierarchical clustering analysis of the expression of 36 miRNAs obtained from embryos of early 1st instar larvae. The colors represent relative and mean-centered expression for each miRNA: green, low; black, mean; red, high. a and b represent the average signals of each probe printed at three points on each block. (B) Northern blotting analysis of miRNAs in the embryos and early 1st instar larvae. 5srRNA and U6 served as the loading controls.