Expression classes and numbers of tissue of annotated and non annotated sequences. A-C: Number of annotated and nonannotated sequences per expression class for xylem from juvenile trees (A), roots (B) and young foliage (C). Other tissues are shown in Additional file 8: Figure S5. D: Number of tissues in which each annotated and non-annotated sequence was detected. Frequency, number of genes in a given intensity class or detected in a given number of tissues types.