expression in developing Scots pine seeds. (A) The relative expression of RBR in developing seeds at the early and late embryogeny and in the embryos (e) and megagametophytes (m) of mature seeds. The expression was based on mRNA copy numbers generated with the absolute Q-RT-PCR analysis and values presented were normalized using the expression at the early embryogeny. (B) The localization of RBR mRNAs (blue signal) in a developing Scots pine seed at the early embryogeny. (C) The localization of RBR mRNAs at the late embryogeny. (D) Minor RBR expression in the ESR of the megagametophyte at the early embryogeny. (E) Weak RBR expression in the cells of the nucellar layers at the early embryogeny. (F) Intense RBR expression in the cells of the nucellar layers at the late embryogeny. asr = arrow-shaped region, cc = corrosion cavity, e = embryo, esr = embryo surrounding region, m = megagametophyte, nc = nucellar cap, nl = nucellar layers, nt = cellular nucellus, sr = suspensor remnants. Bars: (D) 20 μm, (F) 50 μm, and (B, C, E) 100 μm.