expression in developing and mature Scots pine seeds. (A) The relative expression of CAT 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. A star denotes significant (P <0.05) difference in the expression. (B) The localization of CAT mRNAs by in situ hybridization with DIG-labelled RNA-probes (blue signal) in a developing Scots pine seed at the early embryogeny. (C) The localization of CAT mRNAs at the late embryogeny. (D) Intense CAT expression in the developing embryos and in the megagametophyte at the early embryogeny. (E) Intense CAT expression in the nucellar layers at the early embryogeny. (F) Minor CAT expression in the nucellar layers at the late embryogeny. (G) Intense CAT expression in the cells of the leading embryo and minor CAT expression in the megagametophyte cells at the late embryogeny. cc = corrosion cavity, e = embryo, esr = embryo surrounding region, m = megagametophyte, nc = nucellar cap, nl = nucellar layers, nt = cellular nucellus, sr = suspensor remnants. Bars: 100 μm.