Table II.

Expression of GUS reporter gene in reciprocal crosses

Recipient PistilPollen DonorExpression in Early EmbryoLate Expression in Mature Seeds
GUS+GUSGUS+cotyledonsGUS cotyledons
pSP2-1Co-gl 3528631
Co-gl pSP2-106369133
pSP2-8Co-gl 67167369
Co-gl pSP2-80782828

The SIN1/SUS1/CAF putative promoter GUS fusion pSP2 is transcriptionally active post-fertilization only if contributed from the maternal gamete. This silencing of the paternal allele is released by the time pSP2 activity reappears, at the late walking stick stage of embryogenesis. The pollinated pistils were dissected either 3 d postpollination, at a pistil length of 2.5 to 3.0 mm, to score for GUS activity in early embryogenesis, or 10 d postpollination to score for activity in late embryogenesis. The GUS fusion lines are labeled pSP2-1 and pSP2-8, whereas the wild-type control is Co-gl.