Development of barley aleurone cells: temporal and spatial patterns of accumulation of cell-specific mRNAs

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Abstract
The mechanisms underlying the response of the mature barley (Hordeum vulgare L.) aleurone layer to gibberellic acid have received much attention, but little is known about the developmental basis for this response. We have investigated the spatial and temporal accumulation of mRNAs complementary to two barleygrain cDNAs that are differentially expressed in the aleurone layer of the developing endosperm. Messenger RNA complementary to one of these clones (B11E; Jakobsen etal., 1989, Plant Mol. Biol. 12, 285–293) accumulates exclusively in the aleurone layer of developing grains where it is uniformly distributed in all three cell layers. Accumulation of B11E mRNA is first detectable 10 d post an thesis (DPA), increases 200-fold up to 25 DPA, and then declines towards grain maturity. Messenger RNA complementary to the other clone, B22E, shows a more complex pattern of expression. In addition to the aleurone layer, this mRNA accumulates in the vascular tissue of the maternal pericarp and embryo axis, as well as in the parenchyma cells of the embryonic scutellum. In excised immature embryos abscisic acid strongly suppresses accumulation of B22E mRNA. The B22E transcript is absent from mature embryos, but rapidly reappears after germination.