Abstract
Arabidopsis leafy cotyledon type mutants such as lec1 impaired with seed maturation are characterized as heterochronic mutants because they exhibit traits of post-germinative development such as trichome formation in cotyledons during embryogenesis. To explore the molecular basis of their heterochronic characters, we identified many genes that heterochronically express during embryogenesis by microarray analysis. Among them, PYK10, encoding an ER-body localized β-glucosidase, which is normally not expressed during embryogenesis, was found to be strongly expressed in the lec1 embryo. Stochastic expression of PYK10 promoter:GFP was observed in single or neighboring multiple cells at the early heart stage of the mutant embryo, and the number of GFP expressing cells increased along the cell files as the embryo developed. Such patterns are reminiscent of release from epigenetic repression and suggest that LEC1 functions to maintain such a repressed status. In addition, we isolated several novel mutants, in which PYK10:GFP was heterochronically expressed during embryogenesis. We will be discussed in relation to temporal regulation of gene repression during embryogenesis.
