Abstract
Imprinted genes are expressed differently on the maternal and paternal chromosomes. In mammal, such differential gene expression is controlled by DNA methylation, which is erased and re-established in each generation. In contrast, molecular mechanism underling genomic imprinting in flowering plants had not been elucidated.
FWA, an Arabidopsis homeobox gene, displays maternal-origin-specific-expression in endosperm. The expression of FWA gene is always associated with hypomethylation of the tandem repeats around transcription starting site. We will report that the FWA imprinting is established by allele-specific activation rather than allele-specific silencing that is found in mammalian imprinting. Since endosperm is a terminally differentiated tissue, the activated FWA gene needs not to be reprogrammed again. We will also discuss how this simple controlling mechanism of FWA imprinting fits to the relatively complex sexual reproduction in flowering plants.
