Abstract
Endosperm, which results from double fertilization event, has a unique transcriptional feature that is parental-origin-specific expression of imprinted genes. One of those imprinted genes in Arabidopsis is FWA whose transcription start site (TSS) is heavily methylated, and is transcriptionally silent in vegetative tissue. In endosperm tissue, the FWA expression occurs in association with decreasing of DNA methylation level at the TSS. However, the mechanism underlying the endosperm-specific expression remains unknown. To identify new components involved in this transcriptional regulation, we screened a mutagenized population of FWA promoter-GFP transgenic plants for mutants defective in GFP expression of endosperm. We have isolated the alac2 mutant, which causes the weak GFP expression in approximately half of the ovules. Moreover, a small percentage of ovules also showed abnormal GFP localization before feritilization and delayed nuclear division during early endosperm development. Map-based cloning revealed that the ALAC2 gene encodes a Fe-hydrogenase-like protein. A possible link between Fe-hydrogenase and the alac2 phenotype will be presented and discussed.
