Fertilization induces strong accumulation of a histone deacetylase (HD2) and of other chromatin-remodeling proteins in restricted areas of the ovules.

Abstract

Fertilization triggers a unique and complex developmental program leading to embryogenesis and seed set. Recently, mutations affecting chromatin-remodeling enzymes in plants have shown their key roles in development as demonstrated before in animal cells. Using a negative selection screen to isolate genes expressed in ovary tissues upon fertilization, we have identified a histone deacetylase gene (named ScHD2a ) of the plant-specific HD2 family, which is predominantly expressed in ovaries of the self-incompatible species Solanum chacoense. The ScHD2a is the probable orthologue of the Arabidopsis thaliana AtHD2a gene, which upon antisense suppression leads to aborted seeds formation. Transcription of the ScHD2a gene is strongly triggered by fertilization and transcripts accumulate predominantly in the micropylar region of the ovule's integument. Interestingly, this fertilization-induced accumulation pattern was also observed for other genes involved in transcriptional repression but not for a MYST-family histone acetyltransferase. The strong increase in ScHD2a mRNA levels in ovules after fertilization suggests an important and localized role for transcriptional repression in seed development, and indicates why silencing of the AtHD2a gene leads to aborted seed formation.