Title: ``A microarray-based screen for targets of a chromatin remodeling factor in Arabidopsis''
Speakers: Dr. Joe Ogas (Department of Biochemistry) and Dr. Jeanne Romero-Severson (Departments of Agronomy and Forestry)
Place: LILLY G126; Tuesday, 4:30pm

In angiosperms, germination represents an important developmental transition during which embryonic identity is repressed and vegetative identity emerges. PICKLE (PKL) encodes a CHD3-chromatin remodeling factor necessary for the repression of expression of LEAFY COTYLEDON1 (LEC1), a central regulator of embryogenesis. A candidate gene approach and microarray analysis identified nine additional genes that exhibit robust PKL-dependent repression of expression during germination. Transcripts for all three LEAFY COTYLEDON genes, LEC1, LEC2, and FUS3, exhibit PKL-dependent repression, and all three transcripts are elevated more than 100-fold in pkl primary roots that inappropriately express embryonic traits ("pickle roots"). Three other genes that exhibit PKL-dependent regulation have expression patterns correlated with zygotic or somatic embryogenesis, and one gene encodes a putative LIM domain transcriptional regulator that is preferentially expressed in siliques. Genes that exhibit PKL-dependent repression during germination are not necessarily regulated by PKL at other points in development. Our data suggest that PKL selectively regulates a suite of genes during germination to repress embryonic identity. In particular, we propose that PKL acts as a master regulator of the LEAFY COTYLEDON genes, and joint derepression of these genes is likely to contribute substantially to expression of embryonic identity in pkl seedlings.