75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

167 Analysis of DNA methylation and expression of embryogenesis-related genes in plants
Tomiko Shibukawa, Akira Kikuchi, Hiroshi Kamada
University of Tsukuba, Japan
DNA methylation is known to involve in the regulation of gene expression. In animals, the hypomethylation of DNA
leads to the aberrant embryogenesis with abnormal expression of embryogenesis-related genes. On the other hand, in
plants, there is limited information about the relation between DNA methylation and embryogenesis.
In this study, we investigated the relation between DNA methylation and expression of embryogenesis-related genes
in plants (e.g. LEC1, ABI3 and FUS3 in Arabidopsis, C-LEC1 and C-ABI3 in carrot). The expression of embryogenesisrelated
genes was examined in various tissues (cotyledon, rosette leaf, root, apical tip, flower bud, flower and somatic
embryo) of Arabidopsis mutants deficient in DNA-methylation-related genes (e.g. ddm1 and cmt3). Some genes showed
different expression profiles in the mutants as compared to the wild type. In carrot, there are some induction systems of
somatic embryogenesis, which provide a large amount of synchronously developing embryos. Using the system, we tried
to clarify the relationship between the gene expression of embryogenesis-related genes (C-LEC1 and C-ABI3) and DNA
methylation on the genomic region during embryogenesis by Sourthen blot analysis, using isoschizomeric restriction
enzymes and bisulfite sequencing procedure. These results suggest that DNA methylation may involve in the regulation
of expression of embryogenesis-related genes.
168 Genetic Dissection of Parental Effects in Seed Development
Reza Shirzadi 1 , Moritz Nowack 2 , Reidunn Aalen 1 , Arp Schnittger 2 , Paul Grini 1
1
Department of Molecular Biosciences, University of Oslo, Norway, 2 2University Group at the Max-Planck-
Institute for Plant Breeding Research, Cologne, Germany
Seed development requires a coordinated interplay of the embryo, the endosperm and the maternal seed coat. The
embryo and the endosperm are the products of the double fertilization of the egg cell and the central cell by two sperm
cells from the pollen. What roles gametophytic parental (maternal and paternal) transcriptional programmes play in this
process is not clear. We have used the recently described cdc2a cell cycle mutant as a tool to dissect the involvement of
maternal and paternal gene programs in seed development. In the paternal effect cdc2a mutant line, mutant pollen fail
to undergo the second pollen mitosis, resulting in pollen with only one sperm cell instead of two. The single sperm cell
from cdc2a mutant pollen is able to successfully and exclusively fertilize the egg cell. cdc2a fertilized seeds eventually
arrest and abort, but although not fertilized, the central cell breaks the mitotic block and starts developing (autonomous)
endosperm. This identifies a novel positive signal from the fertilization of the egg cell that triggers endosperm development.
We have analyzed transcriptional profiles of cdc2a induced seed development and have identified several genes that that
show significant up- or down regulation compared to wild-type fertilization. The polycomb FIS-group of genes also
produce autonomous endosperm development when mutated, and are repressors of endosperm proliferation in the absence
of fertilization. One way of explaining seed abortion in cdc2a fertilization products is thus the repression of endosperm
development by active FIS-group genes. To test this hypothesis we fertilized FIS-group mutants with cdc2a pollen. In
the progeny of the crosses a up to three-fold higher frequency of cdc2a mutant plants could be found, showing that cdc2a
triggered diploid endosperm could support vital seed development in the absence of repression by the FIS-group genes.
This allows seed development without any paternal contribution to the endosperm and opens for an extensive exploration
of the transcriptional contribution of the paternal genome to endosperm development.