M. Sauter et al., CELL-CYCLE REGULATORY GENES FROM MAIZE ARE DIFFERENTIALLY CONTROLLED DURING FERTILIZATION AND FIRST EMBRYONIC-CELL DIVISION, Sexual plant reproduction, 11(1), 1998, pp. 41-48
Regulation of early embryo development in higher plants is not underst
ood. As one approach to gain insight into the mechanisms that govern z
ygotic embryogenesis, we studied the regulation of zygotic cell divisi
on by analyzing expression of cell cycle regulatory genes. Transcripts
of cdc2 and cyclin genes as well as of a histone gene from maize were
detected in single cells by employing recently developed techniques w
hich allow fertilization of isolated gametes and zygote culture in vit
ro. We analyzed gene expression in sperm cells, in the egg cell and in
other cells present in the embryo sac, i.e. synergids, central cell a
nd antipodal cells. Moreover, in vitro gamete fusion enabled us to exa
mine gene expression in the zygote at defined time points from fertili
zation to the two-celled embryo stage. Whereas the cdc2 gene is expres
sed constitutively in all cells of the embryo sac, in sperm cells, and
throughout zygote development, the cyclin genes display cell-specific
expression in the embryo sac and differential expression during zygot
e development. All three cyclins examined are transcribed de novo afte
r fertilization, indicating a different level of embryonic cell cycle
regulation in plants than what is commonly found in animals where earl
y embryonic cell divisions are driven by maternally supplied cyclin mR
NA.