Characterization of the developmental stages of cypress zygotic embryos by two-dimensional electrophoresis and by cytochemistry

Biochemical changes that characterize megagametophyte and zygotic embryo development in the conifer Cupressus sempervirens L. (Cupressaceae) were studied by complementary methods of cytochemistry and two‐dimensional electrophoresis (2‐DE). These analyses revealed that early in their development megagametophytes and embryos were characterized by the predominant elaboration of starch in association with a low protein content. As their development proceeded, starch content gradually decreased while protein body synthesis progressively intensified, both in the megagametophyte and the embryo. In parallel, an increase in protein level as well as an accumulation of specific polypeptides could be observed in the two tissues. During maturation, protein bodies accumulated to high levels both in megagametophyte and embryo cells, whereas starch could no longer be detected. Protein levels were high in mature seeds and reached 12% and 8% of the megagametophyte and embryo DW, respectively. Some sets of polypeptides accumulated more specifically at this time in both megagametophyte and embryo. Some of these began to first accumulate in the megagametophyte during embryo development before their concentration rose in the embryo at cotyledonary stage. Others displayed a more specific‐embryo accumulation pattern.