Hourglass cell development in the soybean seed coat

Abstract

Hourglass cells (HGCs) are one of three main cell types in the soybean seed coat. We have studied their structure during the early phases of seed coat development, from 9 to 45 days post anthesis (dpa), by four different microscopic techniques. At 9dpa HGCs resemble typical plant cells but from 12-18dpa they under go rapid changes in their internal and external structure. By 18dpa they have assumed the typical hourglass shape with thick cell walls composed of layers of pectic material, intercellular air spaces and large central vacuoles. By 45dpa, all organelles in HGCs have been degraded. Additional experiments have shown that plasmodesmata connect all cell types and that soybean peroxidase is localized to the HGC. These results increase our understanding of the structure and development of the HGC and will be valuable for future studies on protein targeting to components of the endomembrane systems within them.