Journal Article

Hourglass cell development in the soybean seed coat

S. S. Miller, Z. Jin, J. A. Schnell, M. C. Romero, D. C. W. Brown and D. A. Johnson

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 106, issue 2, pages 235-242
Published in print August 2010 | ISSN: 0305-7364
Published online May 2010 | e-ISSN: 1095-8290 | DOI:
Hourglass cell development in the soybean seed coat

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

Hourglass cells (HGCs) are prominent cells in the soybean seed coat, and have potential use as ‘phytofactories’ to produce specific proteins of interest. Previous studies have shown that HGCs initiate differentiation at about 9 d post-anthesis (dpa), assuming their characteristic morphology by 18 dpa. This study aims to document the structural changes in HGCs during this critical period, and to relate these changes to the concurrent development of a specific soybean peroxidase (SBP) encoded by the Ep gene.


Pods were collected from plants at specific growth stages. Fresh material was processed for analysis of Ep peroxidase activity. Tissues were processed for scanning and transmission electron microscopy, as well as extracted for western blotting. A null variety lacking expression of Ep peroxidase was grown as a control.

Key Results and Conclusions

At 9 dpa, HGCs are typical undifferentiated plant cells, but from 12–18 dpa they undergo rapid changes in their internal and external structure. By 18 dpa, they have assumed the characteristic hourglass shape with thick cell walls, intercellular air spaces and large central vacuoles. By 45 dpa, all organelles in HGCs have been degraded. Additional observations indicate that plasmodesmata connect all cell types. SBP activity and SBP protein are detectable in the HGC before they are fully differentiated (approx. 18 dpa). In very early stages, SBP activity appears localized in a vacuole as previously predicted. These results increase our understanding of the structure and development of the HGC and will be valuable for future studies aimed at protein targeting to components of the HGC endomembrane systems.

Keywords: Glycine max; soybean; seed coat; hourglass cells; development; peroxidase

Journal Article.  4488 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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