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Protoplasma

, Volume 248, Issue 2, pp 425–435 | Cite as

Syncytia in plants: cell fusion in endosperm—placental syncytium formation in Utricularia (Lentibulariaceae)

  • Bartosz J. Płachno
  • Piotr Świątek
New Ideas in Cell Biology

Abstract

The syncytium formed by Utricularia is extremely unusual and perhaps unique among angiosperm syncytia. All typical plant syncytia (articulated laticifers, amoeboid tapetum, the nucellar plasmodium of river weeds) are formed only by fusion of sporophytic cells which possess the same genetic material, unlike Utricularia in which the syncytium possesses nuclei from two different sources: cells of maternal sporophytic nutritive tissue and endosperm haustorium (both maternal and paternal genetic material). How is this kind of syncytium formed and organized and is it similar to other plant syncytial structures? We used light and electron microscopy to reconstruct the step-by-step development of the Utricularia syncytia. The syncytia of Utricularia developed through heterotypic cell fusion involving the digestion of the cell wall, and finally, heterokaryotic multinucleate structures were formed, which possessed different-sized nuclei that were not regularly arranged in the cytoplasm. We showed that these syncytia were characterized by hypertrophy of nuclei, abundant endoplasmic reticulum and organelles, and the occurrence of wall ingrowths. All these characters testify to high activity and may confirm the nutritive and transport functions of the syncytium for the developing embryo. In Utricularia, the formation of the syncytium provides an economical way to redistribute cell components and release nutrients from the digested cell walls, which can now be used for the embryo, and finally to create a large surface for the exchange of nutrients between the placenta and endosperm.

Keywords

Embryology Cell fusion Endosperm haustoria Syncytium Embryo nutrition 

Notes

Acknowledgments

This study was funded by grant N N304 002536 from the Polish Ministry of Science and Higher Education. The first author gratefully acknowledges the support of an award from the Foundation for Polish Sciences (Start Programme). We thank our colleague Dr. Lubomir Adamec for kindly providing part of the material for this study and for hosting BJP in Třeboň. We particularly thank the reviewers for their very helpful suggestions for making our manuscript clearer.

Conflict of interest

None

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Plant Cytology and EmbryologyJagiellonian UniversityCracowPoland
  2. 2.Department of Animal Histology and EmbryologyUniversity of SilesiaKatowicePoland

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