Abstract

In the animal life cycle, the earliest manifestations of programmed cell death (PCD) can already be seen during embryogenesis, The aim of this work was to determine if PCD is also involved in the elimination of certain cells during plant embryogenesis, We used a model system of Norway spruce somatic embryogenesis, which represents a multistep developmental pathway with two broad phases. The first phase is represented by proliferating proembryogenic masses (PEMs), The second phase encompasses development of somatic embryos, which arise from PEMs and proceed through the same sequence of stages as described for their zygotic counterparts.Here we demonstrate two successive waves of PCD, which are implicated in the transition from PEMs to somatic embryos and in correct embryonic pattern formation, respectively, The first wave of PCD is responsible for the degradation of PEMs when they give rise to somatic embryos. We show that PCD in PEM cells and embryo formation are closely interlinked processes, both stimulated upon withdrawal or partial depletion of auxins and cytokinins. The second wave of PCD eliminates terminally differentiated embryo-suspensor cells during early embryogeny,During the dismantling phase of PCD, PEM and embryo-suspensor cells exhibit progressive autolysis, resulting in the formation of a large central vacuole, Autolytic degradation of the cytoplasm is accompanied by lobing and budding-like segmentation of the nucleus. Nuclear DNA undergoes fragmentation into both large fragments of about 50 kb and multiples of approximately 180 bp, The tonoplast rupture is delayed until lysis of the cytoplasm and organelles, including the nucleus, is almost complete, The protoplasm then disappears, leaving a cellular corpse represented by only the cell wall. This pathway of cell dismantling suggests overlapping of apoptotic and autophagic types of PCD during somatic embryogenesis in Norway spruce.

Keywords

plant embryogenesis; Norway spruce; programmed cell death; cell dismantling

Published in

Journal of Cell Science
2000, Volume: 113, number: 24, pages: 4399-4411

SLU Authors

• Stålhandske, Lada

  • Department of Forest Genetics, Swedish University of Agricultural Sciences
    

• Bozhkov, Peter

  • Department of Forest Genetics, Swedish University of Agricultural Sciences
    

• Daniel, Geoffrey

  • Department of Wood Science, Swedish University of Agricultural Sciences
    

• Von Arnold, Sara

  • Department of Forest Genetics, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Cell Biology
Forest Science


Permanent link to this page (URI)

https://res.slu.se/id/publ/109907