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New Phytol. 2016 Oct;212(1):232-43. doi: 10.1111/nph.14012. Epub 2016 May 27.

EXTRA SPINDLE POLES (Separase) controls anisotropic cell expansion in Norway spruce (Picea abies) embryos independently of its role in anaphase progression.

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Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO Box 7080, SE-75007, Uppsala, Sweden.
Department of Chemistry and Biotechnology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO Box 7015, SE-75007, Uppsala, Sweden.
Departamento de Biologia Molecular y Bioquimica, Facultad de Ciencias, Universidad de Malaga, 290071, Malaga, Spain.
The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK.
Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA.
Institute for Global Food Security, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, UK.


The caspase-related protease separase (EXTRA SPINDLE POLES, ESP) plays a major role in chromatid disjunction and cell expansion in Arabidopsis thaliana. Whether the expansion phenotypes are linked to defects in cell division in Arabidopsis ESP mutants remains elusive. Here we present the identification, cloning and characterization of the gymnosperm Norway spruce (Picea abies, Pa) ESP. We used the P. abies somatic embryo system and a combination of reverse genetics and microscopy to explore the roles of Pa ESP during embryogenesis. Pa ESP was expressed in the proliferating embryonal mass, while it was absent in the suspensor cells. Pa ESP associated with kinetochore microtubules in metaphase and then with anaphase spindle midzone. During cytokinesis, it localized on the phragmoplast microtubules and on the cell plate. Pa ESP deficiency perturbed anisotropic expansion and reduced mitotic divisions in cotyledonary embryos. Furthermore, whilst Pa ESP can rescue the chromatid nondisjunction phenotype of Arabidopsis ESP mutants, it cannot rescue anisotropic cell expansion. Our data demonstrate that the roles of ESP in daughter chromatid separation and cell expansion are conserved between gymnosperms and angiosperms. However, the mechanisms of ESP-mediated regulation of cell expansion seem to be lineage-specific.


cell cycle; embryogenesis; microtubules; proteases; separase; spruce (Picea abies)

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