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Programmed cell death and genetic stability in conifer embryogenesis

Helmersson, Andreas (2007). Programmed cell death and genetic stability in conifer embryogenesis. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2007:127
ISBN 978-91-85913-26-8
[Doctoral thesis]

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Somatic embryogenesis, the generation of embryos from somatic cells, is a valuable tool for studying embryology. In addition, somatic embryos can be used for large-scale vegetative propagation, an application of great interest for forestry. A critical event during early embryo differentiation in conifers is the apical basal polarization, which proceeds through the establishment of two embryonic parts: the proliferating embryonal mass and the terminally differentiated suspensor. The development of both parts is strictly coordinated and imbalance causes embryonic defects. The suspensor cells are eliminated by programmed cell death (PCD). In animals, caspase family proteases are the main executioners of PCD. In this work we have used synthetic peptide substrates containing caspase recognition sites and corresponding specific inhibitors to analyse the role of caspase-like activity during early embryo differentiation in Norway spruce (Picea abies L. Karst.). We found that VEIDase is the principal caspase-like activity. This activity is localized specifically in suspensor cells, and its inhibition prevents normal embryo development by blocking the suspensor differentiation. The in vitro VEIDase activity was shown to be highly sensitive to pH, ionic strength, temperature and zinc concentration. In vivo studies with Zinquin, a zinc-specific fluorescent probe, revealed a high accumulation of intracellular free zinc in the embryonal masses and an abrupt decrease in the suspensor. Increased zinc concentration in the culture medium suppresses terminal differentiation and PCD of the suspensor. In accordance, exposure of early embryos to TPEN, a zinc-specific chelator, induces ectopic cell death affecting embryonal masses. This establishes zinc as an important factor affecting cell fate specification during plant embryogenesis. Before somatic embryos can be accepted for clonal propagation it is important to show that the regenerated plants have similar growth to that of seedlings and are genetically uniform. The genetic integrity during zygotic and somatic embryogenesis in Norway spruce and Scots pine (Pinus sylvestris L.) was investigated by comparing the stability of variable nuclear microsatellite loci. The stability varied significantly among families in both species during somatic embryogenesis. Scots pine families showing low genetic stability during establishment of embryogenic cultures had a higher embryogenic potential than those that were genetically more stable. In contrast, embryo development was suppressed in genetically unstable families. The stability of microsatellites was in general higher in zygotic embryos than in somatic embryos. No deviation in growth was observed in somatic embryo plants of Norway spruce carrying mutated microsatellites.

Authors/Creators:Helmersson, Andreas
Title:Programmed cell death and genetic stability in conifer embryogenesis
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2007
Number of Pages:48
ALLI. Helmersson, A., von Arnold, S., Burg, K., Bozhkov, P.V. 2004. High stability of nuclear microsatellite loci during the early stages of somatic embryogenesis in Norway spruce. Tree Physiology 24(10), 1181-6. II. Bozhkov PV, LH Filonova, MF Suarez, A Helmersson, AP Smertenko, B Zhivotovsky, von Arnold S. 2004. VEIDase is a principal caspase-like activity involved in plant-programmed cell death and essential for embryonic pattern formation. Cell Death and Differentiation 11(2), 175-82. III. Helmersson, A., von Arnold, S., Bozhkov, P.V. The level of free intracellular zinc controls programmed cell death/cell survival decisions in plant embryos. (Manuscript). IV. Burg, K., Helmersson, A., Bozhkov, P., von Arnold, S. 2007. Developmental and genetic variation in nuclear microsatellite stability during somatic embryogenesis in pine. Journal of Experimental Botany 58(3), 687-98. V. Helmersson, A., Jansson, G., Bozhkov, P.V., von Arnold, S. Genetic variation in microsatellite stability of somatic embryo plants of Picea abies: a case study using six unrelated full sib families. (Provisionally accepted for publication in Scandinavian Journal of Forestry).
Place of Publication:Uppsala
ISBN for printed version:978-91-85913-26-8
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:picea abies, pinus sylvestris, gymnosperms, apoptosis, somatic embryogenesis, somatic embryos, microsatellites, genetic markers, genetic stability, genetic variation, zinc
Keywords:developmental PCD, gymnosperms, simple sequence repeat microsatellite marker, somatic embryogenesis, VEIDase, Zinc, Zinquin-etyl-ester
Permanent URL:
ID Code:1637
Department:(NL, NJ) > Dept. of Plant Biology and Forest Genetics (until 131231)
Deposited By: Andreas Helmersson
Deposited On:21 Nov 2007 00:00
Metadata Last Modified:02 Dec 2014 10:13

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