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Signal molecules in embryogenesis of Norway spruce

Wiweger, Malgorzata (2003). Signal molecules in embryogenesis of Norway spruce. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 293
ISBN 91-576-6527-3
[Doctoral thesis]

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Signaling molecules regulating embryo development have been described in angiosperms, but very little is known about how embryogenesis is controlled in gymnosperms. In this work we show that lipophilic low molecular weight molecule(s) with GlcNAc residues that are sensitive to chitinase are secreted by embryogenic cultures of Norway spruce. These data indicate that lipo-chitooligosaccharides (LCOs), homologous with rhizobial Nod factors, are present in plants. Interestingly, developmentally blocked lines secrete more LCOs than normally developing lines do. Endogenous LCOs from spruce and rhizobial Nod factors suppress programmed cell death (PCD) and stimulate proliferation of proembryogenic masses and somatic embryo formation but not further embryo development. LCOs are known to be degraded by chitinases. The Chia4-Pa1 gene, encoding for class IV chitinase, was isolated and characterised. The Chia4-Pa1 gene belongs to a small family with highly similar members. The expression of Chia4-Pa genes increases significantly after withdrawal of plant growth regulators, i.e. during a treatment that triggers PCD and stimulates the switch from proliferation of proembryogenic masses to somatic embryo differentiation. Based on the spatial expression pattern of Chia4-Pa, I propose that chitinase-expressing cells have a megagametophyte signaling function. The localisation of the CHIA4-Pa proteins does not correspond to the expression pattern of the encoding genes. I suggest that the CHIA4-Pa proteins are targeted to places where the substrates are localised. Furthermore, chitinases might act on arabinogalactan proteins (AGPs) thereby causing cell wall loosening and cell elongation. In our laboratory, work is being carried out to identify markers specific for different developmental stages of embryo development in Norway spruce. The level of endogenous LCOs secreted to a medium might be used as an indicator of the embrogenic potential of the proliferating cultures, while the increased level of Chia4-Pa transcript coincides with massive PCD and differentiation of somatic embryos. In addition, the PaHB2 gene, a member of the sub-group of the HD-GL2 family with subepiderm- and protoderm/epiderm-specificity, was isolated and characterised.

Authors/Creators:Wiweger, Malgorzata
Title:Signal molecules in embryogenesis of Norway spruce
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :November 2003
Number of Pages:53
ALLI. Dyachok J., Wiweger M., Kenne L. and von Arnold S. (2002). Endogenous Nod-Factor-Like Signal Molecules Suppress Cell Death and Promote Early Somatic Embryo Development in Norway spruce. Plant Physiology 128: 523-533. II. Wiweger M., Dyachok J., Gohil S., Kenne L. and von Arnold S. The impact of endogenous lipophilic chitooligosaccharides on embryo development in Norway spruce. (manuscript). III. Wiweger M., Farbos I., Ingouff M., Lagerctantz U. and von Arnold S. (2003). Expression of Chia4-Pa chitinase genes during somatic and zygotic embryo development in Norway spruce (Picea abies): similarities and differences between gymnosperm and angiosperm class IV chitinases. J. Exp. Bot. 54: 2691-2699. IV. Ingouff M., Farbos I., Wiweger M and von Arnold S. (2003). The molecular characterization of PaHB2, a homeobox gene of the HD-GL2 family expressed during embryo development in Norway spruce. J. Exp. Bot. 54: 1343-1350.
Place of Publication:Uppsala
ISBN for printed version:91-576-6527-3
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F62 Plant physiology - Growth and development
F Plant production > F30 Plant genetics and breeding
Subjects:Not in use, please see Agris categories
Agrovoc terms:chitinase, homeoboxes, genetic markers, picea abies, somatic embryogenesis, apoptosis, plant embryos
Keywords:AGP, chitinase, homeobox, LCO, markers, Picea abies, signaling molecule, somatic embryogenesis
Permanent URL:
ID Code:409
Department:(NL, NJ) > Dept. of Plant Biology and Forest Genetics (until 131231)
Deposited By: Malgorzata Wiweger
Deposited On:01 Dec 2003 00:00
Metadata Last Modified:02 Dec 2014 10:04

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