Plant Physiol, February 2002, Vol. 128, pp. 523-533
Endogenous Nod-Factor-Like Signal Molecules Promote Early Somatic
Embryo Development in Norway Spruce1
Julia V.
Dyachok,2
Malgorzata
Wiweger,3
Lennart
Kenne, and
Sara
von Arnold*
Department of Forest Genetics (J.V.D., M.W., S.v.A) and Department
of Chemistry (L.K.), Swedish University of Agricultural Sciences,
S-750 07 Uppsala, Sweden
Embryogenic cultures of Norway spruce (Picea
abies) are composed of pro-embryogenic masses (PEMs) and
somatic embryos of various developmental stages. Auxin is important for
PEM formation and proliferation. In this report we show that depletion
of auxin blocks PEM development and causes large-scale cell death.
Extracts of the media conditioned by embryogenic cultures stimulate
development of PEM aggregates in auxin-deficient cultures. Partial
characterization of the conditioning factor shows that it is a
lipophilic, low-molecular-weight molecule, which is sensitive to
chitinase and contains GlcNAc residues. On the basis of this
information, we propose that the factor is a lipophilic chitin
oligosaccharide (LCO). The amount of LCO correlates to the
developmental stages of PEMs and embryos, with the highest level in the
media conditioned by developmentally blocked cultures. LCO is not
present in nonembryogenic cultures. Cell death, induced by withdrawal
of auxin, is suppressed by extra supply of endogenous LCO or Nod factor
from Rhizobium sp. NGR234. The effect can be mimicked by
a chitotetraose or chitinase from Streptomyces griseus.
Taken together, our data suggest that endogenous LCO acts as a signal
molecule stimulating PEM and early embryo development in Norway spruce.
1
This work was supported by the Royal Swedish
Academy of Forestry and Agriculture (to J.V.D.) and by the Swedish
International Development Cooperation Agency (to M.W.).
2
Present address: Institute of Cell Biology and Genetic
Engineering, 148 Zabolotnogo St., 252143 Kiev, Ukraine.
3
Present address: Plant Breeding and Acclimatization
Institute, Radzikow, 05-870 Blonie, Poland.
*
Corresponding author; e-mail Sara.von.Arnold{at}sgen.slu.se; fax
46-18-67-32-79.
© 2002 American Society of Plant Physiologists
