Endogenous Nod-factor-like signal molecules promote early somatic embryo development in Norway spruce.
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.
Dyachok
Julia V
JV
Department of Chemistry, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.
Wiweger
Malgorzata
M
Kenne
Lennart
L
von Arnold
Sara
S
D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D002688:Chitinases / Q000378:metabolism; D006540:Herbicides / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000378:metabolism*; D028222:Picea / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction
D006540:Herbicides; D008070:Lipopolysaccharides; C092736:Nod factor, Rhizobium leguminosarum; C023023:lipid-linked oligosaccharides; D015084:2,4-Dichlorophenoxyacetic Acid; D002688:Chitinases