IMPORTANCE OF ARABINOGALACTAN PROTEINS FOR THE DEVELOPMENT OF SOMATICEMBRYOS OF NORWAY SPRUCE (PICEA-ABIES)

The morphology of somatic embryos of Norway spruce (Picea abies) varie s among different cell lines, from less developed somatic embryos with small embryonic regions (group B) to well developed embryos with larg e embryonic regions (group A). Only well developed somatic embryos wil l undergo a maturation process after a treatment with ABA and develop into mature somatic embryos, which is required for plant regeneration. We have previously shown that the presence of specific extracellular proteins can be correlated with the morpohology of the somatic embryos , In the present study we show that extracellular proteins concentrate d from group A cell lines can stimulate group B embryos to develop fur ther and that seed extract can stably convert B embryos into A embryos . The arabinogalactan protein (AGP) fraction of the extracellular prot eins and of the seed extract was shown to be an active component for s timulating B embryos to develop further. Furthermore, the amount and t ype of extracellular AGPs, as detected with beta-glucosyl Yariv reagen t and monoclonal antibodies, varied among different types of tissues a nd cell lines. The data show that development of somatic embryos in No rway spruce is associated with particular extracellular AGPs, which ha ve a regulatory function.