Secretion of Specific Extracellular Proteins by Somatic Embryos of Picea abies is Dependent on Embryo Morphology
Ann. Bot. 1996, 77, 143-152, https://doi.org/10.1006/anbo.1996.0016
Mo HL, Egertsdotter U, von Arnold S

Abstract
Embryogenic cell lines ofPicea abieswere categorized into two groups, A and B, based on the morphology of the somatic embryos and the ability of the somatic embryos to proceed through a maturation process when treated with ABA. Group A embryos had a distinct, densely-packed embryonic region whereas group B embryos had loosely packed cells in their embryonic region. Embryo morphology was shown to be regulated by changes in the plant growth regulators in the culture medium. Treatment with N6-benzyladenine stimulated embryos to develop large embryonic regions. The morphology of somatic embryos and especially that of the embryonic regions was correlated with the presence of specific extracellular proteins. Only somatic embryos with densely packed cells in the embryonic regions secreted proteins with relative molecular weights of 28, 66 and 85kD. The extracellular protein of 28kD was isolated and the first 21 amino acids in the N-terminus were identified. These showed 52–57% identity with the N-terminal sequence conserved among members of a protein family which includes zeamatin and which have been shown to be involved in plant anti-fungal mechanisms. Immunological studies of extracellular chitinases and zeamatin-like proteins, as well as of activity of extracellular peroxidase, revealed a close correlation between the presence of specific chitinases and embryo morphology.

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