Abstract
Nucellar-derived cell cultures of sour orange (Citrus aurantium L.) proliferate as proembryogenic masses. By a change in the carbon source of the medium from sucrose to glycerol they are induced to undergo synchronous embryogenesis forming embryo initials that develop into globular embryos. The proembryogenic masses released glycoproteins to the medium. Exogenous addition of the glycoproteins to cells in glycerol-containing medium modified the course of embryo development in a dose-dependent manner. Addition of 20 μg · ml−1 of glycoproteins blocked embryogenesis and resulted in an accumulation of embryo initials. When glycoproteins were added to cultures containing advanced globularstage embryos further development was suppressed. The inhibitory component of the glycoproteins was found to be a family of polypeptides with apparent molecular masses of 53–57 kDa. While these proteins normally accumulated only in cultures of proembryogenic masses, they could be induced to accumulate in glycerol-containing medium by the addition of the glycoproteins. Thus, their accumulation was not a direct consequence of the type of growth medium used or the developmental state of the cultures. The results indicate that the 53-to 57 kDa glycoproteins could play a regulatory role in in-vitro embryogenesis in sour orange. The normal progression of embryo development appears to depend, in an obligatory manner, on the absence of these glycosylated extracellular proteins from the medium.
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Abbreviations
- kDa:
-
kilodalton
- PEM:
-
proembryogenic masses
- SDS-PAGE:
-
sodium dodecyl sulphate-polyacrylamide gel electrophoresis
- 2D-PAGE:
-
Two-dimensional polyacrylamide gel electrophoresis
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We thank Dr. S. Satoh (Institute of Biological Sciences, Tsukuba, Japan) for sending protein samples of the purified 57-kDa glycoprotein. This research was supported by a grant from the Charles H. Revson Foundation for Basic Research in the Life Sciences of the Israel Academy of Sciences. R.F. is a recipient of the Jack and Florence Goodman Career Development Chair.
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Gavish, H., Vardi, A. & Fluhr, R. Suppression of somatic embryogenesis in Citrus cell cultures by extracellular proteins. Planta 186, 511–517 (1992). https://doi.org/10.1007/BF00198030
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DOI: https://doi.org/10.1007/BF00198030