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14-3-3 isoforms and pattern formation during barley microspore embryogenesis

Maraschin, S. de F., Lamers, G.E.M., Pater, B.S. de., Spaink, H.P., Wang, M.
Journal of experimental botany 2003 v.54 no.384 pp. 1033-1043
apical meristems, plant development, protein synthesis, Hordeum vulgare, androgenesis, isomers, gene expression, multigene family, cell differentiation, plant proteins
The members of the 14-3-3 isoform family have been shown to be developmentally regulated during animal embryogenesis, where they take part in cell differentiation processes. 14-3-3 isoform-specific expression patterns were studied in plant embryogenic processes, using barley (Hordeum vulgare L.) microspore embryogenesis as a model system. After embryogenesis induction by stress, microspores with enlarged morphology showed higher viability than non-enlarged ones. Following microspore culture, cell division was only observed among the enlarged microspores. Western blot and immunolocalization of three barley 14-3-3 isoforms, 14-3-3A, 14-3-3B and 14-3-3C were carried out using isoform-specific antibodies. The level of 14-3-3C protein was higher in enlarged microspores than in non-enlarged ones. A processed form of 14-3-3A was associated with the death pathway of the non-enlarged microspores. In the early embryogenesis stage, 14-3-3 subcellular localization differed among dividing and non-dividing microspores and the microspore-derived multicellular structures showed a polarized expression pattern of 14-3-3C and a higher 14-3-3A signal in epidermis primordia. In the late embryogenesis stage, 14-3-3C was specifically expressed underneath the L1 layer of the shoot apical meristem and in the scutellum of embryo-like structures (ELSs). 14-3-3C was also expressed in the scutellum and underneath the L1 layer of the shoot apical meristem of 21 d after pollination (DAP) zygotic embryos. These results reveal that 14-3-3A processing and 14-3-3C isoform tissue-specific expression are closely related to cell fate and initiation of specific cell type differentiation, providing a new insight into the study of 14-3-3 proteins in plant embryogenesis.