Transient expression of storage-protein genes during early embryogenesis of Vicia faba: synthesis and metabolization of vicilin and legumin in the embryo, suspensor and endosperm

Abstract

Abstract. Seed storage proteins are thought to be accumulated exclusively in the cell-expansion phase of embryogenesis and metabolized during germination and seedling growth. Here we show by a sensitive immunohistological technique that the two Vicia faba L. storage proteins vicilin and legumin are accumulated in substantial amounts in the suspensor and coenocytic endosperm and to a lesser extent in the mid-globular embryo. Both proteins appear and disappear at precise stages specific for each tissue. In the endosperm the accumulation starts around 12 d after pollination (DAP). After a maximum attained at 14-15 DAP, storage proteins are degraded within about 4 d. Accumulation is restricted to that part of the endosperm which covers the embryo and displays the highest levels of endoploidy (maximum 96n). In all other parts of the endosperm, storage proteins do not appear to accumulate, although storage-protein-specific mRNA synthesis takes place. In the suspensor, storage proteins are already observed at 6 DAP and disappear very quickly at approximately 10 DAP. Low amounts of legumin and vicilin are also detectable in the mid-globular embryo, but disappear completely as the embryo enters the heart stage. We conclude that storage proteins of Viciafaba accumulated transiently during early seed development are used as nutritive reserves for the growing embryo.

Tobacco embryogenesis: Storage-protein-accumulating cells of embryo, suspensor, and endosperm are able to undergo cytokinesis

“…Furthermore, a legumin B gene of V. faba transferred into tobacco showed the same biphasic expression behavior. Unexpectedly, in tobacco the early period of legumin accumulation coincides with a stage where the growth of embryo and endosperm is exclusively caused by a high rate of cell division and not by cell expansion (Panitz et al 1997). The massive storage protein deposition observed during the cell division phase of embryogenesis contradicts the widely accepted dogma that the mitotic cell does not conduct any storage protein deposition (Corke et al 1990a, Liu et al 1996.…”

An Aquaglyceroporin Is Abundantly Expressed Early in the Development of the Suspensor and the Embryo Proper of Loblolly Pine

“…The profile and localization of PtNIP1;1 expression is now being studied in greater detail to determine whether localization of expression varies over development, although present expression analyses (Fig. 4, A and B) would seem to preclude the type of suspensor-expression-early followed by embryo-properexpression-late pattern described by Panitz et al (1995).…”

“…Work by Panitz et al (1995) in broad bean (Vicia faba), showed transient accumulation of storage proteins and their mRNAs in suspensor and endosperm preceded synthesis in the embryo proper. We have observed differential accumulation of an array of transcripts in suspensor, megagametophyte, and embryo proper of loblolly pine J.…”

“…In addition, permeation of NH 3 in peribacteroid membrane vesicles was shown to be partially mediated by proteinaceous channels (Niemietz and Tyerman, 2000), raising the question of GmNOD26 involvement in NH 3 flux. Assuming GmNOD26 and other NIPs like PtNIP1;1 flux NH 3 , an immediate role could be envisioned for PtNIP1;1, because embryo maturation is marked by storage protein accumulation and suspensors likely synthesize storage proteins (Panitz et al, 1995;Cairney et al, 2000), both of which may require additional capacity for shuttling nitrogen.…”

“…have structural modifications to facilitate nutrient transport (Schulz and Jensen, 1969). Larger suspensors may serve as a storage tissue, and they appear to be more involved in macromolecular biosynthesis; thereby providing nutritional support for the embryo proper (Yeung and Meinke, 1993;Panitz et al, 1995;Cairney et al, 2000). From a genetic perspective, recently isolated devel-opmental mutants are providing insights into suspensor function (for review, see Schwartz et al, 1997;Yadegari and Goldberg, 1997).…”