Functional and Structural Differences among Proplastids, as Seen by Immunogold Staining and Electron Microscopy

The proliferation of amyloplasts in meristematic cells of developing stolons of potato and apple callus: Progenitors of proplastids

“…Norin 1) were grown in pots as described elsewhere (Akita and Sagisaka, 1995). Developing apices of stolons, which were about 2 mm in diameter and 2 mm in length, were cut vertically in the central region and immediately fixed in 2.5% glutaraldehyde in 0.05 mol L À1 phosphate buffer, pH 7.3, overnight at room temperature.…”

“…Norin I, as described previously (Akita and Sagisaka, 1995). The antigen, GBSSI, was isolated as described by Vos-Scheperkeuter et al (1986).…”

“…Norin 1 were fixed in 0.05 mol L À1 cacodylate buffer, pH 7.4, that contained 4% paraformaldehyde, 0.25% glutaraldehyde and 0.06 mol L À1 sucrose for 5 h at 0 1C and then for 1 h at 22 1C, as described elsewhere (Akita and Sagisaka, 1995). Subsequent washing in the same buffered solution, dehydration in a graded ethanol series and soaking in mixtures (1:1 and 1:2, v/v) of ethanol and LR-White resin (Sigma Chemical Co., St. Louis, MO) were performed as described (Akita and Sagisaka, 1995). The resin contained benzoyl peroxide (at the concentration specified by the manufacturer).…”

“…The key components of the A pathway, the y proplastids (Akita and Sagisaka, 1995;Sagisaka et al, 1999) and the dividing y proplastids, accounted for 25.5% of the total organelles (Table 1, type b; Figures 1, 3, 4). Immunogold staining indicated that the intrinsic genetic material of amyloplasts, derived from stem cells, had already been transferred to juvenile plastids that were growing at the apices of stolons (Figure 3).…”

“…In meristematic tissues (Marinos, 1967;Possingham, 1980;Possingham and Lawrence, 1983;Sagisaka and Akita, 1994) and developing pollen grains (Ameele, 1982;Nepi et al, 1996;Pacini et al, 1992), cells are rich in proplastids (formed via the A pathway) that are heterogeneous in terms of ultrastructure and metabolic activity (Akita and Sagisaka, 1995). These proplastids can be divided in terms of their development into younger ones (y proplastids) and older ones (o proplastids) (Akita and Sagisaka, 1995;Sagisaka et al, 1999). The former proplastids are primary products of the division of mother plastids in moss (Frey-Wyssling and Mühlethaler, 1965;Maltzahn von and Mühletha-ler, 1962) and woody plants (Sagisaka, 1991a(Sagisaka, , b, 1992, and the y proplastid is the starting organelle in the A pathway.…”