Trafficking of Starch Synthase from the Cytosol to Functional Sites in Younger and Older Proplastids in Developing Stolons of Potato

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

“…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). The absence of starch synthase in proplastids that contained no starch granules was consistent with the properties of y proplastids (Figure 4; Akita and Sagisaka, 1995;Sagisaka et al, 1999).…”

“…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.…”

Tobacco plants respond to the constitutive expression of the tospovirus movement protein NSM with a heat‐reversible sealing of plasmodesmata that impairs development

“…In addition, some transient starch was present in the sink leaf chloroplasts ( Figure 3a) and even in the proplastids in the ribmeristem (Figure 2c,g). Proplastids in apices of developing potato stolons contain enzymes for starch synthases (Akita and Sagisaka, 1995 10 ; Sagisaka et al, 1999), indicating that proplastid starch is synthesized from source-leaf-derived carbohydrates. In the WT tobacco plants the starch grains in the proplastids of the ribmeristem (Figure 2c,g) may therefore represent imported carbohydrates.…”