Localization of calcium ions in wounded characean internodal cells

Abstract

Ca# + was localized in chemically injured internodal cells of the characean alga Nitella flexilis (L.) Ag. using alizarin red and antimonate precipitation. The presence of Ca# + in the antimonate precipitates was verified by X-ray analysis and EGTA chelation. Callose-containing amorphous wound walls were induced by 0n1 m chlortetracycline (CTC) and cellulosic fibrillar wound walls were induced by 50 m CaCl # . Numerous precipitates were found in the amorphous wound walls and in the adjacent cytoplasm. Precipitates were mainly localized in single membrane-bound cisternae, probably of the endoplasmic reticulum, which accumulate at the wound and become a component of the amorphous wound wall via membrane fusion. In fibrillar wound walls, which do not contain membranous residues, precipitate density was significantly lower and similar to that in the secondary cell wall.The data suggest that the high Ca# + content of amorphous wound walls is due to incorporation of cytoplasmic Ca# + stores. The possible function of amorphous wound walls in maintaining cellular Ca# + homeostasis is discussed.

Actin‐dependent deposition of putative endosomes and endoplasmic reticulum during early stages of wound healing in characean internodal cells

“…Earlier studies suggested that the ER plays an important role during wound healing in characean internodal and other cells (Foissner 1998 and references therein). In unwounded internodes, the ER consists of a mesh‐like cortical ER sandwiched between the plasma membrane and the stationary chloroplast files and tubular branched cisternae that move rapidly along the subcortical actin filament bundles (Fig.…”

“…The deposition of huge membrane‐bound compartments has been described from electron micrographs of wounds induced by Ca 2+ ionophores (Foissner 1988a, 1991). These cisternae were presumed to be of ER origin, and cytochemical analysis indicated that they were heavily loaded with Ca 2+ (Foissner 1998). During this study, we used CLSM of DiOC 6 ‐labelled cells and proved that these cisternae are indeed of ER origin and that they are actively transported towards wounds and then deposited.…”

The characean internodal cell as a model system for studying wound healing

“…These ER cisternae are heavily loaded with calcium, as visualized by precipitation with antimonate (Fig. 4F) or staining with alizarin red (Foissner, 1998). ER deposition is thus responsible for the high calcium content of the amorphous wound walls, which is also evident from the intense chlortetracycline-fluorescence (Foissner, 1988a) indicating membrane-bound calcium (Fig.…”

“…6D). The ER cisternae are heavily loaded with calcium and their deposition into the extracytoplasmic space could be an efficient emergency reaction to Ca 2+ overload (Foissner, 1998).…”

“…Calcium was localized by fixation in 5 % glutaraldehyde containing 2 % potassium antimonate and postfixation in 1 % OsO 4 and 1.5 % potassium antimonate precipitation with antimonate as described in (Foissner, 1998).…”