Protoplasma

Using a heterologous myosin antibody raised against the whole molecule of bovine muscle myosin, we have identified a myosin-like protein in maize. Immunoblots of subcellular fractions isolated from roots identified one distinct band at about 210 kDa in the microsomal protein fraction and one band at about 180 kDa in the soluble protein fraction. Indirect immunofluorescence was performed using maize root apex sections to reveal endocellular distributions of the myosin-like protein. Both diffuse and particulate labelling patterns were observed throughout the cytoplasm of all root cells. In mitotic cells, myosin-like protein was excluded from spindle regions. Amyloplast surfaces were labelled prominently in cells of the root cap statenchyma and in all root cortex cells. On the other hand, myosin-like protein was prominently enriched at cellular peripheries in cells of the pericycle and outer stele in the form of continuous peripheral labelling. From all root apex tissues, phloem elements showed the most abundant presence of myosinlike protein.

Protoplasts obtained from cell suspensions of an anthocyanin synthesizing strain ofDaucus carota cv. “Rote Riesen”, cultured on a modified Murashige and Skoog medium (MS) have been induced to regenerate cell walls, and divide repeatedly to form masses of callus. Techniques have been substantially refined, and optimal conditions for the isolation of protoplasts have been established. An optimal protoplast yield of 80–90% was obtained by treating the cells with 1.5% cellulase (pH 5.0) for 4.5 hours in a gently shaking water-bath maintained at 33 °C. The protoplasts when plated in the agar-solidified medium regenerated cell walls within 2 days, and first division was observed within 3 days. In addition, they showed irregular elongation, budding and the formation of sub-protoplasts; another phenomenon was the formation of a chain of buds, which either separated from each other or formed a “coenocytic”, tube-like structure. On the agar medium which contained 0.425 M sorbitol, growth slowed down or stopped after 3–4 weeks. In order to obtain further growth, it was necessary to transfer small pieces of agar containing protoplasts on to the top of a fresh medium containing lower amounts (0.2 M) of sorbitol. The protoplasts continued to divide to form cell colonies, and finally masses of callus after 4–5 weeks. In a liquid medium (B5) the protoplasts reacted similarly, they regenerated walls within 2 days and after 2 weeks anthocyanin containing callus was formed. In both media embryo-formation occurred after 6 weeks of culture. By combining the polyethylene glycol and the high pH fusion techniques intergeneric fusion was achieved between carrot protoplasts and mesophyll protoplasts from haploidNicotiana tabacum cv. “Badischer Burley”. The fused products could be readily identified and isolated by using the difference in colour as the visual markers. Conditions for the culture of these fused protoplasts are being worked out.

Primary plastids originated from a free-living cyanobacterial ancestor and possess their own genomes—probably a few DNA copies. These genomes, which are organized in centrally located plastid nuclei (CN-type pt-nuclei), are produced from preexisting plastids by binary division. Ancestral algae with a CN-type pt-nucleus diverged and evolved into two basal eukaryotic lineages: red algae with circular (CL-type) pt-nuclei and green algae with scattered small (SN-type) pt-nuclei. Although the molecular dynamics of pt-nuclei in green algae and plants are now being analyzed, the process of the conversion of the original algae with a CN-type pt-nucleus to red algae with a CL-type one has not been studied. Here, we show that the CN-type pt-nucleus in the primitive red alga Cyanidioschyzon merolae can be changed to the CL-type by application of drying to produce slight cell swelling. This result implies that CN-type pt-nuclei are produced by compact packing of CL-type ones, which suggests that a C. merolae–like alga was the original progenitor of the red algal lineage. We also observed that the CL-type pt-nucleus has a chain-linked bead-like structure. Each bead is most likely a small unit of DNA, similar to CL-type pt-nuclei in brown algae. Our results thus suggest a C. merolae–like alga as the candidate for the secondary endosymbiont of brown algae.

The intracellular localization of partially O-methylated flavonol glucosides was studied inChrysosplenium americanum leaves using caffeine as stabilizing and visualizing reagent. Electron microscopic observations and chromatographic data indicated that intracellular flavonoids were found to accumulate mainly within the walls of epidermal and mesophyll cells. Various membrane profiles and associated vesicles appeared to be involved in the packaging and channelling of the electron-dense material towards the cell wall. There was no evidence to suggest the participation of chloroplasts in these processes. The significance of flavonoid accumulation in cell walls was discussed in relation to the nature of these compounds and their possible ecophysiological role in this plant.

The biflagellate green algaChlamydomonas can exhibit substrate-associated gliding motility in addition to its ability to swim through a liquid medium. The flagella are the organelles responsible for both forms of whole-cell locomotion although the mechanism in each case is very different. In this study, we demonstrate that the binding of polystyrene microspheres to the flagellar surface ofChlamydomonas initiates clustering of the major flagellar-membrane glycoprotein, which is known to be involved in motility-associated substrate adhesion. In addition, we demonstrate that microsphere binding to the flagellar surface initiates the same transmembrane signaling pathway that is initiated by antibody- or lectin-induced crosslinking of the major flagellar-membrane glycoprotein. In each case, the signaling pathway involves the activation of a calciumdependent protein phosphatase that dephosphorylates a flagellar phosphoprotein known to be associated with the major flagellar-membrane glycoprotein. Bound microspheres are translocated along the flagellar surface at approximately the same velocity as whole-cell gliding motility. Previous observations suggest that microsphere binding and translocation along the flagellar surface may be a reflection of the same force-transducing system responsible for whole-cell gliding motility. In which case, these observations suggest that the transmembrane signaling pathway initiated by crosslinking the major flagellar-membrane glycoprotein is the same one that is activated when the cell contacts a physiological substrate by its flagellar surface.