Cell-Cell Channels and Their Implications for Cell Theory
Frantisek Baluska*, Dieter Volkmann and Peter W. Barlow
Cells show diverse appearances and sizes, ranging from some 30 nanometers up to several meters in length. Besides the classical prokaryotic and eukaryotic cells, there are also very bizarre cells such as the highly reduced symbiotic mitosomes which lack DNA. Other examples of extremely small cells in the nanometre range are the mycosomes and nanobacteria. On the other hand, there are huge eukaryotic cells, the size of which can reach up to several meters. Most of these are multinucleate (coenocytic) due to mitotic divisions not having been followed by cytokinesis. Moreover, cells at all levels of cellular complexity show an inherent tendency to form cell-cell channels. The most conspicuous example is the plant ‘supercell’ where all the cells of the plant body are permanently connected via plasmodesmata. In the last year, the first reports of similar cell-cell channels between animal cells have been published. Moreover, fungal cells fuse together into supracellular mycelia, even exchanging their motile nuclei. This phenomenon is also known for plant cells. Intriguingly, transcellularly moving fungal nuclei communicate with their mating partners via pheromone-like signaling mechanisms.
Already in 1892 Julius Sachs was aware of most of the problems associated with the Cell Theory, which in fact survive until the present. Sachs proposed the Energide concept, postulating that it is the nucleus and its protoplasm which represent the vital unit of living matter within a supracellular construction, while the cell periphery is only a secondary structure generated by the active Energide for its shelter and protection. Recently, we elaborated the Cell Body concept which explains how and why the nucleus and the microtubular cytoskeleton have become merged together to build a coherent and universal unit of eukaryotic life which is autonomous and can synthesize the rest of the cell. However, there are several problems with the term Cell Body as it is sometimes used in other meanings. Here we show that the Energide concept of Sachs can be united with the Cell Body concept. Moreover, we agree with Julius Sachs that the term Energide better invokes the unique properties of this universal unit of supracellular living matter endowed with the vital energy.