The plastid skeleton: a source of ideas in the nano range

Abstract

152. But they can also change their shape, that is, they can grow and divide. For a long time it was not known what causes these changes, what structure gives the organelles their shape, and what is responsible for changes in that shape. We biologists were able to demonstrate that the chloroplasts of a moss, the spreading earthmoss (Physcomitrella patens), contain five different so-called FtsZ proteins. When we mark these FtsZ proteins using genetic methods by attaching the bright-green fluorescing GFP protein, microscopic images reveal protein filaments and networks 153. It is noticeable that each FtsZ protein is characterized by a pattern that is different from the other four. These patterns are reminiscent of the cell skeleton that occurs in the cytoplasm of every higher cell (eukaryotic cell), giving it its shape and helping it to change its form. For this reason we proposed the analogous term “plastid skeleton” for these FtsZ filaments in the chloroplasts. Microbiologists have been able to demonstrate that similar cell skeletons occur in bacteria, determining their shape and triggering division. Here too, an FtsZ protein is involved. When this is mutated in bacteria, they take on the shape of a thread at certain temperatures. This is also where the abbreviation FtsZ comes from: filamentous temperature-sensitive mutant Z. This finding is particularly exciting from the point of view of evolution, because the chloroplasts of plants evolved from bacteria about one and a half billion years ago. We can therefore surmise that the FtsZ molecules of bacteria are similar to those of chloroplasts not only in their composition and sequence but also in their function. In this research project, biologists from Freiburg University and engineers from Stuttgart University have got together in order to uncover the secrets of the plastid skeleton in mosses. This is very challenging, because the structures investigated The plastid skeleton: a source of ideas in the nano range