Localization of myocin in Micrasterias cells by immunoelectron microscopy

Abstract

The unicellular green alga Micrasterias has a very differentiated form and is an excellent object for morphogenetic studies. The complicated cytoplasmic streaming system during development is an essential part of the morphogenetic process. The streamings are supported by the acto-myosin system. The presence of actin has been verified by fluorescence microscopy and both the act in-inhibitor cytochalasin B and the myosin inhibitor N-ethylmaleimide clearly inhibit the streamings.This work deals with the localization of myosin in the cell. The methods used were immunoelectronmicroscopy, polyclonal antibody/gold probe, and cryosections. In old semicells, the gold-label localized only in vesicle structures. In growing semicells, the label was abundant in growing lobes, in all levels. In control samples, without antibody, there was no label.According to the results, myosin seems to be part of the dictyosome vesicle membranes. This is clear in the case of old semicells. In growing lobes, the inner structure of the lobes was not preserved very well in cryosections, in any preparation, but there is good evidence that in new, growing parts of the cell there is generally very little material other than cell wall material vesicles. This idea is important for later studies on plant cell growth and cytoplasmic transport.