The centriole and the cell

The endosymbiotic theory of the origin of the centriole is found lacking as no DNA has been found in the structure. The centriole is related to the ribosome in that it is a structure nucleated by RNA. This RNA (morphic) has the property of localizing itself at the site of the old centriole before nucleating a new one. The implication of this property of the localization of RNA is discussed with respect to the way the eukaryotic cell determines its shape.     

The chitin-glucan complex inSaccharomyces cerevisiae

The content of glucosamine in the walls of daughter (without bud scars) and mother (multiscar) cells ofSaccharomyces cerevisiae was examined in a control and after treatment with dilute alkali, acid and buffer. The occurrence of chitin in the bud and birth scars is discussed. The results of IR and X-ray analysis of cell-wall fractions indicate the presence of α-chitin which is a part of the chitin-glucan complex. The size of the crystallite of α-chitin in this complex is about 60 Å.     

Cell division: The renaissance of the centriole

Centrioles are located at the center of the cytoskeleton and duplicate exactly once per cell cycle. Recent studies suggest that centrioles are required for the organization of a functional centrosome and that centriole assembly requires both gamma- and delta-tubulin.     

The centriole cycle in the amoebae of the myxomycetePhysarum polycephalum

Summary In the amoebae of the myxomycetePhysarum polycephalum, procentrioles are formed on the anterior and posterior centrioles in early prophase. Although the relative position of the parental and procentrioles is fixed, all relative positions of the daughter and parental centrioles were observed. During the different stages of mitosis daughter centrioles elongate and acquire anterior satellites, one of the characteristic features of the anterior centrioles. All other anterior morphological characteristics appear only in telophase and early reconstruction stages. In contrast to the parental posterior centrioles, which do not change morphologically during the successive mitotic stages, the parental anterior centrioles lose their morphological characteristics in late prophase and early prometaphase and then acquire the morphological features characteristic of the posterior centrioles. Thus, the following maturation scheme is suggested: a procentriole becomes an anterior centriole during the first mitosis and a posterior centriole during the second mitosis. Since posterior features are maintained during mitosis, the posterior centriole corresponds to the final state of centriole maturation.     

The insect centriole: A land of discovery

Centrioles are involved in the formation of cilia and flagella and in the organization of the centrosome, the main microtubule-organizing center of the cell. Since structural and functional centriole aberrations can contribute to several human diseases, these organelles have recently focused the attention of cell biologists. Here, we review data on the insect centrioles, reporting non-canonical aspects of their behaviour, function and architecture. These findings that represent obvious exceptions to the established rule might contribute to advance our understanding in the formation and the function of centrioles.     

Mating reaction inSaccharomyces cerevisiae

The effect of proteolytic enzymes on sexual agglutinability of haploid cells of the yeastSaccharomyces cerevisiae was examined. Sexual agglutinability of cells of botha and α types was lost on treatment with alkaline protease and two kinds of neutral proteases ofBacillus subtilis, pronase and α-chymotrypsin. Agglutinability of α type cells was lost after treatment with acid protease ofRhizopus chinensis and trypsin, but that ofa type cells was not. These results indicate that the sex-specific substance responsible for the sexual agglutination (agglutination factor) ina type cells differs from that in α type cells. Agglutination factors were solubilized from cell-wall fractions of both mating types by Glusulase treatment. These crude factors specifically inhibited the agglutinability of cells of the opposite mating type with little effect on the agglutinability of cells of the same mating type.