498 research outputs found
There is more than one way to turn a spherical cellular monolayer inside out: type B embryo inversion in Volvox globator
Full text linkHöhn S, Hallmann A. There is more than one way to turn a spherical cellular monolayer inside out: type B embryo inversion in Volvox globator. BMC Biology. 2011;9(1): 89.Background:
Epithelial folding is a common morphogenetic process during the development of multicellular organisms. In metazoans, the biological and biomechanical processes that underlie such three-dimensional (3D) developmental events are usually complex and difficult to investigate. Spheroidal green algae of the genus Volvox are uniquely suited as model systems for studying the basic principles of epithelial folding. Volvox embryos begin life inside out and then must turn their spherical cell monolayer outside in to achieve their adult configuration; this process is called 'inversion.' There are two fundamentally different sequences of inversion processes in Volvocaceae: type A and type B. Type A inversion is well studied, but not much is known about type B inversion. How does the embryo of a typical type B inverter, V. globator, turn itself inside out?
Results:
In this study, we investigated the type B inversion of V. globator embryos and focused on the major movement patterns of the cellular monolayer, cell shape changes and changes in the localization of cytoplasmic bridges (CBs) connecting the cells. Isolated intact, sectioned and fragmented embryos were analyzed throughout the inversion process using light microscopy, confocal laser scanning microscopy, scanning electron microscopy and transmission electron microscopy techniques. We generated 3D models of the identified cell shapes, including the localizations of CBs. We show how concerted cell-shape changes and concerted changes in the position of cells relative to the CB system cause cell layer movements and turn the spherical cell monolayer inside out. The type B inversion of V. globator is compared to the type A inversion in V. carteri.
Conclusions:
Concerted, spatially and temporally coordinated changes in cellular shapes in conjunction with concerted migration of cells relative to the CB system are the causes of type B inversion in V. globator. Despite significant similarities between type A and type B inverters, differences exist in almost all details of the inversion process, suggesting analogous inversion processes that arose through parallel evolution. Based on our results and due to the cellular biomechanical implications of the involved tensile and compressive forces, we developed a global mechanistic scenario that predicts epithelial folding during embryonic inversion in V. globator
Stable nuclear transformation of Eudorina elegans
Full text linkLerche K, Hallmann A. Stable nuclear transformation of Eudorina elegans. BMC Biotechnology. 2013;13(1): 11.UNLABELLED: ABSTRACT: BACKGROUND: A fundamental step in evolution was the transition from unicellular to differentiated, multicellular organisms. Volvocine algae have been used for several decades as a model lineage to investigate the evolutionary aspects of multicellularity and cellular differentiation. There are two well-studied volvocine species, a unicellular alga (Chlamydomonas reinhardtii) and a multicellular alga with differentiated cell types (Volvox carteri). Species with intermediate characteristics also exist, which blur the boundaries between unicellularity and differentiated multicellularity. These species include the globular alga Eudorina elegans, which is composed of 16-32 cells. However, detailed molecular analyses of E. elegans require genetic manipulation. Unfortunately, genetic engineering has not yet been established for Eudorina, and only limited DNA and/or protein sequence information is available. RESULTS: Here, we describe the stable nuclear transformation of E. elegans by particle bombardment using both a chimeric selectable marker and reporter genes from different heterologous sources. Transgenic algae resistant to paromomycin were achieved using the aminoglycoside 3'-phosphotransferase VIII (aphVIII) gene of Streptomyces rimosus, an actinobacterium, under the control of an artificial promoter consisting of two V. carteri promoters in tandem. Transformants exhibited an increase in resistance to paromomycin by up to 333-fold. Co-transformation with non-selectable plasmids was achieved with a rate of 50 - 100%. The luciferase (gluc) gene from the marine copepod Gaussia princeps, which previously was engineered to match the codon usage of C. reinhardtii, was used as a reporter gene. The expression of gluc was mediated by promoters from C. reinhardtii and V. carteri. Heterologous heat shock promoters induced an increase in luciferase activity (up to 600-fold) at elevated temperatures. Long-term stability and both constitutive and inducible expression of the co-bombarded gluc gene was demonstrated by transcription analysis and bioluminescence assays. CONCLUSIONS: Heterologous flanking sequences, including promoters, work in E. elegans and permit both constitutive and inducible expression of heterologous genes. Stable nuclear transformation of E. elegans is now routine. Thus, we show that genetic engineering of a species is possible even without the resources of endogenous genes and promoters
Advances in Genetic Engineering of Microalgae
No full textHallmann A. Advances in Genetic Engineering of Microalgae. In: Grand Challenges in Algae Biotechnology. Grand Challenges in Biology and Biotechnology. Cham: Springer International Publishing; 2020: 159-221
Stable nuclear transformation of Gonium pectorale
Full text linkLerche K, Hallmann A. Stable nuclear transformation of Gonium pectorale. BMC Biotechnology. 2009;9(1): 64.BACKGROUND: Green algae of the family Volvocaceae are a model lineage for studying the molecular evolution of multicellularity and cellular differentiation. The volvocine alga Gonium is intermediate in organizational complexity between its unicellular relative, Chlamydomonas, and its multicellular relatives with differentiated cell types, such as Volvox. Gonium pectorale consists of ~16 biflagellate cells arranged in a flat plate. The detailed molecular analysis of any species necessitates its accessibility to genetic manipulation, but, in volvocine algae, transformation procedures have so far only been established for Chlamydomonas reinhardtii and Volvox carteri. RESULTS: Stable nuclear transformation of G. pectorale was achieved using a heterologous dominant antibiotic resistance gene, the aminoglycoside 3'-phosphotransferase VIII gene (aphVIII) of Streptomyces rimosus, as a selectable marker. Heterologous 3'- and 5'-untranslated flanking sequences, including promoters, were from Chlamydomonas reinhardtii or from Volvox carteri. After particle gun bombardment of wild type Gonium cells with plasmid-coated gold particles, transformants were recovered. The transformants were able to grow in the presence of the antibiotic paromomycin and produced a detectable level of the AphVIII protein. The plasmids integrated into the genome, and stable integration was verified after propagation for over 1400 colony generations. Co-transformants were recovered with a frequency of ~30-50% when cells were co-bombarded with aphVIII-based selectable marker plasmids along with unselectable plasmids containing heterologous genes. The transcription of the co-transformed, unselectable genes was confirmed. After heterologous expression of the luciferase gene from the marine copepod Gaussia princeps, which was previously engineered to match the codon usage in C. reinhardtii, Gonium transformants show luciferase activity through light emission in bioluminescence assays. CONCLUSION: Flanking sequences that include promoters from C. reinhardtii and from V. carteri work in G. pectorale and allow the functional expression of heterologous genes, such as the selectable marker gene aphVIII of S. rimosus or the co-transformed, codon-optimized G. princeps luciferase gene, which turned out to be a suitable reporter gene in Gonium. The availability of a method for transformation of Gonium makes genetic engineering of this species possible and allows for detailed studies in molecular evolution using the unicellular Chlamydomonas, the 16-celled Gonium, and the multicellular Volvox
Lumineszenz - Coole Leuchterscheinungen in der Biologie und anderswo
No full textHallmann A. Lumineszenz - Coole Leuchterscheinungen in der Biologie und anderswo. PdN Biologie. 2011;60:4-11
Experienced developers of multicellularity - the Volvocales
No full textHallmann A. Experienced developers of multicellularity - the Volvocales. Bioforum Europe. 2003;6:326-328
Fortbewegung bei Mikroorganismen und Keimzellen
No full textHallmann A. Fortbewegung bei Mikroorganismen und Keimzellen. PdN Biologie. 2012;61:7-13
Die Evolution zur Vielzelligkeit. Grünalgen als "Wiederholungstäter"
No full textHallmann A. Die Evolution zur Vielzelligkeit. Grünalgen als "Wiederholungstäter". BUZ. 2003;(215):63-64
Algen als Bioindikatoren und Wasserreiniger
No full textHallmann A. Algen als Bioindikatoren und Wasserreiniger. PdN Biologie. 2013;62:27-33
Vom Einzeller zum Vielzeller. Die Rolle der Extrazellulären Matrix
No full textHallmann A. Vom Einzeller zum Vielzeller. Die Rolle der Extrazellulären Matrix. Bioforum. 2002;2002(1: Sonderausgabe Zellbiologie):14-16
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