Embryology and evolution 1920-1960: worlds apart?

During the early part of the 20th century most embryologists were skeptical about the significance of Mendelian genetics to embryological development. A few embryologists began to study the developmental effects of Mendelian genes around 1940. Such work was a necessary step on the path to modern developmental biology. It occurred during the time when the Evolutionary Synthesis was integrating Mendelian and population genetics into a unified evolutionary theory. Why did the first embryological geneticists begin their study at that particular time? One possible explanation is that developmental genetics was a potential avenue of alliance between embryology and evolutionary biology, two fields that had been separated since the 1890s. To assess this possible motive it is necessary to explore the methodological contrasts that obtained between embryology and both Mendelian-chromosomal genetics and neo-Darwinian evolutionary theory. Some of these contrasts persist to the present day.     

Patterning in the cellular slime moulds

The aim of the present article is to derive and illustrate in a simple form some of the important concepts in developmental biology. The development of the cellular slime mouldDictyostelium discoideum is an ideal model system for this purpose. I will outline the development of this organism at its multicellular stages and review some relevant studies focusing on the control of cell differentiation and pattern formation while deriving some key concepts in the current thinking about the control of development.     

A New Insight into Sanger’s Development of Sequencing: From Proteins to DNA, 1943–1977

Fred Sanger, the inventor of the first protein, RNA and DNA sequencing methods, has traditionally been seen as a technical scientist, engaged in laboratory bench work and not interested at all in intellectual debates in biology. In his autobiography and commentaries by fellow researchers, he is portrayed as having a trajectory exclusively dependent on technological progress. The scarce historical scholarship on Sanger partially challenges these accounts by highlighting the importance of professional contacts, institutional and disciplinary moves in his career, spanning from 1940 to 1983. This paper will complement such literature by focusing, for the first time, on the transition of Sanger’s sequencing strategies from degrading to copying the target molecule, which occurred in the late 1960s as he was shifting from protein and RNA to DNA sequencing, shortly after his move from the Department of Biochemistry to the Laboratory of Molecular Biology, both based in Cambridge (UK). Through a reinterpretation of Sanger’s papers and retrospective accounts and a pioneering investigation of his laboratory notebooks, I will claim that sequencing shifted from the working procedures of organic chemistry to those of the emergent molecular biology. I will also argue that sequencing deserves a history in its own right as a practice and not as a technique subordinated to the development of molecular biology or genomics. My proposed history of sequencing leads to a reappraisal of current STS debates on bioinformatics, biotechnology and biomedicine.     

Continuity and change: paradigm shifts in neural induction

The problem of "primary embryonic induction" was one of the first areas of developmental biology to become "molecularized." What had been seen as an intractable series of problems became amenable to the techniques of Northern blotting, ectopic RNA insertion, and in situ hybridization. These molecular analyses showed that some of the fundamental concepts of primary embryonic induction concluded by experimental embryologists were false. First, primary embryonic induction was not primary. The organizer tissue, itself, was the product of a prior induction. Second, the neural fate of cells was not being induced. Rather, the epidermal fate was induced and the neural state was the default, uninduced, fate of ectodermal tissues. Third, primary embryonic induction was not something unique to vertebrates. Rather, the ventral neural cord of insects formed using the same mechanisms as the dorsal neural tube of vertebrates. Fourth, the brain formed in a matter distinctly different from that the spinal cord. Despite these differences, there has been a clear and strong continuity between the experimental embryological tradition and the molecular genetic tradition, and these new results are seen by many contemporary developmental geneticists as strengthening, rather than destroying, the older science.     

Offerings from an urchin

There is a natural curiosity about how organisms give rise to offspring like themselves through a series of reproducible developmental events and how, once mature, these offspring mate and continue the process giving rise the next generation. In the mid-1800 s investigators started using gametes and embryos to explore this process. Although the observations and experimental approaches changed over time, embryologists and developmental biologists after them, sought understanding of development and inheritance through the study of gametes and embryos. It is argued here that in their quests to understand these processes embryologists made major conceptual advances that were seminal to the origins of genetics and to the origins of molecular biology. Furthermore these advances derived from the distinct perspective of those investigators with focused interest on the development of the organism. In this essay fundamental discoveries that originated with the sea urchin embryo as an experimental system are used to illustrate this position. The sea urchin has a long and uninterrupted history as a model organism that helped prepare the ground for the emergence of genetics and contributed important aspects to understanding of the central dogma of molecular biology. As molecular biology came of age new concepts and technology of the discipline were transformative for developmental biology and to this day the reciprocal inductive interactions between molecular biology and developmental biology continue to revitalize each other.     

August Weismann on Germ-Plasm Variation

August Weismann is famous for having argued against the inheritance of acquired characters. However, an analysis of his work indicates that Weismann always held that changes in external conditions, acting during development, were the necessary causes of variation in the hereditary material. For much of his career he held that acquired germ-plasm variation was inherited. An irony, which is in tension with much of the standard twentieth-century history of biology, thus exists – Weismann was not a Weismannian. I distinguish three claims regarding the germ-plasm: (1) its continuity,(2) its morphological sequestration, and (3) its variational sequestration. With respect to changes in Weismann's views on the cause of variation, I divide his career into four stages. For each stage I analyze his beliefs on the relative importance of changes in external conditions and sexual reproduction as causes ofvariation in the hereditary material. Weismann believed, and Weismannism denies, that variation, heredity, and development were deeply intertwined processes. This article is part of a larger project comparing commitments regarding variation during the latter half of the nineteenth century. This revised version was published online in July 2006 with corrections to the Cover Date.     

The genius of Wilhelm Hofmeister: the origin of causal-analytical research in plant development

Friederich Wilhelm Benedikt Hofmeister (1824-1877) stands as one of the true giants in the history of biology and belongs in the same pantheon as Darwin and Mendel. Yet by comparison, he is virtually unknown. If he is known at all, it is for his early work on flowering plant embryology and his ground-breaking discovery of the alternation of generations in plants, which he published at age 27 in 1851. Remarkable as the latter study was, it was but a prelude to the more fundamental contributions he was to make in the study of plant growth and development expressed in his books on plant cell biology (Die Lehre von der Pfanzenzelle, 1867) and plant morphology (Allgemeine Morphologie der Gewächse, 1868). In this article we review his remarkable life and career, highlighting the fact that his scientific accomplishments were based largely on self-education in all areas of biology, physics, and chemistry. We describe his research accomplishments, including his early embryological studies and their influence on Mendel's genetic studies as well as his elucidation of the alternation of generations, and we review in detail his cell biology and morphology books. It is in the latter two works that Hofmeister the experimentalist and biophysicist is most manifest. Not only did Hofmeister explore the mechanisms of cytoplasmic streaming, plant morphogenesis, and the effects of gravity and light on their development, but in each instance he developed a biophysical model to integrate and interpret his wealth of observational and experimental data. Because of the lack of attention to the cell and morphology books, Hofmeister's true genius has not been recognized. After studying several evaluations of Hofmeister by contemporary and later workers, we conclude that his reputation became eclipsed because he was so far ahead of his contemporaries that no one could understand or appreciate his work. In addition, his basically organismic framework was out of step with the more reductionistic cytogenetic work that later came in vogue. We suggest that the translation of the cell and morphology books in English would help re-establish him as one of the most notable scientists in the history of plant biology.     

Greetings from the new Editor-in-Chief

I am very pleased to take over the position of Editor-in-Chiefof Plant and Cell Physiology, the most prestigious and trulyinternational journal focusing on physiology, biotechnology,biophysics, chemistry, genetics, molecular biology, gene engineeringand cell biology of plants and microorganisms. I will startby saying that I will do my best to improve the quality of     

Deep diving in the blood stem cell‐ome

Defining the functional distinctions between cells comprising the bone marrow has yielded fundamental insights into lineage ordering and drivers of blood cell production. A novel, highly granular and multi‐dimensional molecular characterization of functional subsets of hematopoietic stem‐ and progenitor cells recently published in Cell Stem Cell (Cabezas‐Wallscheid et al, 2014 ) will serve as a landmark and treasure trove for unanticipated insights into basic biology and the development of future targeted medicine.     

Last judgment: the visionary biology of J.B.S. Haldane

This paper seeks to reinterpret the life and work of J. B. S. Haldane by focusing on an illuminating but largely ignored essay he published in1927, “The Last Judgment” – the sequel to his better known work, Daedalus (1924). This astonishing essay expresses a vision of the human future over the next 40,000,000 years, one that revises and updates Wellsian futurism with the long range implications of the “new biology” for human destiny. That vision served as a kind of lifelong credo, one that infused and informed his diverse scientific work, political activities, and popular writing, and that gave unity and coherence to his remarkable career. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular biology of extremophiles: recent progress on the hyperthermophilic archaeon Sulfolobus

Extremophiles are microorganisms that flourish in habitats of extreme temperature, pH, salinity, or pressure. All extreme environments are dominated by microorganisms belonging to Archaea, the third domain of life, evolutionary distinct from Bacteria and Eucarya. Over the past few years the biology of extremophilic Archaea has stimulated a lot of interest, aimed at understanding at molecular level the adaptation to their life conditions, as well as their evolutionary relationships to other organisms. Here, we review recent insights in the molecular biology of thermoacidophilic Archaea of the genus Sulfolobus, which has been used as a model system for biochemical, structural, and genetic studies in Archaea and extremophiles in general. With the recent completion of the genome sequence of Sulfolobus solfataricus it is expected that these organisms will contribute new discoveries in the near future. This revised version was published online in August 2006 with corrections to the Cover Date.     

The molecular biology of schistosomes

Twenty years ago, an article by Carter and Colley was published in an early issue of this journal. The report outlined pioneering studies by several laboratories into schistosome molecular biology and molecular genetics. To commemorate that prescient report and, in like fashion, to provide a brief (and non-comprehensive) synopsis of progress in this field up to the present time, I will outline some key aspects of the molecular biology of schistosomes that have been reported in the intervening years.     

Naturalists, Molecular Biologists, and the Challenges of Molecular Evolution

Biologists and historians often present natural history and molecular biology as distinct, perhaps conflicting, fields in biological research. Such accounts, although supported by abundant evidence, overlook important areas of overlap between these areas. Focusing upon examples drawn particularly from systematics and molecular evolution, I argue that naturalists and molecular biologists often share questions, methods, and forms of explanation. Acknowledging these interdisciplinary efforts provides a more balanced account of the development of biology during the post-World War II era. This revised version was published online in July 2006 with corrections to the Cover Date.     

Zebrafish as the Best Vertebrate Model for Development Studies

从八十年代初开始的、通过突变体分离早期胚胎发育基因的研究,揭示了无脊椎动物果蝇形态发生的分子机制,成为１９９５年诺贝尔生理或医学奖的主要内容,同时也标志着发育生物学已经成为生物学的带头学科。该成果的取得得益于果蝇具备发育生物学研究模型的特点,即可同时进行胚胎学和发育遗传学研究。在脊椎动物发育生物学研究方面,由于缺少适当的研究模型,有关早期胚胎发育基因表达调控的研究始终未获突破性进展。包括小鼠、鸡、爪蟾等在内的一些脊椎动物都只适用于胚胎学或者遗传学某一学科的研究,均不是理想的发育生物学研究模型。一种小型的鲤科鱼———斑马鱼,逐渐成为发育生物学研究的最佳脊椎动物模型。它光周期产卵,卵大,胚胎在体外发育,胚胎发育速度快,早期胚胎完全透明,这些特点使它成为很好的脊椎动物胚胎学研究模型;同时,它个体小,产卵量大,产卵周期短,单倍体、雌核发育二倍体的制作和突变体的获得均较容易,精子可以冷冻保存,所有这些特点又使斑马鱼非常适合于发育遗传学研究。本文将详细论述斑马鱼作为脊椎动物发育生物学研究模型的特点,以及作为模型动物正在进行的有关工作。     

The value of applying molecular biology tools in environmental engineering: Academic and industry perspective in the USA

The integration of molecular biology tools in environmental engineering is a challenge. We discuss our views on the following four critical issues: (i) faculty career development, (ii) tool standardization, (iii) teaching, and (iv) the application of molecular biology tools in practice. For (i), we suggest that administrators and faculty need to understand the special challenges inherent to research and teaching within this highly interdisciplinary area. Furthermore, we suggest preparing two white papers aimed at educating administrators in universities and agencies. For (ii), we conclude that, because molecular biology tools are still in a state of rapid development, proposing standards at this time is premature. In the future, standards for widely applied tools should be in an on-line, peer-reviewed format. Concerning (iii), we believe that molecular biology should be taught only to the degree needed to achieve program goals. For example, environmental engineering practitioners only need to know the vocabulary and basic concepts of molecular biology tools, not be experts at doing them hands on. To help engineering students gain the right level and type of information, learning modules should be developed for them. Finally, although engineering successes applying molecular biology tools are available (iv), the biggest value will come when the tools are fully integrated with practice. Therefore, we encourage the creation of a demonstration project to document the value of applying molecular biology tools in environmental engineering. This revised version was published online in June 2006 with corrections to the Cover Date.     

Human L1 retrotransposition: insights and peculiarities learned from a cultured cell retrotransposition assay

Long Interspersed Nuclear Elements (L1s or LINEs) are the most abundant retrotransposons in the human genome, and they comprise approximately 17% of DNA. L1 retrotransposition can be mutagenic, and deleterious insertions both in the germ-line and in somatic cells have resulted in disease. Recently, an assay was developed to monitor L1 retrotransposition in cultured human cells. This assay, for the first time, now allows for a systematic study of L1 retrotransposition at the molecular level. Here, I will review progress made in L1 biology during the past three years. In general, I will limit the discussion to studies conducted on human L1s. However, interesting parallels to rodent L1s and other non-LTR retrotransposons also will be discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

'Molecules and monkeys': George Gaylord Simpson and the challenge of molecular evolution

In this paper, I analyze George Gaylord Simpson's response to the molecularization of evolutionary biology from his unique perspective as a paleontologist. I do so by exploring his views on early attempts to reconstruct phylogenetic relationships among primates using molecular data. Particular attention is paid to Simpson's role in the evolutionary synthesis of the 1930s and 1940s, as well as his concerns about the rise of molecular biology as a powerful discipline and world-view in the 1960s. I argue that Simpson's belief in the supremacy of natural selection as the primary driving force of evolution, as well as his view that biology was a historical science that seeks ultimate causes and highlights contingency, prevented him from acknowledging that the study of molecular evolution was an inherently valuable part of the life sciences.     

Systematics and evolutionary biology of the fern genusHymenasplenium (Aspleniaceae)

In Aspleniaceae,Hymenasplenium is a well-defined group with dorsiventral creeping rhizomes. Members ofHymenasplenium are widely distributed in the tropic zones of the world and have great variation in morphology and ecolgy, making it a good model group for plant systematics and evolutionary biology. I have worked on this group using techniques such as comparative morphology, ecology, cytology (for examining chromosomes and reproductive modes), phytochemistry and molecular biology. I considered the evolution of various phenetic characters based on a molecular phylogenetic tree which I recently obtained from sequence comparisons ofrbcL. In this paper, I will summarize the results. Recipient of the Botanical Society Award for Young Scientists, 1993.     

Speciation on islands: what are we learning?

Systematics and the Origin of Species from the Viewpoint of a Zoologist has remained an essential text on the bookshelves of evolutionary biologists since it was first published. Here, I expand upon several topics touched upon by Ernst Mayr to look at how our thinking has evolved, and is evolving, with particular reference to molecular phylogenetic studies on islands. At the time of publication, apart from the fossil record, inferences of temporal trends or patterns could only be speculative, deduced from the distributions of species and the patterns that these present. Much like the subject material itself, evolutionary biology evolves as a discipline, with an increasing availability of tools and resources. The development of molecular phylogenetics and molecular markers has given biologists a new window on the past and, as such, the ideas and explanations of Mayr have become more accessible to testing. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 47–52.