Molecular Genetics Returns to Basic Postulates of the Florigen Theory

The florigen theory, also known as the hormonal theory of flowering in plants, was put forward by M.Kh. Chailakhyan more than 65 years ago. This theory, reviewed here in its historical progress, gave an impetus to a number of modern genetic and molecular studies of flowering in plants. In turn, results of recent investigations restored to a new level Chailakhyan's ideas about florigen, the hormonal stimulus of flowering.     

"Florigen ": an intriguing concept of plant biology.

"Florigen" is the name that Mikhail Chailakhyan coined in 1937 for the putative hormone regulating flowering. At this concept, plant physiologists arrived following early research concerning the effects of temperature and day length on the transition from vegetative to reproductive stages of plants. The existence of florigen was postulated on the experimental backgrounds involving i) the response of plants to inductive conditions; ii) transmission of a flowering stimulus by grafting; iii) extraction of this stimulus from induced plants. This experimental results showed the existence of florigen at least as concept because they always failed to offer the experimental evidence of its chemical existence. The myth of florigen persisted as long as the end of the Seventies, when physiologists began to consider flowering as a complex process in which various classes of hormones might variously interplay.     

Florigen goes molecular: Seventy years of the hormonal theory of flowering regulation

As early as in 1936, the comprehensive studies of flowering led M.Kh. Chailakhyan to the concept of florigen, a hormonal floral stimulus, and let him establish several characteristics of this stimulus. These studies set up for many years the main avenues for research into the processes that control plant flowering, and the notion of florigen became universally accepted by scientists worldwide. The present-day evidence of genetic control of plant flowering supports the idea that florigen participates in floral signal transduction. The recent study of arabidopsis plants led the authors to conclusion that the immediate products of the gene FLOWERING LOCUS I, its mRNA and/or protein, move from an induced leaf into the shoot apex and evoke flowering therein.     

Methodology in Aristotle’s Theory of Spontaneous Generation

Aristotle’s theory of spontaneous generation offers many puzzles to those who wish to understand his theory both within the context of his biology and within the context of his more general philosophy of nature. In this paper, I approach the difficult and vague elements of Aristotle’s account of spontaneous generation not as weaknesses, but as opportunities for an interesting glimpse into the thought of an early scientist struggling to reconcile evidence and theory. The paper has two goals: (1) to give as charitable and full an account as possible of what Aristotle’s theory of spontaneous generation was, and to examine some of its consequences; and (2) to reflect on Aristotle as a scientist, and what his comments reveal about how he approached a difficult problem. In particular, I propose that the well-recognized problem of the incompatibility between Aristotle’s concept of spontaneity and his theory of spontaneous generation presents an opportunity for insight into his scientific methodology when approaching ill-understood phenomena.     

Problems of Growth and Development in the Studies by M.Kh. Chailakhyan

Main vistas of Academician M.Kh. Chailakhyan's inquiry into the problems of plant growth and development are reviewed with the emphasis on the input of his research in elucidating the mechanisms of flowering, tuberization, sex expression, and the integrity of plant organism. The pioneer studies conducted by Chailakhyan and his colleagues on agricultural applications of phytohormones, their synthetic analogs, and other growth regulators are considered. Highlighted is the role of theoretical papers written by Chailakhyan, his lectures, and his brave fight against pseudoscientific trends in the Russian science is stressed.     

Speaking out about the social implications of science: the uneven legacy of H. J. Muller

H. J. Muller (1890-1967) was unusual as a scientist because he spoke out on numerous occasions about the uses and abuses of genetics in society. In this article, I follow Muller's efforts to do so and the consequences that they had on his career, his productivity as a research scientist, and his reputation. The shifting sites of Muller's work--which ranged from Columbia University to Texas, from Berlin to Moscow and Leningrad, from Madrid to Edinburgh, and from Amherst to Indiana University--made his activism unusual. Muller paid a price for his activism, and his reputation today is still marred by what most historians would consider risky judgments and reversals of position about genetics and society. My analysis is not a defense but rather an evaluation of the circumstances that led him to these positions and an analysis of the consequences of challenging society when scientists believe their science is being ignored or abused.     

History of ichnology

William Buckland not only was an eccentric scientist either liked or disliked by his peers but, in the early 1800s, was also the foremost authority on coprolites. The latter were a source of considerable amusement to some of his friends.     

The interface of natural theology and science in the ethology of W. H. Thorpe

Conclusion It should be clear by now the extent to which many features of Thorpe's interpretation of animal behavior and of the animal mind rested, at bottom, not simply on conventional scientific proofs but on interpretive inferences, which in turn rested on a willingress to make extensions of human experience to animals. This, in turn, rested on his view of evolution and his view of reality. And these were governed by his natural theology, which was the fundamental stratum of his intellectual experience.Contrary to the scientific ethos, which restricts theory choice to scientific issues alone, Thorpe's career suggests that the actual reasons for theory choice among scientists often are not limited to science, but are multiple and may sometimes be difficult to discover. It is largely because Thorpe took a public part in the natural theology enterprise that we can know something about his religious beliefs and so can see their probable influence on his scientific decisions. Similar beliefs of other scientists are sometimes harder to get at. Most may be practically beyond discovery, for the ethos of science has discouraged public professions of personal belief in relation to scientific work.¹⁰¹ Yet does it seem plausible that, for example, the restriction of self-consciousness to humans by some scientists is a purely scientific decision?¹⁰² Surely not, any more than that the strong influence of natural theology on Thorpe's thought means that he was not a good scientist. His natural theology may have led him into incautious enthusiasms regarding the animal mind — such as the potential if unrealizable linguistic ability of chimpanzees — through a bias in favor of the continuity of emergents in a progressive evolutionary system, just as it led him to advocate animal consciousness long before the recent upsurge of interest, but the scientific integrity of his work overall is unimpeachable. And yet, that work is not comprehensible historically as science alone. Personal philosophy must not be discounted in writing the history of recent science. This somewhat obvious conclusion (obvious to historians of science) needs emphasis, for we are still prone to think that the sciences of our own time provide their own internal dynamic that is in itself sufficient to account for their content and development.     

Boris Balinsky: transition from embryology to developmental biology

This is the story of a textbook that students of developmental biology have used for 45 years. "An Introduction to Embryology" was released soon after a role for genes in the control of development became finally recognized but not yet well documented. Thus this book manifested the transition from embryology to developmental biology. The story of its author, Boris Balinsky, who against all odds survived to write this book, is remarkable on its own. He started his scientific career in the USSR, but due to 20th century social and political upheavals, ended it in South Africa. This article will shed light on the life of Boris Balinsky, a scientist and writer and will explore the origins of his book.     

The Proverbial Bourdieu: Habitus and the Politics of Representation in the Ethnography of Kabylia

Since the 1970s, anthropologists have been centrally concerned with the relationship of ethnographic representation to political and historical context. Interestingly, the work of Pierre Bourdieu has largely escaped such contextualization, despite the significance of Bourdieu's ideas to anthropological theorizing. Today, many of Bourdieu's central concepts float free from the context out of which they arose—the Kabyle region of Algeria. This article addresses this omission by reading Bourdieu's early works against each other to reconstitute aspects of his methodology and fieldwork. Focusing on his choice to represent the Kabyles of his early work in prose, and those in his later work via proverbs, I suggest that key premises of Bourdieu's theory may not be supported by historical and ethnographic evidence. I consider how Bourdieu's position as a young social scientist grappling with ethnographic responsibilities in colonial wartime led him to privilege his interlocutors' accounts in some studies while expunging them from others. [Keywords: Bourdieu, represented speech, literacy, Algeria, Berbers]     

Marvelling at the Marvel: The Supposed Conversion of A.D. Darbishire to Mendelism

The so-called “biometric-Mendelian controversy” has received much attention from science studies scholars. This paper focuses on one scientist involved in this debate, Arthur Dukinfield Darbishire, who performed a series of hybridization experiments with mice beginning in 1901. Previous historical work on Darbishire’s experiments and his later attempt to reconcile Mendelian and biometric views describe Darbishire as eventually being “converted”' to Mendelism. I provide a new analysis of this episode in the context of Darbishire’s experimental results, his underlying epistemology, and his influence on the broader debate surrounding the rediscovery and acceptance of Mendelism. Iinvestigate various historiographical issues raised by this episode in order to reflect on the idea of “conversion” to a scientific theory. Darbishire was an influential figure who resisted strong forces compelling him to convert prematurely due to his requirements that the new theory account for particularly important anomalous facts and answer the most pressing questions in the field. This revised version was published online in July 2006 with corrections to the Cover Date.     

The history of the Purine Club: a tribute to Prof. Geoffrey Burnstock

The international purinergic scientific community has lost its pioneer. Geoffrey Burnstock, born on the 10th of May 1929 in London, died on the 2nd of June 2020, aged 91, in Melbourne (Australia). Geoff was one of the most highly regarded scientists of his generation. In the 1960s and 1970s, he developed a radical and somehow heretical new theory and opened an entire new field of science, signalling via extracellular nucleotides (the “purinergic theory”), which revolutionized our understanding of how cells communicate between each other. Initially, his unconventional theory found a lot of resistance in the scientific community. Once, one scientist even threatened to devote his entire life to disproving Burnstock’s theory. Undeterred, Geoff went further on, and continued to accumulate evidence in favour of his hypothesis, and led the field ever since. He struggled to attract new scientists to this new field of research and, in the early 1990s, due to new molecular biology techniques making it possible to isolate and identify cell surface receptors for ATP and its breakdown product adenosine, did evidence emerge that eventually convinced the doubters. The number of spontaneous obituaries and messages honouring Geoff’s memory that have appeared on specialized Journals and in the public press throughout the world since last June indicates that many people are clearly affected by his death. Besides being a rigorous, ethical and extremely brilliant scientist, Geoff was an extraordinary human being, always eager to collaborate and share data, never jealous of his findings and capable of learning things even from young people. He was known for his enthusiasm, empathy and ability to motivate young scientists and promote their careers. After the establishment of the Purine Club back in the 1990s, numerous Purine Club Chapters have been formed around the world with Geoff’s help and encouragement. He has obviously also been the inspirator and founder of our Journal, Purinergic Signalling (PUSI). For this reason, Charles Kennedy, the current Editor of the Journal, and myself thought that it might be nice to invite representatives from all known Purine Clubs to send a few notes to be published in PUSI on the history of their club and how Geoff inspired, aided or supported them. Here, I have collected all their contributions and I share with the entire purinergic community my personal memories on how the Purine Club was born and developed thanks to the invaluable mentoring of Geoffrey Burnstock. I apologize in advance if I am missing some information or forgot to mention somebody, and I strongly encourage all readers to submit memories and additional information that I shall gather for future writing. Keeping alive the history of how the field developed will be the best tribute that we can play to celebrate Geoff’s work along the years.

     

The Use and Abuse of Sir Karl Popper

Karl Popper has been one of the few philosophers of sciences who has influenced scientists. I evaluate Popper's influence on our understanding of evolutionary theory from his earliest publications to the present. Popper concluded that three sorts of statements in evolutionary biology are not genuine laws of nature. I take him to be right on this score. Popper's later distinction between evolutionary theory as a metaphysical research program and as a scientific theory led more than one scientist to misunderstand his position on evolutionary theory as a scientific theory. In his later work Popper also introduced what he took to be improvements of evolutionary theory. Thus far these improvements have had almost no influence on evolutionary biology. I conclude by examining the influence of Popper on the reception of cladistic analysis.     

Control of water-use efficiency by florigen

A major issue in modern agriculture is water loss through stomata during photosynthetic carbon assimilation. In water-limited ecosystems, annual plants have strategies to synchronize their growth and reproduction to the availability of water. Some species or ecotypes of flowers are early to ensure that their life cycles are completed before the onset of late season terminal drought (“drought escape”). This accelerated flowering correlates with low water-use efficiency (WUE). The molecular players and physiological mechanisms involved in this coordination are not fully understood. We analyzed WUE using gravimetry, gas exchange, and carbon isotope discrimination in florigen deficient (sft mutant), wild-type (Micro-Tom), and florigen over-expressing (SFT-ox) tomato lines. Increased florigen expression led to accelerated flowering time and reduced WUE. The low WUE of SFT-ox was driven by higher stomatal conductance and thinner leaf blades. This florigen-driven effect on WUE appears be independent of abscisic acid (ABA). Our results open a new avenue to increase WUE in crops in an ABA-independent manner. Manipulation of florigen levels could allow us to produce crops with a life cycle synchronized to water availability.     

The Gentleman and the Rogue: The Collaboration Between Charles Darwin and Carl Vogt

This paper investigates the relationship between the eminent 19th-century naturalists Charles Darwin and Carl Vogt. On two separate occasions, Vogt asked Darwin for permission to translate some of the latter’s books into German, and in both cases Darwin refused. It has generally been assumed that Darwin turned down Vogt as a translator because of the latter’s reputation as a radical libertine who was extremely outspoken in his defence of scientific materialism and atheism. However, this explanation does not fit the facts, since, on closer investigation, Darwin not only gave serious consideration to engaging Vogt as the German translator of two of his books, albeit ultimately rejecting him, but he also collaborated with Vogt on the French editions of his works. In this paper we argue that this was not because Darwin was unaware of Vogt’s personality and blunt writing style; rather, Darwin seems to have decided that the benefits he would gain from their association would clearly outweigh the risk of offending some of his readers: in working with Vogt, who was not only a knowledgeable scientist but also an avowed adherent of Darwinism, Darwin could be assured of the scientific quality of the translation and of an edition that would not distort his central concepts – both of which were by no means matters of course in 19th-century translations of scientific works.     

Florigen （Ⅱ）： It is a Mobile Protein

The true identity of florigen - the molecule（s） that migrates from leaves to apical meristem to initiate flowering - was notoriously elusive, having made it almost the ＂Bigfoot＂ of plant biology. There was never a lack of drama in the field of florigen study, and florigen researchers have once again experienced such a swing in the last two years. We wrote a minireview last year in this journal （Yu et al. 2006） to excitedly salute, among other discoveries, the notion that the flowering locus T （FT） mRNA might be the molecular form of a florigen. However, this hypothesis was challenged in a little less than two years after its initial proposition, and the original paper proposed that the FT mRNA hypothesis was retracted （Huang et al. 2005; Bohlenius et al. 2007）. Interestingly enough, the FT gene previously proposed to encode a florigen was never challenged. Rather, the FT protein, instead of the FT mRNA, is now believed to migrate from leaves to the apical meristem to promote floral initiation. In this update, we will share with our readers some entertaining stories concerning the recent studies of florigen in five different plant species. In addition to the published reports referenced inthis update, readers may also refer to our previous minireview and references therein for additional background information （Yu et al. 2006）.     

The reactions on Hugo de Vries's Intracellular pangenesis: the discussion with August Weismann

In 1889 Hugo de Vries published Intracellular Pangenesis in which heformulated his ideas on heredity. The highexpectations of the impression these ideaswould make did not come true and publicationwas negated or reviewed critically. From thereactions of his Dutch colleagues and thediscussion with the famous German zoologistAugust Weismann we conclude that the assertionthat each cell contains all hereditary materialwas controversial and even more the claim thatcharacters are inherited independently of eachother. De Vries felt that he had to convincehis colleagues of the validity of his theory byproviding experimental evidence. He establishedan important research program which resulted inthe rediscovery of Mendel's laws and thepublication of The Mutation Theory.This article also illustrates somephenomena that go beyond an interesting episodein the development of theories of heredity. Itshows that criticism from colleagues can move aresearcher so deeply that he feels compelled toset up an extensive research program. Moreoverit illustrates that it is not unusual that acreative scientist is only partially willing totake criticism on his theories into account.Last but not least it demonstrates that commonopinion on the validity of specific argumentsmay change in the course of time.     

ZCN8 encodes a potential orthologue of Arabidopsis FT florigen that integrates both endogenous and photoperiod flowering signals in maize

Higher plants use multiple perceptive measures to coordinate flowering time with environmental and endogenous cues. Physiological studies show that florigen is a mobile factor that transmits floral inductive signals from the leaf to the shoot apex. Arabidopsis FT protein is widely regarded as the archetype florigen found in diverse plant species, particularly in plants that use inductive photoperiods to flower. Recently, a large family of FT homologues in maize, the Zea CENTRORADIALIS (ZCN) genes, was described, suggesting that maize also contains FT-related proteins that act as a florigen. The product of one member of this large family, ZCN8, has several attributes that make it a good candidate as a maize florigen. Mechanisms underlying the floral transition in maize are less well understood than those of other species, partly because flowering in temperate maize is dependent largely on endogenous signals. The maize indeterminate1 (id1) gene is an important regulator of maize autonomous flowering that acts in leaves to mediate the transmission or production of florigenic signals. This study finds that id1 acts upstream of ZCN8 to control its expression, suggesting a possible new link to flowering in day-neutral maize. Moreover, in teosinte, a tropical progenitor of maize that requires short-day photoperiods to induce flowering, ZCN8 is highly up-regulated in leaves under inductive photoperiods. Finally, vascular-specific expression of ZCN8 in Arabidopsis complements the ft-1 mutation, demonstrating that leaf-specific expression of ZCN8 can induce flowering. These results suggest that ZCN8 may encode a florigen that integrates both endogenous and environmental signals in maize.