Evolution of the bilaterian germ line: lineage origin and modulation of specification mechanisms

A key focus of evolutionary developmental biology (evo–devo)in recent years has been to elucidate the evolution of developmentalmechanisms as a means of reconstructing the hypothetical lastcommon ancestors of various clades. Prominent among such reconstructionshave been proposals as to the nature of the mysterious "Urbilateria,"originally defined as the last common ancestor of the extantBilateria (protostomes and deuterostomes). Indeed, drawingsof this animal can now be found, as well as detailed informationon the genetics and morphological processes that it used toconstruct its gut, heart, eyes, appendages, segments, and bodyregions. Perhaps surprisingly, however, no explanations haveyet been offered as to how this animal might have achieved thesuccessful reproduction that must have been necessary for itto give rise to those lineages that are ancestral to today'sdiverse clades. The present article examines the comparativedata available to date on the specification of the only cellscontaining the genetic hereditary material, the germ cells,and speculates on the possible evolutionary and developmentalorigin of the Urbilaterian germ line.     

A Closer Look at Amphetamine-Induced Reverse Transport and Trafficking of the Dopamine and Norepinephrine Transporters

Amphetamine (AMPH) and its derivatives are regularly used in the treatment of a wide array of disorders such as attention-deficit hyperactivity disorder (ADHD), obesity, traumatic brain injury, and narcolepsy (Prog Neurobiol 75:406–433, 2005; J Am Med Assoc 105:2051–2054, 1935; J Am Acad Child Adolesc Psychiatry 41:514–521, 2002; Neuron 43:261–269, 2004; Annu Rev Pharmacol Toxicol 47:681–698, 2007; Drugs Aging 21:67–79, 2004). Despite the important medicinal role for AMPH, it is more widely known for its psychostimulant and addictive properties as a drug of abuse. The primary molecular targets of AMPH are both the vesicular monoamine transporters (VMATs) and plasma membrane monoamine—dopamine (DA), norepinephrine (NE), and serotonin (5-HT)—transporters. The rewarding and addicting properties of AMPH rely on its ability to act as a substrate for these transporters and ultimately increase extracellular levels of monoamines. AMPH achieves this elevation in extracellular levels of neurotransmitter by inducing synaptic vesicle depletion, which increases intracellular monoamine levels, and also by promoting reverse transport (efflux) through plasma membrane monoamine transporters (J Biol Chem 237:2311–2317, 1962; Med Exp Int J Exp Med 6:47–53, 1962; Neuron 19:1271–1283, 1997; J Physiol 144:314–336, 1958; J Neurosci 18:1979–1986, 1998; Science 237:1219–1223, 1987; J Neurosc 15:4102–4108, 1995). This review will focus on two important aspects of AMPH-induced regulation of the plasma membrane monoamine transporters—transporter mediated monoamine efflux and transporter trafficking.     

The NMR restraints grid at BMRB for 5,266 protein and nucleic acid PDB entries

Several pilot experiments have indicated that improvements in older NMR structures can be expected by applying modern software and new protocols (Nabuurs et al. in Proteins 55:483–186, 2004; Nederveen et al. in Proteins 59:662–672, 2005; Saccenti and Rosato in J Biomol NMR 40:251–261, 2008). A recent large scale X-ray study also has shown that modern software can significantly improve the quality of X-ray structures that were deposited more than a few years ago (Joosten et al. in J. Appl Crystallogr 42:376–384, 2009; Sanderson in Nature 459:1038–1039, 2009). Recalculation of three-dimensional coordinates requires that the original experimental data are available and complete, and are semantically and syntactically correct, or are at least correct enough to be reconstructed. For multiple reasons, including a lack of standards, the heterogeneity of the experimental data and the many NMR experiment types, it has not been practical to parse a large proportion of the originally deposited NMR experimental data files related to protein NMR structures. This has made impractical the automatic recalculation, and thus improvement, of the three dimensional coordinates of these structures. We here describe a large-scale international collaborative effort to make all deposited experimental NMR data semantically and syntactically homogeneous, and thus useful for further research. A total of 4,014 out of 5,266 entries were ‘cleaned’ in this process. For 1,387 entries, human intervention was needed. Continuous efforts in automating the parsing of both old, and newly deposited files is steadily decreasing this fraction. The cleaned data files are available from the NMR restraints grid at .     

Phylogenetic Position of <Emphasis Type="Italic">Corchoropsis</Emphasis> Siebold &; Zucc. (Malvaceae s.l.) Inferred from Plastid DNA Sequences

Recent phylogenetic research suggests that Malvaceae s.l. comprises formerly Tiliaceae, Byttneriaceae, Bombacaceae, and Sterculiaceae. Corchoropsis is traditionally included in Tiliaceae or Sterculiaceae and is distributed in China, Korea, and Japan. One to three species have been recognized for this genus. Phylogenetic relationships among the Malvacean taxa have been intensively studied with molecular data, and the evolution of their morphological characteristics has been re-interpreted accordingly. However, no Corchoropsis species have been included for their phylogenetic position. Here, three chloroplast coding regions—rbcL, atpB, and ndhF, from Corchoropsis psilocarpa and Corchoropsis crenata—were amplified and sequenced, then compared with other Malvacean taxa. This analysis of the three plastid gene sequences now places Corchoropsis species in Dombeyoideae, as previously proposed by Takeda (Bull Misc Inform Kew 365, 1912), Tang (Cathaya 4:131–150, 1992), and Bayer and Kubitzki (2003). Within Dombeyoideae, Corchoropsis forms a strongly supported sister relationship with the Dombeya–Ruizia clade.     

Can Internalism and Externalism be Reconciled in a Biological Epistemology of Language?

This paper is an attempt at exploring the possibility of reconciling the two interpretations of biolinguistics which have been recently projected by Koster (Biolinguistics 3(1):61–92, 2009). The two interpretations—trivial and nontrivial—can be roughly construed as non-internalist and internalist conceptions of biolinguistics respectively. The internalist approach boils down to a conception of language where language as a mental grammar in the form of I-language grows and functions like a biological organ. On the other hand, under such a construal consistent with Koster’s (Biolinguistics 3(1):61-92, 2009), the non-internalist version does not necessarily have to be externalist in nature; rather it is a matter of mutual reinforcement of biology and culture under the rubric of a co-evolutionary dynamics. Here it will be argued that the apparent dichotomy between these two conceptions of biolinguistics can perhaps be resolved if we have a richer synthesis that accounts for both internalism and non-internalism.     

Acidithiobacillus thiooxidans secretome containing a newly described lipoprotein Licanantase enhances chalcopyrite bioleaching rate

The nature of the mineral–bacteria interphase where electron and mass transfer processes occur is a key element of the bioleaching processes of sulfide minerals. This interphase is composed of proteins, metabolites, and other compounds embedded in extracellular polymeric substances mainly consisting of sugars and lipids (Gehrke et al., Appl Environ Microbiol 64(7):2743–2747, 1998). On this respect, despite Acidithiobacilli—a ubiquitous bacterial genera in bioleaching processes (Rawlings, Microb Cell Fact 4(1):13, 2005)—has long been recognized as secreting bacteria (Jones and Starkey, J Bacteriol 82:788–789, 1961; Schaeffer and Umbreit, J Bacteriol 85:492–493, 1963), few studies have been carried out in order to clarify the nature and the role of the secreted protein component: the secretome. This work characterizes for the first time the sulfur (meta)secretome of Acidithiobacillus thiooxidans strain DSM 17318 in pure and mixed cultures with Acidithiobacillus ferrooxidans DSM 16786, identifying the major component of these secreted fractions as a single lipoprotein named here as Licanantase. Bioleaching assays with the addition of Licanantase-enriched concentrated secretome fractions show that this newly found lipoprotein as an active protein additive exerts an increasing effect on chalcopyrite bioleaching rate.     

ROS-Mediated ABA Signaling

In plants, reactive oxygen species (ROS) are short-lived molecules produced through various cellular mechanisms in response to biotic and abiotic stimuli. ROS function as second messengers for hormone signaling, development, oxygen deprivation, programmed cell death, and plant–pathogen interactions. Recent research on ROS-mediated responses has produced stimulating findings such as the specific sources of ROS production, molecular elements that work in ROS-mediated signaling and homeostasis, and a ROS-regulated gene network (Neill et al., Curr Opin Plant Biol 5:388–395, 2002a; Apel and Hirt, Annu Rev Plant Biol 55:373–399, 2004; Mittler et al., Trends Plant Sci 9:490–498, 2004; Mori and Schroeder, Plant Physiol 135:702–708, 2004; Kwak et al., Plant Physiol 141:323–329, 2006; Torres et al., Plant Physiol 141:373–378, 2006; Miller et al., Physiol Plant 133:481–489, 2008). In this review, we highlight new discoveries in ROS-mediated abscisic acid (ABA) signaling. Drs. Daeshik Cho and June M. Kwak are the corresponding authors for this paper.     

Simulation of biological evolution under attack,but not really: a response to Meester

The leading Intelligent Design theorist William Dembski (Rowman & Littlefield, Lanham MD, 2002) argued that the first No Free Lunch theorem, first formulated by Wolpert and Macready (IEEE Trans Evol Comput 1: 67–82, 1997), renders Darwinian evolution impossible. In response, Dembski’s critics pointed out that the theorem is irrelevant to biological evolution. Meester (Biol Phil 24: 461–472, 2009) agrees with this conclusion, but still thinks that the theorem does apply to simulations of evolutionary processes. According to Meester, the theorem shows that simulations of Darwinian evolution, as these are typically set in advance by the programmer, are teleological and therefore non-Darwinian. Therefore, Meester argues, they are useless in showing how complex adaptations arise in the universe. Meester uses the term “teleological” inconsistently, however, and we argue that, no matter how we interpret the term, a Darwinian algorithm does not become non-Darwinian by simulation. We show that the NFL theorem is entirely irrelevant to this argument, and conclude that it does not pose a threat to the relevance of simulations of biological evolution.     

A role for anions in ATP synthesis and its molecular mechanistic interpretation

ATP, the ‘universal biological energy currency’, is synthesized by utilizing energy either from oxidation of fuels or from light, via the process of oxidative and photo-phosphorylation respectively. The process is mediated by the enzyme F₁F₀-ATP synthase, using the free energy of ion gradients in the final energy catalyzing step, i.e., the synthesis of ATP from ADP and inorganic phosphate (P_i). The details of the molecular mechanism of ATP synthesis are among the most important fundamental issues in biology and hence need to be properly understood. In this work, a role for anions in making ATP has been found. New experimental data has been reported on the inhibition of ATP synthesis at nanomolar concentrations by the potent, specific anion channel blockers 4,4′-diisothiocyanostilbene-2, 2′-disulphonic acid (DIDS) and tributyltin chloride (TBTCl). Based on these inhibition studies, attention has been drawn to anion translocation (in addition to proton translocation) as a requirement for ATP synthesis. The type of inhibition has been quantified and an overall kinetic scheme for mixed inhibition that explains the data has been evolved. The experimental data and the type of inhibition found have been interpreted in the light of the torsional mechanism of energy transduction and ATP synthesis (Nath J Bioenerg Biomembr 42:293–300, 2010a; J Bioenerg Biomembr 42:301–309, 2010b). This detailed and unified mechanism resolves long-standing problems and inconsistencies in the first theories (Slater Nature 172:975–978, 1953; Williams J Theor Biol 1:1–17, 1961; Mitchell Nature 191:144–148, 1961; Mitchell Biol Rev 41:445–502, 1966), makes several novel predictions that are experimentally verifiable (Nath Biophys J 90:8–21, 2006a; Process Biochem 41:2218–2235, 2006b), and provides us with a new and fruitful paradigm in bioenergetics. The interpretation presented here provides intelligent answers to the unexplained existing results in the literature. It is shown that mechanistic interpretation of the experimental data requires substantial addition to available conceptual foundations such that present concepts, theories, and mechanisms must be revised.     

A Comparative Analysis of Integration Indices

The degree of integration of multidimensional phenotypes has an important place in evolutionary biology, pertaining to the structure of variation that is available for natural selection to work on and therefore to the evolutionary potential of the phenotype. Various indices have been suggested in the literature for measuring integration level, yet their statistical properties have remained mostly unstudied to date. In this study, I used simulations and resampling procedures in order to compare the distributions and sampling properties of different indices. I simulated heterogeneous correlation matrices that ranged widely in their integration level. I applied non-parametric bootstrapping to explore the effect of sampling on recovering the true integration value of these matrices. In addition, I generated the statistical power space for one of the integration indices—the relative standard deviation of the eigenvalues. The results show that the relative variance of eigenvalues maps exactly onto the mean coefficient of determination, and that the index suggested by Hansen and Houle (J Evol Biol 21:1201–1219, 2008) is the same as Van Valen’s (J Theor Biol 45:235–247, 1974) redundancy index, both of which have some undesirable sampling properties that render them less useful in most practical situations. Based on the power analysis, a sample of 30–40 specimens can be considered a sufficient minimum for most studies. The R codes provided here can be utilized by other researchers to yield case-specific insights.     

An alien approach to invasive species: objectivity and society in invasion biology

Several authors have recently argued that invasion biologists should adopt a more objective and dispassionate stance towards invasive species. Brown and Sax (Austral Ecol 29:530–536, 2004; Austral Ecol 30:481–483, 2005) assert that invasion biologists risk their objectivity, “commit the naturalist fallacy” or “embark on a slippery slope” with engaged concern about invasive species. Elsewhere, Colautti and MacIsaac (Divers Distrib 10:135–141, 2004) propose a neutral language for invasion biology, one that insulates scientific from popular discussion about invasive species. While there is certainly hyperbole about the effects of some invasive species, the type of objectivity promoted in these papers may often be inappropriate for invasion biology. It implies a policy of non-action that is inconsistent with the conservation values of many invasion biologists. To engage these values, invasion biologists can adopt deliberative methods for environmental problem-solving that involve stakeholders in their research design and which still promote high standards of scientific rigor.     

An ecological classification of Central European macromoths: habitat associations and conservation status returned from life history attributes

To be used as a predictive conservation tool, classification of animal habitats should rely on actual resource requirements of individual species. Shreeve et al. (J Insect Conserv 5:145–161, 2001) produced a resource-based habitat classification for British butterflies, obtaining habitat association groups, whose constituent species differed in their distribution extent, distribution change and vulnerability in Britain. To test the utility of this approach for a group with a less-known biology, we produced a resource-based classification of habitats of Central European macromoths. We worked with macrolepidopteran moth families, except for the megadiverse Geometridae and Noctuidae. We produced a matrix of 178 life history attributes describing resource use by 164 species, subjected the matrix to ordination analysis, and compared the resulting moths groupings with external ecological information. Five habitat association groups were distinguished: I—close canopy moths, II—open canopy moths, III—grasslands moths, IV—herb-feeding hawk moths, and V—lichen feeders. The classification sustained deleting attributes related to host plants taxonomy. Groups I–III sustained control for taxonomic positions of the moths, whereas IV and V did not. Members of the groups differed in the representation of externally obtained habitat associations, biogeography elements, threat status, and range size. Endangered species were over-represented in groups II and III and underrepresented in group I, in agreement with recent land cover changes across the continent. Species resources can be used to reconstruct their habitat needs, and it is possible to scale up from life histories through habitat use to range structures.     

On the Theory of Evolution Versus the Concept of Evolution: Three Observations

Here we address three misconceptions stated by Rice et al. in their observations of our article Paz-y-Mi?o and Espinosa (Evo Edu Outreach 2:655–675, 2009), published in this journal. The five authors titled their note “The Theory of Evolution is Not an Explanation for the Origin of Life.” First, we argue that it is fallacious to believe that because the formulation of the theory of evolution, as conceived in the 1800s, did not include an explanation for the origin of life, nor of the universe, the concept of evolution would not allow us to hypothesize the possible beginnings of life and its connections to the cosmos. Not only Stanley Miller’s experiments of 1953 led scientists to envision a continuum from the inorganic world to the origin and diversification of life, but also Darwin’s own writings of 1871. Second, to dismiss the notion of Rice et al. that evolution does not provide explanations concerning the universe or the cosmos, we identify compelling scientific discussions on the topics: Zaikowski et al. (Evo Edu Outreach 1:65–73, 2008), Krauss (Evo Edu Outreach 3:193–197, 2010), Peretó et al. (Orig Life Evol Biosph 39:395–406, 2009) and Follmann and Brownson (Naturwissenschaften 96:1265–1292, 2009). Third, although we acknowledge that the term Darwinism may not be inclusive of all new discoveries in evolution, and also that creationists and Intelligent Designers hijack the term to portray evolution as ideology, we demonstrate that there is no statistical evidence suggesting that the word Darwinism interferes with public acceptance of evolution, nor does the inclusion of the origin of life or the universe within the concept of evolution. We examine the epistemological and empirical distinction between the theory of evolution and the concept of evolution and conclude that, although the distinction is important, it should not compromise scientific logic.     

The Morphostatic Limit for a Model of Skeletal Pattern Formation in the Vertebrate Limb

A recently proposed mathematical model of a “core” set of cellular and molecular interactions present in the developing vertebrate limb was shown to exhibit pattern-forming instabilities and limb skeleton-like patterns under certain restrictive conditions, suggesting that it may authentically represent the underlying embryonic process (Hentschel et al., Proc. R. Soc. B 271, 1713–1722, 2004). The model, an eight-equation system of partial differential equations, incorporates the behavior of mesenchymal cells as “reactors,” both participating in the generation of morphogen patterns and changing their state and position in response to them. The full system, which has smooth solutions that exist globally in time, is nonetheless highly complex and difficult to handle analytically or numerically. According to a recent classification of developmental mechanisms (Salazar-Ciudad et al., Development 130, 2027–2037, 2003), the limb model of Hentschel et al. is “morphodynamic,” since differentiation of new cell types occurs simultaneously with cell rearrangement. This contrasts with “morphostatic” mechanisms, in which cell identity becomes established independently of cell rearrangement. Under the hypothesis that development of some vertebrate limbs employs the core mechanism in a morphostatic fashion, we derive in an analytically rigorous fashion a pair of equations representing the spatiotemporal evolution of the morphogen fields under the assumption that cell differentiation relaxes faster than the evolution of the overall cell density (i.e., the morphostatic limit of the full system). This simple reaction–diffusion system is unique in having been derived analytically from a substantially more complex system involving multiple morphogens, extracellular matrix deposition, haptotaxis, and cell translocation. We identify regions in the parameter space of the reduced system where Turing-type pattern formation is possible, which we refer to as its “Turing space.” Obtained values of the parameters are used in numerical simulations of the reduced system, using a new Galerkin finite element method, in tissue domains with nonstandard geometry. The reduced system exhibits patterns of spots and stripes like those seen in developing limbs, indicating its potential utility in hybrid continuum-discrete stochastic modeling of limb development. Lastly, we discuss the possible role in limb evolution of selection for increasingly morphostatic developmental mechanisms.     

A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems

A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well‐suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism – emphasizing eco evo devo, and identify current gaps in knowledge.     

Rapid increase in viability due to new beneficial mutations in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

It is usually assumed that new beneficial mutations are extremely rare. Yet, few experiments have been performed in multicellular organisms that measure the effect of new beneficial mutations on viability and other measures of fitness. In most experiments, it is difficult to clearly distinguish whether adaptations have occurred due to selection on new beneficial mutations or on preexisting genetic variation. Using a modification of a Dobzhansky and Spassky (Evolution 1:191–216, 1947) assay to study change in viability over generations, we have observed an increase in viability in lines homozygous for the second and third chromosomes of Drosophila melanogaster in 6–26 generations due to the occurrence of new beneficial mutations in population sizes of 20, 100 and 1,000. The lines with the lowest initial viability responded the fastest to new beneficial mutations. These results show that new beneficial mutations, along with selection, can quickly increase viability and fitness even in small populations. Hence, new advantageous mutations may play an important role in adaptive evolution in higher organisms.     

Extending Darwin’s analogy: Bridging differences in concepts of selection between farmers, biologists, and plant breeders

Darwin developed his theory of evolution based on an analogy between artificial selection by breeders of his day and “natural selection.” For Darwin, selection included what biologists came to see as being composed of (1) phenotypic selection of individuals based on phenotypic differences, and, when these are based on heritable genotypic differences, (2) genetic response between generations, which can result in (3) evolution (cumulative directional genetic response over generations). The use of the term “selection” in biology and plant breeding today reflects Darwin’s assumption—phenotypic selection is only biologically significant when it results in evolution. In contrast, research shows that small-scale, traditionally-based farmers select seed as part of an integrated production and consumption system in which selection is often not part of an evolutionary process, but is still useful to farmers. Extending Darwin’s analogy to farmers can facilitate communication between farmers, biologists, and plant breeders to improve selection and crop genetic resource conservation.     

Building momentum for systems and synthetic biology in India

Biological systems are inherently noisy. Predicting the outcome of a perturbation is extremely challenging. Traditional reductionist approach of describing properties of parts, vis-a-vis higher level behaviour has led to enormous understanding of fundamental molecular level biology. This approach typically consists of converting genes into junk (knock-down) and garbage (knock-out) and observe how a system responds. To enable broader understanding of biological dynamics, an integrated computational and experimental strategy was formally proposed in mid 1990s leading to the re-emergence of Systems Biology. However, soon it became clear that natural systems were far more complex than expected. A new strategy to address biological complexity was proposed at MIT (Massachusetts Institute of Technology) in June 2004, when the first meeting of synthetic biology was held. Though the term ‘synthetic biology’ was proposed during 1970s (Szybalski in Control of gene expression, Plenum Press, New York, 1974), the usage of the original concept found an experimental proof in 2000 with the demonstration of a three-gene circuit called repressilator (Elowitz and Leibler in Nature, 403:335–338, 2000). This encouraged people to think of forward engineering biology from a set of well described parts.     

Brocchi,Darwin, and Transmutation: Phylogenetics and Paleontology at the Dawn of Evolutionary Biology

Giambattista Brocchi’s (1814) monograph (see Dominici, Evo Edu Outreach, this issue, 2010) on the Tertiary fossils of the Subappenines in Italy—and their relation to the living molluscan fauna—contains a theoretical, transmutational perspective (“Brocchian transmutation”). Unlike Lamarck (1809), Brocchi saw species as discrete and fundamentally stable entities. Explicitly analogizing the births and deaths of species with those of individual organisms (“Brocchi’s analogy”), Brocchi proposed that species have inherent longevities, eventually dying of old age unless driven to extinction by external forces. As for individuals, births and deaths of species are understood to have natural causes; sequences of births and deaths of species produce genealogical lineages of descent, and faunas become increasingly modernized through time. Brocchi calculated that over 50% of his fossil species are still alive in the modern fauna. Brocchi’s work was reviewed by Horner (1816) in Edinburgh. Brocchi’s influence as a transmutational thinker is clear in Jameson’s (1827) “geological illustrations” in his fifth edition of his translation of Cuvier’s Theory of the Earth (read by his student Charles Darwin) and in the anonymous essays of 1826 and 1827 published in the Edinburgh New Philosophical Journal—which also carried a notice of Brocchi’s death in 1827. The notion that new species replace older, extinct ones—in what today would be called an explicitly phylogenetic context—permeates these essays. Herschel’s (1830) discussion of temporal replacement of species and the modernization of faunas closely mirrors these prior discussions. His book, dedicated to the search for natural causes of natural phenomena, was read by Charles Darwin while a student at Cambridge. Darwin’s work on HMS Beagle was in large measure an exploration of replacement patterns of “allied forms” of endemic species in time and in space. His earliest discussions of transmutation, in his essay February 1835, as well as the Red Notebook and the early pages of Notebook B (the latter two written in 1837 back in England), contain Brocchi’s analogy, including the idea of inherent species longevities. Darwin’s first theory of the origin of species was explicitly saltational, invoking geographic isolation as the main cause of the abrupt appearance of new species. We conclude that Darwin was testing the predicted patterns of both Brocchian and Lamarckian transmutation as early as 1832 at the outset of his work on the Beagle.     

ABA may affect the dormancy in triticale caryopses by inhibition of embryo class I RNases,enzymes involved in P<Subscript>i</Subscript> release

The main objective of this study was to analyze the differences in profiles of RNase activities from triticale embryos (Triticosecale, cv. Ugo) between dormant and non-dormant caryopses and to determine the influence of exogenous abscisic acid (ABA) on the activities of these enzymes. The major RNase from the examined tissue was detected following SDS-PAGE, with substrate-based gel assay, described by Yen and Green (Plant Physiol 97:1487–1493, 1991). The activities of enzymes were characterized according to their pH optima, ion dependence, EDTA sensitivity and DNase activity. In embryos with arrested growth (in a natural way by dormancy or artificially by ABA treatment), the activity of two enzymes—24 and 27 kDa—belonging to class I RNases was completely inhibited, whereas that of two other RNases of this family—23 and 25 kDa—was detectable. However, the activity of the class I ribonucleases (enzymes responsible for cellular P_i release) was very low. Moreover, in contrast with non-dormant caryopses, imbibing embryos of dormant or ABA-treated seeds contained 13- and 14-kDa enzymes. These enzymes have not been classified so far, and their specific properties are different from the generally accepted properties of ribonucleolytic enzymes. In addition to the above results, the P_i content in the analyzed samples was determined by the Ames (Methods Enzymol 8:115–118, 1966) method. The results suggest a very low and constant level of inorganic phosphate in dormant samples as well as an evidently decreasing P_i content in embryos under the influence of ABA treatment. The inhibition of the class I RNases activity induced by abscisic acid implies that one of the roles of ABA in seed dormancy may consist in arresting the catabolic release of P_i, which results in retarding the embryo’s growth.