Organismal view of a plant and a plant cell.

Cell walls are at the basis of a structural, four-dimensional framework of plant form and growth time. Recent rapid progress of cell wall research has led to the situation where the old, long-lasting juxtaposition: "living" protoplast--"dead" cell wall, had to be dropped. Various attempts of re-interpretation cast, however, some doubts over the very nature of plant cell and the status of the walls within such a cell. Following a comparison of exocellular matrices of plants and animals, their position in relation to cells and organisms is analysed. A multitude of perspectives of the biological organisation of living beings is presented with particular attention paid to the cellular and organismal theories. Basic tenets and resulting corollaries of both theories are compared, and evolutionary and developmental implications are considered. Based on these data, "The Plant Body"--an organismal concept of plants and plant cells is described.     

How many processes are responsible for phenotypic evolution?

SUMMARY In addressing phenotypic evolution, this article reconsiders natural selection, random drift, developmental constraints, and internal selection in the new extended context of evolutionary developmental biology. The change of perspective from the "evolution of phenotypes" toward an "evolution of ontogenies" (evo-devo perspective) affects the reciprocal relationships among these different processes. Random drift and natural selection are sibling processes: two forms of post-productional sorting among alternative developmental trajectories, the former random, the latter nonrandom. Developmental constraint is a compound concept; it contains even some forms of natural ("external" and "internal") selection. A narrower definition ("reproductive constraints") is proposed. Internal selection is not a selection caused by an internal agent. It is a form of environment-independent selection depending on the level of the organism's internal developmental or functional coordination. Selection and constraints are the main deterministic processes in phenotypic evolution but they are not opposing forces. Indeed, they are continuously interacting processes of evolutionary change, but with different roles that should not be confused.     

Dermal and intestinal epithelium of the Enteropneusta as a phylogenetic stage of development of the Chordata

A comparative histological investigation of dermal and intestinal epithelium was made in Saccoglossus mereschkowskii (Enteropneusta). Nucleic acids (Feulgen reaction), glycogen (PAS-reaction, Best's staining), mucous (mucicarmine), total proteins (xanthoprotein reaction), neutral mucopolisaccharides (PAS-reaction) were determined histochemically. The dermal and infestinal epithelia of S. mereschkowskii have false pseudostratified composition and consist of ciliary and glandular cells. Peculiar "giant" cells with phagocytosis as their main function are also found in the intestinal epithelium. Ciliary cells of the intestinal epithelium are capable for secreting. A comparison between the dermal and intestinal epithelii is presented in the article. A supposition is made on the primitive structure of false pseudostratified composition of the dermal and intestinal epithelii. The epithelia of Enteropneusta are considered as an initial developmental stage of dermal and intestinal epithelia in phylogenic line of Hemichodata-Chordata.     

DEVELOPMENTAL QUANTITATIVE GENETICS AND THE EVOLUTION OF ONTOGENIES

A model is presented which permits integration of developmental information into genetic discussions about evolutionary change in morphology. Development of a trait is described in terms of an ontogenetic trajectory whose properties are defined by a small number of parameters. Some evolutionary aspects of development are examined from the perspective of this quantitative genetic model. Particular attention is given to the developmental origin of pleiotropic effects, developmental constraints, heterochrony, and the growth and morphogenesis of complex morphologies. The role of genetic maternal effects in mammalian development is briefly examined, particularly as it relates to selection on developmental traits.     

An analysis of the Caenorhabditis elegans lipid raft proteome using geLC-MS/MS

Lipid rafts are microdomains of the phospholipid bilayer, proposed to form semi-stable "islands" that act as a platform for several important cellular processes; major classes of raft-resident proteins include signalling proteins and glycosylphosphatidylinositol (GPI)-anchored proteins. Proteomic studies into lipid rafts have been mainly carried out in mammalian cell lines and single cell organisms. The nematode Caenorhabditis elegans, the model organism with a well-defined developmental profile, is ideally suited for the study of this subcellular locale in a complex developmental context. A study of the lipid raft proteome of C. elegans is presented here. A total of 44 proteins were identified from the lipid raft fraction using geLC-MS/MS, of which 40 have been determined to be likely raft proteins after analysis of predicted functions. Prediction of GPI-anchoring of the proteins found 21 to be potentially modified in this way, two of which were experimentally confirmed to be GPI-anchored. This work is the first reported study of the lipid raft proteome in C. elegans. The results show that raft proteins, including numerous GPI-anchored proteins, may have a variety of potentially important roles within the nematode, and will hopefully lead to C. elegans becoming a useful model for the study of lipid rafts.     

Development of schematic face preference in macaque monkeys

This study investigated schematic face preferences in infant macaque monkeys. We also examined the roles of whole and partial features in facial recognition and related developmental change. Sixteen infant monkeys, all less than two months old, were presented with two stimulus pairs. Pair A consisted of "face" and "parts," with the components representing facial parts (i.e. eyes, mouth, and nose). Pair B consisted of "configuration" and "linear," each including three black squares. In each pair, one of two stimuli represented a facial configuration, namely "face" and "configuration." Visual following responses toward each stimulus were analyzed. The results revealed an early preference for schematic faces in these nonhuman primates. Infants less than one month of age showed a preference only for a stimulus that contained only whole facial configuration (i.e. "configuration" in Pair B). One-month-old macaque infants showed a preference only for "face" but not for "configuration." This result means that their preference at that age was affected by both the shape of the components and the overall configuration. As the developmental change and the contribution of both facial features are similar to those in human infants, it may suggest that primates share common cognitive processes in early schematic face recognition.     

Feeding behaviour, sensory physiology and nutrient feedback: a unifying model

The design features of gustatory systems are considered in relation to the need for insect herbivores (or indeed any animal) to regulate their nutrient intake. The gustatory system (defined to include both peripheral and central components) should ideally be designed to reflect: (a) the average nutritional requirements of the insect during its various developmental stages; (b) the predictably unpredictable variation in nutrient supply-demand which occurs about that average; and (c) the distribution and composition of foods available in the environment. A mathematical model is presented which makes detailed predictions regarding behavioural and electrophysiological responses to foods or simple solutions varying in nutrient content.     

Amphioxus: how to become a vertebrate

Evo-devo is a young disciplin, which aims to explain the morphological evolution of organisms through developmental mechanisms and genes networks. A major question within this discipline is the origin of vertebrates. It seems now admitted that vertebrates derive from an invertebrate chordate ancestor. Several models among living chordate representatives are used today to answer this question. The small world of evo-evo interested in the emergence of vertebrates is ebullient about the advent of several totally sequenced genomes allowing comparative analyses to become evermore reliable. Furthermore "non classical" models are developed which can be submitted to refined developmental analysis. One of these is amphioxus (genus Branchyostoma), "a peaceful anchory fillet to illuminate chordate evolution" (Garcia-Fernandez, 2006a, b). The features of this model are described in this review.     

Type of rheoreaction in the early ontogenesis of roach <Emphasis Type="Italic">Rutilus rutilus</Emphasis> (L.) as a factor determining its biotopic distribution

The specific features of rheoreaction in roach Rutilus rutilus (L.) larvae from open and protected shallows of the Rybinsk Reservoir have been studied. Data on length and weight of roach sampled at various habitats at B–E developmental stages are presented. It has been revealed that the type of roach larvae rheoreaction is a behavioral mechanism of their distribution over different types of habitats, not only in rivers but also in the waterbodies with slow water turnover rates—lakes and reservoirs. By the time of developmental stage E, this mechanism provides the sustainable spatial separation of juvenile fish, which in the future may lead to intrapopulation differentiation in roach.     

The establishment of vascular-derived microenvironments in the developing chick wing

The results of previous studies on the temporal sequence of limb vascularization suggest that the prospective myogenic and chondrogenic areas of the mesoderm are distinguished by a differential vascularization pattern prior to the overt expression of muscle- and cartilage-specific phenotypes. The experiments presented here are designed to reveal the dynamic aspects of vascular flow in the limb by the observation of how an inert, particular tracer (india ink) is mobilized and dispersed at specific points in the mesoderm. Data are presented as a temporal sequence of fluid flow "maps" which detail both the rate and the direction of vascular flow in the limb. It is proposed that not only does the vasculature compartmentalize the mesoderm into prospective myogenic and chondrogenic zones but also that these broad areas are subcompartmentalized into discrete microenvironments that are spatially distinct with regard to their capacity for transporting the carbon particles. The developmental significance of this observation may be that limb mesodermal cells are granted precise, "positional" information in the form of the specific nutrient and oxygen levels they encounter during critical, or decisional, phases of morphogenesis.     

Structure and functions of arthropod proteasomes

Recent work on structural/functional relationships in arthropod proteasomes is reviewed. Taking advantage of our ability to induce a stable, proteolytically-active conformation of the lobster proteasome, the structures of basal and heat-activated complexes were probed with exogenous proteases. Increased sensitivity to chymotrypsin and trypsin showed that heat activation induced a more open conformation, allowing entry of large substrates into the catalytic chamber. In Drosophila, the effects of two developmental mutant alleles (DTS-7 and DTS-5) encoding proteasome subunits (Z and C5, respectively) on the subunit composition and catalytic activities of the enzyme were examined. Both qualitative and quantitative differences in compositions between wild-type (+/+) and heterozygotes (+/DTS) indicated that incorporation of mutant subunits alters post-translational modifications of the complex. Catalytic activities, however, were similar, which suggests that the developmental defect involves other proteasome properties, such as intracellular localization and/or interactions with endogenous regulators. A hypothetical model in which DTS subunits act as poison subunits is presented.     

Long-term effects of the perinatal environment on respiratory control.

The respiratory control system exhibits considerable plasticity, similar to other regions of the nervous system. Plasticity is a persistent change in system behavior triggered by experiences such as changes in neural activity, hypoxia, and/or disease/injury. Although plasticity is observed in animals of all ages, some forms of plasticity appear to be unique to development (i.e., "developmental plasticity"). Developmental plasticity is an alteration in respiratory control induced by experiences during "critical" developmental periods; similar experiences outside the critical period will have little or no lasting effect. Thus complementary experiments on both mature and developing animals are generally needed to verify that the observed plasticity is unique to development. Frequently studied models of developmental plasticity in respiratory control include developmental manipulations of respiratory gas concentrations (O(2) and CO(2)). Environmental factors not specifically associated with breathing may also trigger developmental plasticity, however, including psychological stress or chemicals associated with maternal habits (e.g., nicotine, cocaine). Despite rapid advances in describing models of developmental plasticity in breathing, our understanding of fundamental mechanisms giving rise to such plasticity is poor; mechanistic studies of developmental plasticity are of considerable importance. Developmental plasticity may enable organisms to "fine tune" their phenotype to optimize the performance of this critical homeostatic regulatory system. On the other hand, developmental plasticity could also increase the risk of disease later in life. Future directions for studies concerning the mechanisms and functional implications of developmental plasticity in respiratory motor control are discussed.     

Developmental drive: an important determinant of the direction of phenotypic evolution

SUMMARY Over any period of evolutionary time, the prevailing ontogenetic trajectory within a lineage may either recur unchanged from generation to generation (stasis) or alter (developmental reprogramming). A key question about reprogramming is whether it exhibits intrinsic biases in favor of some sorts of change and against others, which may be referred to respectively as "drive" and "constraint." A simple logical argument suggests that both drive and constraint should be common, and conversely that cases of equiprobable modification in various phenotypic directions should be relatively rare. These proposals, that drive and constraint exist and that they are common, appear to be widely accepted, even among neo-Darwinians, who are sometimes portrayed as rejecting them. What is more controversial is that developmental drive (and constraint) can have a powerful influence on the direction of evolutionary change. It is argued that such an influence will occur, and indeed may be pervasive.     

Identification and functional analysis of a defect in the human ALG9 gene: definition of congenital disorder of glycosylation type IL

Defects of lipid-linked oligosaccharide assembly lead to alterations of N-linked glycosylation known as "type I congenital disorders of glycosylation" (CDG). Dysfunctions along this stepwise assembly pathway are characterized by intracellular accumulation of intermediate lipid-linked oligosaccharides, the detection of which contributes to the identification of underlying enzymatic defects. Using this approach, we have found, in a patient with CDG, a deficiency of the ALG9 alpha 1,2 mannosyltransferase enzyme, which causes an accumulation of lipid-linked-GlcNAc(2)Man(6) and -GlcNAc(2)Man(8) structures, which was paralleled by the transfer of incomplete oligosaccharides precursors to protein. A homozygous point-mutation 1567G-->A (amino acid substitution E523K) was detected in the ALG9 gene. The functional homology between the human ALG9 and Saccharomyces cerevisiae ALG9, as well as the deleterious effect of the E523K mutation detected in the patient with CDG, were confirmed by a yeast complementation assay lacking the ALG9 gene. The ALG9 defect found in the patient with CDG--who presented with developmental delay, hypotonia, seizures, and hepatomegaly--shows that efficient lipid-linked oligosaccharide synthesis is required for proper human development and physiology. The ALG9 defect presented here defines a novel form of CDG named "CDG-IL."