bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the expression patterns of LEAFY/FLORICAULA and NEEDLY orthologs in female and male cones of the conifer genera Picea, Podocarpus, and Taxus: implications for current evo‐devo hypotheses for gymnosperms
Authors: Vázquez‐Lobo Alejandra , Carlsbecker Annelie , Vergara‐Silva Francisco , Alvarez‐Buylla Elena R. , Piñero Daniel , Engström Peter
Published: August 2010

SUMMARY
The identity of genes causally implicated in the development and evolutionary origin of reproductive characters in gymnosperms is largely unknown. Working within the framework of plant evolutionary developmental biology, here we have cloned, sequenced, performed phylogenetic analyses upon and tested the expression patterns of LEAFY/FLORICAULA and NEEDLY orthologs in reproductive structures from selected species of the conifer genera Picea, Podocarpus, and Taxus. Contrary to expectations based on previous assessments, expression of LFY/FLO and NLY in cones of these taxa was found to occur simultaneously in a single reproductive axis, initially overlapping but later in mutually exclusive primordia and/or groups of developing cells in both female and male structures. These observations directly affect the status of the “mostly male theory” for the origin of the angiosperm flower. On the other hand, comparative spatiotemporal patterns of the expression of these genes suggest a complex genetic regulatory network of cone development, as well as a scheme of functional divergence for LFY/FLO with respect to NLY homologs in gymnosperms, both with clear heterochronic aspects. Results presented in this study contribute to the understanding of the molecular‐genetic basis of morphological evolution in conifer cones, and may aid in establishing a foundation for gymnosperm‐specific, testable evo‐devo hypotheses.
Widespread RNA segregation in a spiralian embryo
Authors: Kingsley Evan P. , Chan Xin Yi , Duan Yingli , Lambert J. David
Published: August 2010

SUMMARY
Asymmetric cell divisions are a crucial mode of cell fate specification in multicellular organisms, but their relative contribution to early embryonic patterning varies among taxa. In the embryo of the mollusc Ilyanassa, most of the early cell divisions are overtly asymmetric. During Ilyanassa early cleavage, mRNAs for several conserved developmental patterning genes localize to interphase centrosomes, and then during division they move to a portion of the cortex that will be inherited by one daughter cell. Here we report an unbiased survey of RNA localization in the Ilyanassa embryo, and examine the overall patterns of centrosomal localization during early development. We find that 3–4% of RNAs are specifically localized to centrosomes during early development, and the remainder are either ubiquitously distributed throughout the cytoplasm or weakly enriched on centrosomes compared with levels in the cytoplasm. We observe centrosomal localization of RNAs in all cells from zygote through the fifth cleavage cycle, and asymmetric RNA segregation in all divisions after the four‐cell stage. Remarkably, each specifically localized message is found on centrosomes in a unique subset of cells during early cleavages, and most are found in unique sets of cells at the 24‐cell stage. Several specifically localized RNAs are homologous to developmental regulatory proteins in other embryos. These results demonstrate that the mechanisms of localization and segregation are extraordinarily intricate in this system, and suggest that these events are involved in cell fate specification across all lineages in the early Ilyanassa embryo. We propose that greater reliance on segregation of determinants in early cleavage increases constraint on cleavage patterns in molluscs and other spiralian groups.
Muscular derivatives of the cranialmost somites revealed by long‐term fate mapping in the Mexican axolotl (Ambystoma mexicanum)
Authors: Piekarski Nadine , Olsson Lennart
Published: August 2010

SUMMARY
The fate of single somites has not been analyzed from a comparative perspective with modern cell‐marking methods. Most of what we know is based on work using quail‐chick chimeras. Consequently, to what degree cell fate has been conserved despite the anatomical differences among vertebrates is unknown. We have analyzed the cell fate of the cranialmost somites, with the focus on somite two, in the Mexican axolotl (Ambystoma mexicanum). Somite cells were marked by injection of dextran–fluorescein and detected using immunofluorescence after 2 months of development in paraffin sections. Our data confirm and extend earlier studies based on classical histology in salamanders. We show that somite two contributes to different muscles, skeletal elements, and connective tissues of the head and cranial trunk region. Cells from somites two and three migrate latero‐ventrally and contribute to the hypobranchial muscles mm. geniohyoideus and rectus cervicis. We provide evidence that the specific formation of the hypobranchial musculature from ventral processes of the somites might be variable in different classes of vertebrates. We further demonstrate that mm. cucullaris and dilatator laryngis, which were earlier thought to have a branchial origin, arise from somitic material in a manner very similar to the findings in quail‐chick chimeras. Our findings indicate that the pattern of somitic derivatives is highly conserved within tetrapods.
Reproduction in a carnivorous sponge: the significance of the absence of an aquiferous system to the sponge body plan
Authors: Riesgo Ana , Taylor Chantel , Leys Sally P.
Published: August 2010

SUMMARY
Sponges usually produce, release, and capture gametes via the aquiferous system, and so the absence of both choanocytes and an aquiferous system in the carnivorous sponge Asbestopluma occidentalis has led to unusual characteristics of development for this Phylum. Sperm are highly specialized elongate cells tightly packed into spermatic cysts in the peripheral tissue of the sponge. Mature spermatozoa have proacrosomal vesicles at the anterior end and a ciliary pit surrounding the flagellum. Clusters of four to five oocytes are in synchronous stages of cleavage, suggesting that fertilization is synchronous. All stages of embryos occur in the same individual. Early cleavage was holoblastic and equal; blastomeres in two‐, four‐ and eight‐cell embryos were compact and 16‐cell stage embryos were bi‐layered. Late‐stage embryos show three cellular regions along the anterior‐posterior axis: the anterior hemisphere with heterogeneous cells, a mid‐region with cells lying perpendicular to the A‐P axis in a collagenous matrix, and small cells at the posterior pole. Unusually for Porifera, multiciliated cells cover all but the posterior pole. It is inferred that fertilization occurs by capture of intact spermatic cysts whose surrounding forceps spicules become trapped in the anisochelae of neighboring sponges. The elongate shape of sperm may be designed to penetrate the loose collagenous mesohyl, such that the arrival of a packet of sperm would lead to simultaneous fertilization of oocytes in a cluster. Loss of the water canal system in carnivorous sponges has allowed the evolution of features that are highly specialized for the habitat of this animal, but such modifications were not necessarily a prerequisite for the subsequent evolution of metazoans. Given the extremely versatile mechanisms of gametogenesis, embryogenesis, and tissue/body structure in sponges, generalizations regarding basal metazoan reproduction, development, and structure must be approached with caution.
Intermediate modes of larval development: bridging the gap between planktotrophy and lecithotrophy
Authors: Allen Jonathan D. , Pernet Bruno
Published: August 2010

SUMMARY
The extraordinary diversity of larval form and function in marine invertebrates has motivated many studies of development, ecology, and evolution. Among organisms with pelagic development via a larval stage, this diversity is often reduced to a dichotomy between two broad nutritional categories: planktotrophy and lecithotrophy. Despite the clear utility of the planktotrophy–lecithotrophy dichotomy to those interested in the history or consequences of life history patterns, it is also clear that a number of larval forms do not fit neatly into either of these general categories. Here we review studies of these intermediate larval forms, focusing on descriptions of larvae known as facultative feeders. Recent descriptions of larval development suggest that facultative feeders and other intermediate larval forms are not as rare as commonly assumed. We assess the importance of these forms for models of life‐history evolution and call for a more‐detailed and nuanced view of larval biology to account for their existence. Clearer knowledge of the phylogenetic distribution and frequency of occurrence of larvae that exhibit intermediate nutritional requirements is also essential for evaluating current ideas on evolutionary transitions between planktotrophy and lecithotrophy. Finally, intermediate larval types provide valuable and underutilized opportunities for testing hypotheses in the fields of larval ecology and the evolution of development.
Brachyury‐downstream gene sets in a chordate, Ciona intestinalis: integrating notochord specification, morphogenesis and chordate evolution
Authors: Hotta Kohji , Takahashi Hiroki , Satoh Nori , Gojobori Takashi
Published: August 2010

SUMMARY
In vertebrates, Brachyury, a T‐box transcription factor gene, seems to have a dual role in the differentiation of axial midline mesoderm cells into notochord and gastrulation cell movements regulated by non‐canonical Wnt/planar cell polarity (Wnt/PCP) signaling. To understand the function of Brachyury‐downstream genes in chordate embryos, from a series of our survey on differential expression, including subtractive hybridization, dot‐blot assays, EST sequences and the expression patterns in whole‐mount in situ hybridization at embryonic stages, we developed a knowledge database called “CINOBI: CionaNotochord and Brachyury‐downstream gene Index” to create comprehensive catalogues of Brachyury‐downstream gene sets in Ciona intestinalis. Combining genome and large‐scale cDNA data, we were able to characterize 450 non‐redundant Brachyury‐downstream genes: Twenty‐four genes were newly annotated as notochord‐expressed genes. Several genes are components of signaling pathways such as Wnt/PCP, NfκB and TGF‐β signaling. We propose that Brachyury is linked to these pathways regulating the expression of each component, and such a regulatory mechanism might be conserved among chordates.
Cubozoan crystallins: evidence for convergent evolution of pax regulatory sequences
Authors: Kozmik Zbynek , Swamynathan Shivalingappa K. , Ruzickova Jana , Jonasova Kristyna , Paces Vaclav , Vlcek Cestmir , Piatigorsky Joram
Published: August 2010

SUMMARY
Cnidaria is the earliest‐branching metazoan phylum containing a well‐developed, lens‐containing visual system located on specialized sensory structures called rhopalia. Each rhopalium in a cubozoan jellyfish Tripedalia cystophora has a large and a small complex, camera‐type eye with a cellular lens containing distinct families of crystallins. Here, we have characterized J2‐crystallin and its gene in T. cystophora. The J2‐crystallin gene is composed of a single exon and encodes a 157‐amino acid cytoplasmic protein with no apparent homology to known proteins from other species. The non‐lens expression of J2‐crystallin suggests nonoptical as well as crystallin functions consistent with the gene‐sharing strategy that has been used during evolution of lens crystallins in other invertebrates and vertebrates. Although nonfunctional in transfected mammalian lens cells, the J2‐crystallin promoter is activated by the jellyfish paired domain transcription factor PaxB in co‐transfection tests via binding to three paired domain sites. PaxB paired domain‐binding sites were also identified in the PaxB‐regulated promoters of the J1A‐ and J1B‐crystallin genes, which are not homologous to the J2‐crystallin gene. Taken together with previous studies on the regulation of the diverse crystallin genes, the present report strongly supports the idea that crystallin recruitment of multifunctional proteins was driven by convergent changes involving Pax (as well as other transcription factors) in the promoters of nonhomologous genes within and between species as well as within gene families.
Co‐option and dissociation in larval origins and evolution: the sea urchin larval gut
Authors: Love Alan C. , Lee Abigail E. , Andrews Mary E. , Raff Rudolf A.
Published: August 2010

SUMMARY
The origin of marine invertebrate larvae has been an area of controversy in developmental evolution for over a century. Here, we address the question of whether a pelagic “larval” or benthic “adult” morphology originated first in metazoan lineages by testing the hypothesis that particular gene co‐option patterns will be associated with the origin of feeding, indirect developing larval forms. Empirical evidence bearing on this hypothesis is derivable from gene expression studies of the sea urchin larval gut of two closely related but differently developing congenerics, Heliocidaris tuberculata (feeding indirect‐developing larva) and H. erythrogramma (nonfeeding direct developer), given two subsidiary hypotheses. (1) If larval gut gene expression in H. tuberculata was co‐opted from an ancestral adult expression pattern, then the gut expression pattern will remain in adult H. erythrogramma despite its direct development. (2) Genes expressed in the larval gut of H. tuberculata will not have a coordinated expression pattern in H. erythrogramma larvae due to loss of a functional gut. Five structural genes expressed in the invaginating archenteron of H. tuberculata during gastrulation exhibit substantially different expression patterns in H. erythrogramma with only one remaining endoderm specific. Expression of these genes in the adult of H. erythrogramma and larval gut of H. tuberculata, but not in H. erythrogramma larval endoderm, supports the hypothesis that they first played roles in the formation of adult structures and were subsequently recruited into larval ontogeny during the origin and evolution of feeding planktotrophic deuterostome larvae.
MicroRNA‐183 family conservation and ciliated neurosensory organ expression
Authors: Pierce Marsha L. , Weston Michael D. , Fritzsch Bernd , Gabel Harrison W. , Ruvkun Gary , Soukup Garrett A.
Published: August 2010

SUMMARY
MicroRNAs (miRNAs) are an integral component of the metazoan genome and affect posttranscriptional repression of target messenger RNAs. The extreme phylogenetic conservation of certain miRNAs suggests their ancient origin and crucial function in conserved developmental processes. We demonstrate that highly conserved miRNA‐183 orthologs exist in both deuterostomes and protostomes and their expression is predominant in ciliated ectodermal cells and organs. The miRNA‐183 family members are expressed in vertebrate sensory hair cells, in innervated regions of invertebrate deuterostomes, and in sensilla of Drosophila and C. elegans. Thus, miRNA‐183 family member expression is conserved in possibly homologous but morphologically distinct sensory cells and organs. The results suggest that miR‐183 family members contribute specifically to neurosensory development or function, and that extant metazoan sensory organs are derived from cells that share genetic programs of common evolutionary origin.
Developmental basis of limb length in rodents: evidence for multiple divisions of labor in mechanisms of endochondral bone growth
Authors: Rolian Campbell
Published: August 2010

SUMMARY
Mammals are remarkably diverse in limb lengths and proportions, but the number and kind of developmental mechanisms that contribute to length differences between limb bones remain largely unknown. Intra‐ and interspecific differences in bone length could result from variations in the cellular processes of endochondral bone growth, creating differences in rates of chondrocyte proliferation or hypertrophy, variation in the shape and size of chondrocytes, differences in the number of chondrocytes in precursor populations and throughout growth, or a combination of these mechanisms. To address these questions, this study compared cellular mechanisms of endochondral bone growth in cross‐sectional ontogenetic series of the appendicular skeleton of two rodent species: the mouse (Mus musculus) and Mongolian gerbil (Meriones unguiculatus). Results indicate that multiple cellular processes of endochondral bone growth contribute to phenotypic differences in limb bone length. The data also suggest that separate developmental processes contribute to intraspecific length differences in proximal versus distal limb bones, and that these proximo‐distal mechanisms are distinct from mechanisms that contribute to interspecific differences in limb bone length related to body size. These developmental “divisions of labor” are hypothesized to be important features of vertebrate limb development that allow (1) morphology in the autopods to evolve independently of the proximal limb skeleton, and (2) adaptive changes in limb proportions related to locomotion to evolve independently of evolutionary changes in body size.
Something for nothing? Reconstruction of ancestral character states in asterinid sea star development
Authors: Keever Carson C. , Hart Michael W.
Published: August 2010

SUMMARY
Traits from early development mapped onto phylogenetic trees can potentially offer insight into the evolutionary history of development by inferring the states of those characters among ancestors at nodes in the phylogeny. A key and often‐overlooked aspect of such mapping is the underlying model of character evolution. Without a well‐supported and realistic model (“nothing”), character mapping of ancestral traits onto phylogenetic trees might often return results (“something”) that lack a sound basis. Here we reconsider a challenging case study in this area of evolutionary developmental biology: the inference of ancestral states for ecological and morphological characters in the reproduction and larval development of asterinid sea stars. We apply improved analytical methods to an expanded set of asterinid phylogenetic data and developmental character states. This analysis shows that the new methods might generally offer some independent insight into choice of a model of character evolution, but that in the specific case of asterinid sea stars the quantitative features of the model (especially the relative probabilities of different directions of change) have an important effect on the results. We suggest caution in applying ancestral state reconstructions in the absence of an independently corroborated model of character evolution, and highlight the need for such modeling in evolutionary developmental biology.
How Drosophila change their combs: the Hox gene Sex combs reduced and sex comb variation among Sophophora species
Authors: Randsholt Neel B. , Santamaria Pedro
Published: August 2010

SUMMARY
Identification of the events responsible for rapid morphological variation during evolution can help understand how developmental processes are changed by genetic modifications and thus produce diverse body features and shapes. Sex combs, a sexually dimorphic structure, show considerable variation in morphology and numbers among males from related species of Sophophora, a subgenus of Drosophila. To address which evolutionary changes in developmental processes underlie this diversity, we first analyzed the genetic network that controls morphogenesis of a single sex comb in the model D. melanogaster. We show that it depends on positive and negative regulatory inputs from proximo‐distal identity specifying genes, including dachshund, bric à brac, and sex combs distal. All contribute to spatial regulation of the Hox gene Sex combs reduced (Scr), which is crucial for comb formation. We next analyzed the expression of these genes in sexually dimorphic species with different comb numbers. Only Scr shows considerable expression plasticity, which is correlated with comb number variation in these species. We suggest that differences in comb numbers reflect changes of Scr expression in tarsus primordia, and discuss how initial comb formation could have occurred in an ancestral Sophophora fly following regulatory modifications of developmental programs both parallel to and downstream of Scr.
The T‐box genes H15 and optomotor‐blind in the spiders Cupiennius salei, Tegenaria atrica and Achaearanea tepidariorum and the dorsoventral axis of arthropod appendages
Authors: Janssen Ralf , Feitosa Natalia M. , Damen Wim G.M. , Prpic Nikola‐Michael
Published: August 2010

SUMMARY
Dorsoventral axis formation in the legs of the fly Drosophila melanogaster requires the T‐box genes optomotor‐blind (omb) and H15. Evolutionary conservation of the patterning functions of these genes is unclear, because data on H15 expression in the spider Cupiennius salei did not support a general role of H15 in ventral fate specification. However, H15 has a paralogous gene, midline (mid) in Drosophila and H15 duplicates are also present in Cupiennius and the millipede Glomeris marginata. H15 therefore seems to have been subject to gene duplication opening the possibility that the previous account on Cupiennius has overlooked one or several paralogs. We have studied omb‐ and H15‐related genes in two additional spider species, Tegenaria atrica and Achearanea tepidariorum and show that in both species one of the H15 genes belongs to a third group of spider H15 genes that has an expression pattern very similar to the H15 pattern in Drosophila. The expression patterns of all omb‐related genes are also very similar to the omb expression pattern in Drosophila. These data suggest that the dorsoventral patterning functions of omb and H15 are conserved in the arthropods and that the previous conclusions were based on an incomplete data set in Cupiennius. Our results emphasize the importance of a broad taxon sampling in comparative studies.
Diverged and conserved aspects of heart formation in a spider
Authors: Janssen Ralf , Damen Wim G.M.
Published: August 2010

SUMMARY
Heart development exhibits some striking similarities between vertebrates and arthropods, for example in both cases the heart develops as a linear tube from mesodermal cells. Furthermore, the underlying molecular pathways exhibit a significant number of similarities between vertebrates and the fruit fly Drosophila, suggesting a common origin of heart development in the last common ancestor of flies and vertebrates. However, there is hardly any molecular data from other animals. Here we show that many of the key genes are also active in heart development in the spider Cupiennius salei. Spiders belong to the chelicerates and are distantly related to insects with respect to the other arthropods. The tinman/Nkx2.5 ortholog is the first gene to be specifically expressed in the presumptive spider heart, like in flies and vertebrates. We also show that tinman is expressed in a similar way in the beetle Tribolium castaneum. Taken together this demonstrates that tinman has a conserved role in the specification of the arthropod heart. In addition, we analyzed the expression of other heart genes (decapentaplegic, Wnt5, H15, even‐skipped, and Mef2 ) in Cupiennius. The expression of these genes suggests that the genetic pathway of heart development may be largely conserved among arthropods. However, a major difference is seen in the earlier expression of the even‐skipped gene in the developing spider heart compared with Drosophila, implying that the role of even‐skipped in heart formation might have changed during arthropod evolution. The most striking finding, however, is that in addition to the dorsal tissue of the fourth walking leg segment and the opisthosomal segments, we discovered tinman‐expressing cells that arise from a position dorsal to the cephalic lobe and that contribute to the anterior dorsal vessel. In contrast to the posterior heart tissue, these cells do not express the other heart genes. The spider heart thus is composed of two distinct populations of cells.
Rapid shape divergences between natural and introduced populations of a horned beetle partly mirror divergences between species
Authors: Pizzo Astrid , Roggero Angela , Palestrini Claudia , Moczek Armin P. , Rolando Antonio
Published: August 2010

SUMMARY
Onthophagus taurus is a polyphenic beetle in which males express alternative major (horned) and minor (hornless) morphologies largely dependent on larval nutrition. O. taurus was originally limited to a Turanic–European–Mediterranean distribution, but became introduced to several exotic regions in the late 1960s. Using geometric morphometrics, we investigate the present‐day morphological shape differentiation patterns among native (Italian) and introduced (Western Australian and Eastern US) populations. We then contrast these divergences to those observed between native O. taurus and its sympatric sister species O. illyricus. Our analysis failed to find significant divergences between O. taurus populations in external morphological traits (head, pronotum) when analyses were conducted separately for each sex. However, when sexes and male morphs were analyzed together, three important differences among populations emerged. First, relative warp analyses showed that native and introduced populations diverged in certain shape components that normally distinguish major and minor male morphs. Second, comparison of covariation of body regions (head vs. pronotum) in the three populations showed that populations diverged in the nature of this covariation, suggesting that different body regions are not totally constrained to evolve in concert. Lastly, and most importantly, the analysis of genitalic shape revealed little to no divergence of female genitalia, but unexpected substantial differentiation of male genitalia among the three O. taurus populations. This suggests that genitalic shape divergence can occur extremely rapidly even in the absence of sympatry and possible reinforcement, and that the genitalia of males and females may diverge independent of one another, at least during the early stage of interpopulational divergence. Interpopulation divergences in O. taurus mirrored aspects of interspecific divergences between O. taurus and O. illyricus in some cases but not others.
Multi‐trait evolution in a cave fish,Astyanax mexicanus
Authors: Protas Meredith , Tabansky Inna , Conrad Melissa , Gross Joshua B. , Vidal Oriol , Tabin Clifford J. , Borowsky Richard
Published: August 2010

SUMMARYWhen surface species colonize caves, a characteristic suite of traits eventually evolves over time, regardless of species. The genetic basis of the inevitable appearance of these very similar phenotypes was investigated through quantitative trait loci (QTL) mapping of 12 traits that differ significantly between the recently evolved (<1 Myr). Mexican cave tetra and its surface conspecific. The traits were a representative set, including eye size, pigment cell numbers, chemical sensitivity, body and skull morphology, standard length, and metabolism. We used both single‐ and multi‐trait models for QTL mapping. QTL effects of these traits were significantly clustered in the genome. We mapped 13 regions in the genome with QTL effects on from three to nine traits. These clusters could be multigenic or could represent single locus with pleiotropic alleles. Given the relatively short time available to construct clusters from unlinked genes through genomic rearrangement, and the counterintuitive polarities of some of the substitution effects, we argue that at least some of the clusters must have a pleiotropic basis.
Six major steps in animal evolution: are we derived sponge larvae?
Authors: Nielsen Claus
Published: August 2010

SUMMARYA review of the old and new literature on animal morphology/embryology and molecular studies has led me to the following scenario for the early evolution of the metazoans. The metazoan ancestor, “choanoblastaea,” was a pelagic sphere consisting of choanocytes. The evolution of multicellularity enabled division of labor between cells, and an “advanced choanoblastaea” consisted of choanocytes and nonfeeding cells. Polarity became established, and an adult, sessile stage developed. Choanocytes of the upper side became arranged in a groove with the cilia pumping water along the groove. Cells overarched the groove so that a choanocyte chamber was formed, establishing the body plan of an adult sponge; the pelagic larval stage was retained but became lecithotrophic. The sponges radiated into monophyletic Silicea, Calcarea, and Homoscleromorpha. Homoscleromorph larvae show cell layers resembling true, sealed epithelia. A homoscleromorph‐like larva developed an archenteron, and the sealed epithelium made extracellular digestion possible in this isolated space. This larva became sexually mature, and the adult sponge‐stage was abandoned in an extreme progenesis. This eumetazoan ancestor, “gastraea,” corresponds to Haeckel's gastraea.Trichoplaxrepresents this stage, but with the blastopore spread out so that the endoderm has become the underside of the creeping animal. Another lineage developed a nervous system; this “neurogastraea” is the ancestor of the Neuralia. Cnidarians have retained this organization, whereas the Triploblastica (Ctenophora+Bilateria), have developed the mesoderm. The bilaterians developed bilaterality in a primitive form in the Acoelomorpha and in an advanced form with tubular gut and long Hox cluster in the Eubilateria (Protostomia+Deuterostomia).

It is indicated that the major evolutionary steps are the result of suites of existing genes becoming co‐opted into new networks that specify new structures.

The evolution of the eumetazoan ancestor from a progenetic homoscleromorph larva implies that we, as well as all the other eumetazoans, are derived sponge larvae.
AINTEGUMENTA homolog expression in Gnetum (gymnosperms) and implications for the evolution of ovulate axes in seed plants
Authors: Yamada Toshihiro , Hirayama Yumiko , Imaichi Ryoko , Kato Masahiro
Published: August 2010

SUMMARY
The expression of GpANTL1, a homolog of AINTEGUMENTA (ANT) found in the gymnosperm Gnetum parvifolium, was analyzed by RT‐PCR and in situ hybridization. GpANTL1 was expressed in the leaf primordia, root tips, and young ovules. In the ovulate axis, expression was detected as four distinct rings around the outer, middle, and inner envelope primordia as well as around the nucellar tip. This pattern of expression is similar to that of ANT in Arabidopsis thaliana. A comparison of the expression of GpANTL1 with that of PtANTL1 in the conifer Pinus thunbergii suggests that the integrated expression of PtANTL1 may have been caused by congenital fusion of the integument, ovuliferous scale, and bract.
Evolutionary insights into the unique electromotility motor of mammalian outer hair cells
Authors: Okoruwa Oseremen E. , Weston Michael D. , Sanjeevi Divvya C. , Millemon Amanda R. , Fritzsch Bernd , Hallworth Richard , Beisel Kirk W.
Published: August 2010

SUMMARY
Prestin (SLC26A5) is the molecular motor responsible for cochlear amplification by mammalian cochlea outer hair cells and has the unique combined properties of energy‐independent motility, voltage sensitivity, and speed of cellular shape change. The ion transporter capability, typical of SLC26A members, was exchanged for electromotility function and is a newly derived feature of the therian cochlea. A putative minimal essential motif for the electromotility motor (meEM) was identified through the amalgamation of comparative genomic, evolution, and structural diversification approaches. Comparisons were done among nonmammalian vertebrates, eutherian mammalian species, and the opossum and platypus. The opossum and platypus SLC26A5 proteins were comparable to the eutherian consensus sequence. Suggested from the point‐accepted mutation analysis, the meEM motif spans all the transmembrane segments and represented residues 66–503. Within the eutherian clade, the meEM was highly conserved with a substitution frequency of only 39/7497 (0.5%) residues, compared with 5.7% in SLC26A4 and 12.8% in SLC26A6 genes. Clade‐specific substitutions were not observed and there was no sequence correlation with low or high hearing frequency specialists. We were able to identify that within the highly conserved meEM motif two regions, which are unique to all therian species, appear to be the most derived features in the SLC26A5 peptide.
Phenotypic plasticity in insects: the effects of substrate color on the coloration of two ground‐hopper species
Authors: Hochkirch Axel , Deppermann Jana , Gröning Julia
Published: August 2010

SUMMARY
The question of how phenotypic variation is maintained within populations has long been a central issue in evolutionary biology. Most of these studies focused on the maintenance of genetic variability, but the phenotype of organisms may also be influenced by environmental cues experienced during ontogeny. Color polymorphism has received particular attention in evolutionary studies as it has strong fitness consequences. However, if body coloration is influenced by the environment, any conclusions on evolutionary consequences of fitness trade‐offs can be misleading. Here we present data from a laboratory experiment on the influence of substrate color on three aspects of the coloration of two ground‐hopper species, Tetrix subulata and Tetrix ceperoi. We reared hatchlings either on dark or on light substrates, using a split‐brood design. Although the type of pronotal pattern changed mainly in response to nymphal development, the basic color was strongly influenced by the substrate color. In both species, black and dark olive color morphs were found more frequently on the dark substrate, whereas the gray color morph dominated on the light substrate. These findings have considerable implications for our understanding of color morph evolution as they show that color polymorphism may not only be maintained by natural selection acting on discrete color morphs, but also by phenotypic plasticity, which enables organisms to adjust to the environmental conditions experienced during ontogeny. This facultative morphology is opposing to the prevailing view of color morph adaptation, which assumes a purely genetic determination and co‐evolution of discrete color morphs with life history traits.
Plasticity in mRNA expression and localization of orthodenticle within higher Diptera
Authors: Schetelig Marc F. , Schmid Bernhard G. M. , Zimowska Grazyna , Wimmer Ernst A.
Published: August 2010

SUMMARY
orthodenticle (otd) genes are found throughout the animal kingdom and encode well‐studied homeodomain transcription factors that share conserved functions in cephalization, head segmentation, brain patterning, and the differentiation of photoreceptors. Otd proteins have been proposed as ancestral key players in anterior determination despite a high level of variation in gene expression at early developmental stages: otd is expressed strictly zygotically in the dipteran Drosophila melanogaster, while otd1 mRNA is contributed maternally to the embryo in the coleopteran Tribolium castaneum and maternal otd1 mRNA is localized to the anterior and posterior pole of the oocyte in the hymopteran Nasonia vitripennis. Here we demonstrate that such changes in otd mRNA expression and localization do not need to represent large phylogenetic distances but can occur even within closely related taxa. We show maternal otd expression in the medfly Ceratitis capitata and maternally localized otd mRNA in the caribfly Anastrepha suspensa, two cyclorrhaphan species closely related to Drosophila. This indicates considerable plasticity in expression and mRNA localization of key developmental genes even within short evolutionary distances.
Loss and gain of the juvenile rudiment and metamorphic competence during starvation and feeding of bryozoan larvae
Authors: Strathmann Richard R. , Foley Gerard P. , Hysert Alana N.
Published: August 2010

SUMMARY
In many animals, larval structures and juvenile rudiments develop independently. One advantage of this independence is that juvenile rudiments can be expended as a nutrient reserve or for energy conservation. When bryozoan cyphonautes larvae were starved, structures required for settlement and metamorphosis shrank. When the larvae were again fed, these structures grew back. Starvation reduced the size of both the internal sac, a rudiment of postlarval juvenile structures, and the pyriform organ, which functions in sensing and crawling on the substratum at settlement. In contrast, starvation affected neither the size of the larval shell nor the lengths of the ciliary bands used in swimming and feeding. Starved larvae that had reduced the pyriform organ and internal sac did not metamorphose in response to stimuli from a laminarian alga. The laminarian alga did stimulate metamorphosis of the same larvae after renewed feeding, when the larvae had regrown these structures. Thus starved larvae expended body parts needed for settlement and metamorphosis when food was scarce while retaining structures for feeding, swimming, and defense. Starved larvae thereby retained the capacity to regrow structures needed for settlement and metamorphosis when they again encountered food. Advantages from expendable juvenile rudiments may enhance selection for their being developmentally distinct from structures for larval swimming and feeding.
Silencing of an abdominal Hox gene during early development is correlated with limb development in a crustacean trunk
Authors: Hsia Cheryl C. , Paré Adam C. , Hannon Michael , Ronshaugen Matthew , McGinnis William
Published: August 2010

SUMMARY
We tested whether Artemia abd‐A could repress limbs in Drosophila embryos, and found that although abd‐A transcripts were produced, ABD‐A protein was not. Similarly, developing Artemia epidermal cells showed expression of abd‐A transcripts without accumulation of ABD‐A protein. This finding in Artemia reveals a new variation in Hox gene function that is associated with morphological evolution. In this case, a HOX protein expression pattern is completely absent during early development, although the HOX protein is expressed at later stages in the central nervous system in a “homeotic‐like” pattern. The combination of an absence of ABD‐A protein expression in the Artemia limb primordia and the weak repressive function of Artemia UBX protein on the limb‐promoting gene Dll are likely to be two reasons why homonomous limbs develop throughout the entire Artemia trunk.
Evolutionary origin of the insect wing via integration of two developmental modules
Authors: Niwa Nao , Akimoto‐Kato Ai , Niimi Teruyuki , Tojo Koji , Machida Ryuichiro , Hayashi Shigeo
Published: August 2010

SUMMARY
Insect wing is a key evolutionary innovation for insect radiation, but its origins and intermediate forms are absent from the fossil record. To understand the ancestral state of the wing, expression of three key regulatory genes in insect wing development, wingless (wg), vestigial (vg), and apterous (ap) was studied in two basal insects, mayfly and bristletail. These basal insects develop dorsal limb branches, tracheal gill and stylus, respectively, that have been considered candidates for wing origin. Here we show that wg and vg are expressed in primordia for tracheal gill and stylus. Those primordia are all located in the lateral body region marked by down‐regulation of early segmental wg stripes, but differ in their dorsal–ventral position, indicating their positions drifted within the lateral body region. On the other hand, ap expression was detected in terga of mayfly and bristletail. Notably, the extensive outgrowth of the paranotal lobe of apterygote bristletail developed from the border of ap‐expressing tergal margin, and also expressed wg and vg. The data suggest that two regulatory modules involving wg–vg are present in apterygote insects: one associated with lateral body region and induces stick‐like dorsal limb branches, the other associated with the boundary of dorsal and lateral body regions and the flat outgrowth of their interface. A combinatorial model is proposed in which dorsal limb branch was incorporated into dorsal–lateral boundary and acquired flat limb morphology through integration of the two wg–vg modules, allowing rapid evolution of the wing.
Myogenesis in two polyclad platyhelminths with indirect development, Pseudoceros canadensis and Stylostomum sanjuania
Authors: Semmler Henrike , Wanninger Andreas
Published: August 2010

SUMMARY
Myogenesis of two representatives of Platyhelminthes, Stylostomum sanjuania and Pseudoceros canadensis, was followed from egg deposition until well‐differentiated free‐swimming larval stages, using F‐actin staining and confocal laserscanning microscopy. Zonulae adhaerentes are the only structures to stain before 50% of development between egg deposition and hatching in S. sanjuania, and before 67% of development in P. canadenis. Subsequently, irregular fibers appear in the embryo, followed by a helicoid muscle close to the apical pole. Three longitudinal muscle pairs form, of which the dorsal pair remains more pronounced than the others. Gradually, new muscles form by branching or from double‐stranded muscle zones adjacent to existing muscles. This results in an elaborate muscular bodywall that consists of a single helicoid muscle as well as multiple circular and longitudinal muscles. Diverse retractor muscles insert at the sphincter muscles around the stomodeum. The overall arrangement and formation mode of the larval musculature appears very similar in both species, although only P. canadensis has a primary circular muscle posterior to the helicoid muscle. Muscle formation in the apical region of the embryo precedes that at the abapical pole and the primary longitudinal muscles form slightly later than the primary circular muscles. Myogenesis and larval myoanatomy appears highly conserved among polyclad flatworms, but differs significantly from that of other trochozoan clades. Our data suggest that the larval muscular ground pattern of polyclad larvae comprises a bodywall consisting of a helicoid muscle, circular and longitudinal muscles, several retractor muscles, and sphincter muscles around the stomodeum.
Difference in larval type explains patterns of nonsynonymous substitutions in two ancient paralogs of the histone H3 gene in sea stars
Authors: Foltz David W. , Mah Christopher L.
Published: August 2010

SUMMARY
Paralogous genes frequently show differences in patterns and rates of substitution that are typically attributed to different selection regimes, mutation rates, or local recombination rates. Here, two anciently diverged paralogous copies of the histone H3 gene in sea stars, the tandem‐repetitive early‐stage gene and a newly isolated gene with lower copy number that was termed the “putative late‐stage histone H3 gene” were analyzed in 69 species with varying mode of larval development. The two genes showed differences in relative copy number, overall substitution rates, nucleotide composition, and codon usage, but similar patterns of relative nonsynonymous substitution rates, when analyzed by the dN/dS ratio. Sea stars with a nonpelagic and nonfeeding larval type (i.e., brooding lineages) were observed to have dN/dS ratios that were larger than for nonbrooders but equal between the two paralogs. This finding suggested that demographic differences between brooding and nonbrooding lineages were responsible for the elevated dN/dS ratios observed for brooders and refuted a suggestion from a previous analysis of the early‐stage gene that the excess nonsynonymous substitutions were due to either (1) gene expression differences at the larval stage between brooders and nonbrooders or (2) the highly repetitive structure of the early‐stage histone H3 gene.
Expression of ovule and integument‐associated genes in reduced ovules of Santalales
Authors: Brown Ryan H. , Nickrent Daniel L. , Gasser Charles S.
Published: August 2010

SUMMARYSantalales comprise mainly parasitic plants including mistletoes and sandalwoods. Bitegmic ovules similar to those found in most other angiosperms are seen in many members of the order, but other members exhibit evolutionary reductions to the unitegmic and ategmic conditions. In some mistletoes, extreme reduction has resulted in the absence of emergent ovules such that embryo sacs appear to remain embedded in placental tissues. Three santalalean representatives (Comandra, Santalum, andPhoradendron), displaying unitegmic, and ategmic ovules, were studied. Observed ovule morphologies were consistent with published reports, includingPhoradendron serotinum, which we interpret as having reduced ategmic ovules, consistent with earlier reports on this species. For further understanding of the nature of the ovule reductions we isolated orthologs of theArabidopsisgenesAINTEGUMENTA(ANT) andBELL1(BEL1), which are associated with ovule development in this species. We observed ovular expression ofANTandBEL1in patterns largely resembling those seen in the integumented ovules ofArabidopsis. These genes were found to be expressed in the integument of unitegmic ovules and in the surface layers of ategmic ovules, and in some cases, expression ofBEL1was also observed in the surrounding carpel tissue. We hypothesize that ategmic ovules derive from a fusion of the integuments with the nucellus or that the nucellus has taken on some of the characteristics confined to integuments in ancestral species.
Application of Assisted Natural Regeneration to Restore Degraded Tropical Forestlands
Authors: Shono Kenichi , Cadaweng Ernesto A. , Durst Patrick B.
Published: August 2010

Assisted natural regeneration (ANR) is a simple, low‐cost forest restoration method that can effectively convert deforested lands of degraded vegetation to more productive forests. The method aims to accelerate, rather than replace, natural successional processes by removing or reducing barriers to natural forest regeneration such as soil degradation, competition with weedy species, and recurring disturbances (e.g., fire, grazing, and wood harvesting). Compared to conventional reforestation methods involving planting of tree seedlings, ANR offers significant cost advantages because it reduces or eliminates the costs associated with propagating, raising, and planting seedlings. It is most effectively utilized at the landscape level in restoring the protective functions of forests such as watershed protection and soil conservation. ANR techniques are flexible and allow for the integration of various values such as timber production, biodiversity recovery, and cultivation of crops, fruit trees, and non‐timber forest products in the restored forest. This paper describes the steps of applying ANR and conditions under which it will be most effective. It also discusses ANR’s comparative advantages as well as some of its constraints.