Evolution: Molting regulation by ecdysone is conserved in Tardigrada.

Molting is a key feature of Ecdysozoa, but little is known about the regulation of this process in most ecdysozoans. A new study demonstrates that molting is regulated by the ecdysteroid hormone in the tardigrade Hypsibius exemplaris.

Expression of distal limb patterning genes in Hypsibius exemplaris indicate regionalization and suggest distal identity of tardigrade legs.

Background: Panarthropods, a major group of invertebrate animals comprised of arthropods, onychophorans, and tardigrades, are the only limb-bearing members of Ecdysozoa. The complexity and versatility of panarthropod paired limbs has prompted great interest in their development to better understand the formation of these structures and the genes involved in this process. However, studies of limb patterning and development are overwhelmingly focused on arthropods, followed by select work on onychophorans but almost entirely lacking for tardigrades.

Developmental and genomic insight into the origin of the tardigrade body plan.

Tardigrada is an ancient lineage of miniaturized animals. As an outgroup of the well-studied Arthropoda and Onychophora, studies of tardigrades hold the potential to reveal important insights into body plan evolution in Panarthropoda. Previous studies have revealed interesting facets of tardigrade development and genomics that suggest that a highly compact body plan is a derived condition of this lineage, rather than it representing an ancestral state of Panarthropoda.

Cambrian lobopodians shed light on the origin of the tardigrade body plan.

Phylum Tardigrada (water bears), well known for their cryptobiosis, includes small invertebrates with four paired limbs and is divided into two classes: Eutardigrada and Heterotardigrada. The evolutionary origin of Tardigrada is known to lie within the lobopodians, which are extinct soft-bodied worms with lobopodous limbs mostly discovered at sites of exceptionally well-preserved fossils. Contrary to their closest relatives, onychophorans and euarthropods, the origin of morphological characters of tardigrades remains unclear, and detailed comparison with the lobopodians has not been well explored.

The embryonic origin of primordial germ cells in the tardigrade Hypsibius exemplaris.

Primordial germ cells (PGCs) give rise to gametes - cells necessary for the propagation and fertility of diverse organisms. Current understanding of PGC development is limited to the small number of organisms whose PGCs have been identified and studied. Expanding the field to include little-studied taxa and emerging model organisms is important to understand the full breadth of the evolution of PGC development.

The Embryonic Origin of Primordial Germ Cells in the Tardigrade .

Primordial germ cells (PGCs) give rise to gametes â€" cells necessary for the propagation and fertility of diverse organisms. Current understanding of PGC development is limited to the small number of organisms whose PGCs have been identified and studied. Expanding the field to include little-studied taxa and emerging model organisms is important to understand the full breadth of the evolution of PGC development.

Extensive loss of Wnt genes in Tardigrada.

Background: Wnt genes code for ligands that activate signaling pathways during development in Metazoa. Through the canonical Wnt (cWnt) signaling pathway, these genes regulate important processes in bilaterian development, such as establishing the anteroposterior axis and posterior growth. In Arthropoda, Wnt ligands also regulate segment polarity, and outgrowth and patterning of developing appendages.

Loss of intermediate regions of perpendicular body axes contributed to miniaturization of tardigrades.

Tardigrades have a miniaturized body plan. Miniaturization in tardigrades is associated with the loss of several organ systems and an intermediate region of their anteroposterior (AP) axis. However, how miniaturization has affected tardigrade legs is unclear.

Embryonic In Situ Hybridization for the Tardigrade .

In situ hybridization is a method for visualizing embryonic gene expression that is amenable to nonmodel systems. Here, an in situ hybridization protocol is presented for the tardigrade This method allows gene expression to be visualized directly and with fluorescence microscopy.

Embryonic Immunostaining for the Tardigrade .

Immunostaining is a method used to visualize the localization of proteins in fixed tissue. Many antibodies are available that recognize specific proteins in a wide diversity of organisms, which makes this method ideal for investigating gene expression patterns in nonmodel animal systems. This protocol describes immunostaining for studies of embryogenesis in the tardigrade .

Analyses of nervous system patterning genes in the tardigrade illuminate the evolution of panarthropod brains.

Background: Both euarthropods and vertebrates have tripartite brains. Several orthologous genes are expressed in similar regionalized patterns during brain development in both vertebrates and euarthropods. These similarities have been used to support direct homology of the tripartite brains of vertebrates and euarthropods.

A Hypothesis for the Composition of the Tardigrade Brain and its Implications for Panarthropod Brain Evolution.

Incredibly disparate brain types are found in Metazoa, which raises the question of how this disparity evolved. Ecdysozoa includes representatives that exhibit ring-like brains-the Cycloneuralia-and representatives that exhibit ganglionic brains-the Panarthropoda (Euarthropoda, Onychophora, and Tardigrada). The evolutionary steps leading to these distinct brain types are unclear.

Segmentation in Tardigrada and diversification of segmental patterns in Panarthropoda.

The origin and diversification of segmented metazoan body plans has fascinated biologists for over a century. The superphylum Panarthropoda includes three phyla of segmented animals-Euarthropoda, Onychophora, and Tardigrada. This superphylum includes representatives with relatively simple and representatives with relatively complex segmented body plans.

The Compact Body Plan of Tardigrades Evolved by the Loss of a Large Body Region.

The superphylum Panarthropoda (Arthropoda, Onychophora, and Tardigrada) exhibits a remarkable diversity of segment morphologies, enabling these animals to occupy diverse ecological niches. The molecular identities of these segments are specified by Hox genes and other axis patterning genes during development [1, 2]. Comparisons of molecular segment identities between arthropod and onychophoran species have yielded important insights into the origins and diversification of their body plans [3-9].

Evidence for extensive horizontal gene transfer from the draft genome of a tardigrade.

Horizontal gene transfer (HGT), or the transfer of genes between species, has been recognized recently as more pervasive than previously suspected. Here, we report evidence for an unprecedented degree of HGT into an animal genome, based on a draft genome of a tardigrade, Hypsibius dujardini. Tardigrades are microscopic eight-legged animals that are famous for their ability to survive extreme conditions.

Hox genes require homothorax and extradenticle for body wall identity specification but not for appendage identity specification during metamorphosis of Tribolium castaneum.

The establishment of segment identity is a key developmental process that allows for divergence along the anteroposterior body axis in arthropods. In Drosophila, the identity of a segment is determined by the complement of Hox genes it expresses. In many contexts, Hox transcription factors require the protein products of extradenticle (exd) and homothorax (hth) as cofactors to perform their identity specification functions.

Metamorphic labral axis patterning in the beetle Tribolium castaneum requires multiple upstream, but few downstream, genes in the appendage patterning network.

The arthropod labrum is an anterior appendage-like structure that forms the dorsal side of the preoral cavity. Conflicting interpretations of fossil, nervous system, and developmental data have led to a proliferation of scenarios for labral evolution. The best supported hypothesis is that the labrum is a novel structure that shares development with appendages as a result of co-option.

A functional genetic analysis in flour beetles (Tenebrionidae) reveals an antennal identity specification mechanism active during metamorphosis in Holometabola.

The antenna was the first arthropod ventral appendage to evolve non-leg identity. Models of antennal evolution have been based on comparisons of antennal and leg identity specification mechanisms in Drosophila melanogaster, a species in which appendages develop from highly derived imaginal discs during the larval period. We test for conservation of the Drosophila antennal identity specification mechanism at metamorphosis in Tribolium castaneum and three other flour beetle species (Tribolium confusum, Tribolium brevicornis and Latheticus oryzae) in the family Tenebrionidae.

Extent With Modification: Leg Patterning in the Beetle Tribolium castaneum and the Evolution of Serial Homologs.

Serial homologs are similar structures that develop at different positions within a body plan. These structures share some, but not all, aspects of developmental patterning, and their evolution is thought to be constrained by shared, pleiotropic gene functions. Here we describe the functions of 17 developmental genes during metamorphic development of the legs in the red flour beetle, Tribolium castaneum.

Patterning of the adult mandibulate mouthparts in the red flour beetle, Tribolium castaneum.

Specialized insect mouthparts, such as those of Drosophila, are derived from an ancestral mandibulate state, but little is known about the developmental genetics of mandibulate mouthparts. Here, we study the metamorphic patterning of mandibulate mouthparts of the beetle Tribolium castaneum, using RNA interference to deplete the expression of 13 genes involved in mouthpart patterning. These data were used to test three hypotheses related to mouthpart development and evolution.

Sex-specific gene interactions in the patterning of insect genitalia.

Genitalia play an important role in the life histories of insects, as in other animals. These sexually dimorphic structures evolve rapidly and derive from multiple body segments. Despite the importance of insect genitalia, descriptions of their genetic patterning have been limited to fruit flies.

Effects of lanthanum and cerium on the growth and mineral nutrition of corn and mungbean.

Background And Aims: Plant growth responses to the rare earth elements lanthanum (La) and cerium (Ce) have been reported, but little is known about the effects of these two elements on plant mineral nutrition.

Methods: Corn (Zea mays 'Hycorn 82') and mungbean (Vigna radiata 'Berken') were grown in continuous flowing nutrient solutions containing 0, 0.2, 1.

Cereal phosphate transporters associated with the mycorrhizal pathway of phosphate uptake into roots.

A very large number of plant species are capable of forming symbiotic associations with arbuscular mycorrhizal (AM) fungi. The roots of these plants are potentially capable of absorbing P from the soil solution both directly through root epidermis and root hairs, and via the AM fungal pathway that delivers P to the root cortex. A large number of phosphate (P) transporters have been identified in plants; tissue expression patterns and kinetic information supports the roles of some of these in the direct root uptake pathways.

Altered fungal sensitivity to a plant antimicrobial peptide through over-expression of yeast cDNAs.

A yeast cDNA expression library was screened to identify genes and cellular processes that influence fungal sensitivity to a plant antimicrobial peptide. A plasmid-based, GAL1 promoter-driven yeast cDNA expression library was introduced into a yeast genotype susceptible to the antimicrobial peptide MiAMP1 purified from Macadamia integrifolia. Following a screen of 20,000 cDNAs, three yeast cDNAs were identified that reproducibly provided transformants with galactose-dependent resistance to MiAMP1.