Molekulargenetische und bestäubungsbiologische Untersuchungen der natürlich bestandsbildenden floralen homöotischen Spe-Variante des Hirntentäschels (Capsella bursa-pastoris)

Homöotische Veränderungen haben innerhalb der Evolution der Blüte eine beachtliche Rolle gespielt. Inwiefern diese spontan entstandenen floralen Varietäten allerdings überleben und in der Natur etablieren konnten ist unklar und aufgrund ihres seltenen Auftretens in der Natur schwer zu untersuchen. Um das evolutionäre Potential solcher Varietäten besser zu verstehen, wurde in dieser Arbeit eine Sippe von Capsella bursa-pastoris (Hirtentäschel; Familie Brassicaceae) aus Gau-Odernheim (Rheinhessen) sowie aus Warburg, bei denen aufgrund einer Mutation im co-dominanten Stamenoid Petals (Spe) Locus die Petalen aller Blüten vollständig in Stamina umgewandelt sind, molekulargenetisch als auch bestäubungsbiologisch untersucht. Im Übersichtsartikel wurden bekannte Fakten über Homöosis und deren Rolle in der Blütenentwicklung zusammengestellt, um das Potential von C. bursa-pastoris als Modellpflanze darzustellen und die Spe-Variante einzuführen. Als Arbeitshypothese bezüglich der molekularen Ursache des Phänomens diente das bekannte ABC-Modell der Blüte, wonach Stamina durch florale homöotische Gene der Klassen B und C spezifiziert werden. Da Klasse B-Gene normalerweise ohnehin im 2. Blütenkreis exprimiert werden, wurde eine ektopische Expression von floralen homöotischen Klasse C-Genen im 2. Blütenwirtel postuliert und später nachgewiesen. Außerdem wurden Möglichkeiten aufgeführt, dieses Phänomen experimentell zu untersuchen, sowohl aus molekulargenetischer als auch ökologischer Sicht. Über die Suche nach SNPs in den Kandidatengenen (Klasse C-Gene) zwischen Wildtyp und Spe-Variante, sowie anschließender Genotypisierung einer segregierenden (1:3) F2-Population mittels Pyrosequenzierung konnte der für die Transformation mutmaßlich verantwortliche Locus chromosomal lokalisiert werden. Es handelt sich dabei um eine enge Kopplung von CbpAGa an den Spe-Phänotyp mit einer Sequenzveränderung im regulatorisch wirksamen 2. Intron. Unsere Ergebnisse stützen die Hypothese, dass cis-regulatorische Veränderungen in einem der floralen homöotischen Klasse C-Gene von C. bursa-pastoris dem Spe-Phänomen zugrunde liegen. Untersuchungen an einer weiteren Spe-Population (Warburg) zeigten ein ähnliches Expressionsmuster von CbpAG sowie exakt den gleichen Sequenzpolymorphismus im 2. Intron von CbpAGa. Im 2. Themenkomplex dieser Arbeit wurden die Auswirkungen solch drastischer morphologischer Veränderungen, wie die Umwandlung von Petalen in Stamina auf die Fitness von Spe-Variante gegenüber Wildtyp untersucht. In Freilanduntersuchungen konnten Daten zu potentiellen Bestäubern, deren Besuchshäufigkeit und die Samenproduktion erhoben werden. Zusätzlich wurden Keimversuche und Duftstoffanalysen durchgeführt. Die Ergebnisse zeigen, dass die ähnliche Fitness von Spe- und Wildtyp-Pflanzen auf ein komplexes Zusammenspiel von Pflanzenarchitektur und Keimstrategie zurückzuführen ist und dass Blütenstruktur und Blütenbesuche nur eine untergeordnete Rolle spielen, höchstwahrscheinlich aufgrund der vorherrschenden Selbstbestäubung bei C. bursa-pastoris

Muscle development in the shark Scyliorhinus canicula: implications for the evolution of the gnathostome head and paired appendage musculature

Abstract Background The origin of jawed vertebrates was marked by profound reconfigurations of the skeleton and muscles of the head and by the acquisition of two sets of paired appendages. Extant cartilaginous fish retained numerous plesiomorphic characters of jawed vertebrates, which include several aspects of their musculature. Therefore, myogenic studies on sharks are essential in yielding clues on the developmental processes involved in the origin of the muscular anatomy. Results Here we provide a detailed description of the development of specific muscular units integrating the cephalic and appendicular musculature of the shark model, Scyliorhinus canicula. In addition, we analyze the muscle development across gnathostomes by comparing the developmental onset of muscle groups in distinct taxa. Our data reveal that appendicular myogenesis occurs earlier in the pectoral than in the pelvic appendages. Additionally, the pectoral musculature includes muscles that have their primordial developmental origin in the head. This culminates in a tight muscular connection between the pectoral girdle and the cranium, which founds no parallel in the pelvic fins. Moreover, we identified a lateral to ventral pattern of formation of the cephalic muscles, that has been equally documented in osteichthyans but, in contrast with these gnathostomes, the hyoid muscles develop earlier than mandibular muscle in S. canicula. Conclusion Our analyses reveal considerable differences in the formation of the pectoral and pelvic musculatures in S. canicula, reinforcing the idea that head tissues have contributed to the formation of the pectoral appendages in the common ancestor of extant gnathostomes. In addition, temporal differences in the formation of some cranial muscles between chondrichthyans and osteichthyans might support the hypothesis that the similarity between the musculature of the mandibular arch and of the other pharyngeal arches represents a derived feature of jawed vertebrates

Anatomical comparison across heads, fore- and hindlimbs in mammals using network models

Animal body parts evolve with variable degrees of integration that nonetheless yield functional adult phenotypes: but, how? The analysis of modularity with Anatomical Network Analysis (AnNA) is used to quantitatively determine phenotypic modules based on the physical connection among anatomical elements, an approach that is valuable to understand developmental and evolutionary constraints. We created anatomical network models of the head, forelimb, and hindlimb of two taxa considered to represent a ‘generalized’ eutherian (placental: mouse) and metatherian (marsupial: opossum) anatomical configuration and compared them with our species, which has a derived eutherian configuration. In these models, nodes represent anatomical units and links represent their physical connection. Here, we aimed to identify: (1) the commonalities and differences in modularity between species, (2) whether modules present a potential phylogenetic character, and (3) whether modules preferentially reflect either developmental or functional aspects of anatomy, or a mix of both. We predicted differences between networks of metatherian and eutherian mammals that would best be explained by functional constraints, versus by constraints of development and/or phylogeny. The topology of contacts between bones, muscles, and bones + muscles showed that, among all three species, skeletal networks were more similar than musculoskeletal networks. There was no clear indication that humans and mice are more alike when compared to the opossum overall, even though their musculoskeletal and skeletal networks of fore- and hindlimbs are slightly more similar. Differences were greatest among musculoskeletal networks of heads and next of forelimbs, which showed more variation than hindlimbs, supporting previous anatomical studies indicating that in general the configuration of the hindlimbs changes less across evolutionary history. Most observations regarding the anatomical networks seem to be best explained by function, but an exception is the adult opossum ear ossicles. These ear bones might form an independent module because the incus and malleus are involved in forming a functional primary jaw that enables the neonate to attach to the teat, where this newborn will complete its development. Additionally, the human data show a specialized digit 1 module (thumb/big toe) in both limb types, likely the result of functional and evolutionary pressures, as our ape ancestors had highly movable big toes and thumbs

Anatomical variations of the deep head of Cruveilhier of the flexor pollicis brevis and its significance for the evolution of the precision grip - Fig 5

<p><b>Palmar view of dissected ulnar and median nerve in hands indicated in A-E.</b> Variability of branching pattern in both nerves is obvious. All hands have a split deep head of Cruveilhier with insertions onto the ulnar and radial proximal phalanx. The ulnar slip is always innervated by the ulnar nerve and the radial slip by the median nerve, except for C (#774R) where the ulnar head receives innervation from both nerves. The recurrent nerve (Rec) of the median nerve innervates the flexor pollicis brevis (FPB), the abductor pollicis brevis (Ab), and the opponens pollicis (Op). The deep palmar ulnar nerve innervates the palmar and dorsal interossei (I) while crossing the palm from medial to lateral (towards the thumb). In the thenar compartment it branches and innervates the adductor pollicis transverse (At) and oblique (Ao) heads, the muscle of Henle (H), and the first dorsal interossei (the terminal I). The innervation of the ulnar (U) and radial (R) heads of the deep head of Cruveilhier is indicated in Red to for better visualization. The palmaris brevis (Pb) is innervated by the superficial branch of the ulnar nerve and the hypothenar muscles, opponens digiti minimi (Om), flexor digiti minimi (Fm), and abductor digiti minimi (Am) are innervated by the deep ulnar nerve. One exception to this pattern is shown in Fig 5A.</p

Cell fate and timing in the evolution of neural crest and mesoderm development in the head region of amphibians and lungfishes

Our research on the evolution of head development focuses on understanding the developmental origins of morphological innovations and involves asking questions like: How flexible (or conserved) are cell fates, patterns of cell migration or the timing of developmental events (heterochrony)? How do timing changes, or changes in life history affect head development and growth? Our 'model system' is a comparison between lungfishes and representatives from all three extant groups of amphibians. Within anuran amphibians, major changes in life history such as the repeated evolution of larval specializations (e.g. carnivory), or indeed the loss of a free-swimming larva, allows us to test for developmental constraints. Cell migration and cell fate are conserved in cranial neural crest cells in all vertebrates studied so far. Patterning and developmental anatomy of cranial neural crest and head mesoderm cells are conserved within amphibians and even between birds, mammals and amphibians. However, the specific formation of hypobranchial muscles from ventral somitic processes shows variation within tetrapods. The evolution of carnivorous larvae in terminal taxa is correlated with changes in both pattern and timing of head skeletal and muscle development. Sequence-heterochronic changes are correlated with feeding mode in terminal taxa and with phylogenetic relatedness in basal branches of the phylogeny. Eye muscles seem to form a developmental module that can evolve relatively independently from other head muscles, at least in terms of timing of muscle differentiation.9 page(s

Day and Napier’s [34, 35] study of the deep head of Cruveilhier compared to the results of the present study.

<p>Day and Napier’s [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187402#pone.0187402.ref034" target="_blank">34</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0187402#pone.0187402.ref035" target="_blank">35</a>] study of the deep head of Cruveilhier compared to the results of the present study.</p

Innervation of the heads of the flexor pollicis brevis.

<p>Innervation of the heads of the flexor pollicis brevis.</p

Schematic drawings of three possible configurations for the deep head of Cruveilhier.

<p><b>A)</b> Overview of muscles attaching onto the proximal phalanx of the thumb. The deep head of Cruveilhier has two heads that insert radialward and ulnarward onto the base of the proximal phalanx 1. <b>B)</b> The deep head of Cruveilhier with only ulnar insertion. In some specimens, like the one depicted here, the most radialward fibers of the oblique head of the adductor pollicis form another slip that can be mistaken for the deep head of Cruveilhier. However, the origin is continuous with the fibers of the rest of the oblique adductor pollicis. <b>C)</b> The deep head of Cruveilhier with only radial insertion. Drawings by Marie Dauenheimer.</p

Innervation of the deep head of Cruveilhier.

<p>Palmar view of right hands. <b>A)</b> The dissection of the radial and median nerve (#766R). After dissection the schematic drawing on the right were done for all hands. <b>B)</b> The median nerve mostly innervates the radial head of the deep head of Cruveilhier. In cases where the median nerve is also innervating the ulnar head the branch usually passes under the tendon of the flexor pollicis longus. The exception is shown here (#779R). Blue scale = 1 cm.</p