Infection of Medicago truncatula by the root-knot nematode Meloidogyne javanica does not require early nodulation genes

Because of the developmental similarities between root nodules induced by symbiotic rhizobia and root galls formed by parasitic nematodes, we investigated the involvement of nodulation genes in the infection of Medicago truncatula by the root knot nematode (RKN), Meloidogyne javanica. We found that gall formation, including giant cell formation, pericycle and cortical cell division, as well as egg laying, occurred successfully in the non-nodulating mutants nfp1 (nod factor perception1), nin1 (nodule inception1) and nsp2 (nodulation signaling pathway2) and the cytokinin perception mutant cre1 (cytokinin receptor1). Gall and egg formation were significantly reduced in the ethylene insensitive, hypernodulating mutant skl (sickle), and to a lesser extent, in the low nodulation, abscisic acid insensitive mutant latd/nip (lateral root-organ defective/numerous infections and polyphenolics). Despite its supernodulation phenotype, the sunn4 (super numeric nodules4) mutant, which has lost the ability to autoregulate nodule numbers, did not form excessive numbers of galls. Co-inoculation of roots with nematodes and rhizobia significantly reduced nodule numbers compared to rhizobia-only inoculated roots, but only in the hypernodulation mutant skl. Thus, this effect is likely to be influenced by ethylene signaling, but is not likely explained by resource competition between galls and nodules. Co-inoculation with rhizobia also reduced gall numbers compared to nematode-only infected roots, but only in the wild type. Therefore, the protective effect of rhizobia on nematode infection does not clearly depend on nodule number or on Nod factor signaling. Our study demonstrates that early nodulation genes that are essential for successful nodule development are not necessary for nematode-induced gall formation, that gall formation is not under autoregulation of nodulation control, and that ethylene signaling plays a positive role in successful RKN parasitism in M. truncatula.SRC was funded by a post-doc grant (SFRH/BPD/26496/2006) supported by the Portuguese Foundation for Science and Technology (FCT)

Pre-Service Science Teachers’ Scientific Reasoning Competencies: Analysing the Impact of Contributing Factors

Scientific reasoning competencies (SRC) are one part of science teachers’ professional competencies. This study examines the contribution of three factors to the development of pre-service science teachers’ SRC: the amount of science education classes, the amount of science classes and the pre-service science teachers’ age. The factors amount of science education classes and amount of science classes have been operationalised in terms of ECTS credit points. N = 438 pre-service science teachers from six universities in Germany, Chile and Canada voluntarily and anonymously responded to an established multiple-choice instrument for assessing SRC, which has been developed by the authors and is available in German, Spanish and English. Multiple linear regression analyses show that the included factors explain a proportion of about 9% of the pre-service science teachers’ SRC. The factor amount of science classes is the only significant predictor and can be seen as an indicator of learning science content knowledge. These findings support the assumption of science content knowledge being a prerequisite for developing pre-service science teachers’ SRC

Proceedings in Marine Biology

“Proceedings in Marine Biology” is an international journal publishing original research by graduate students on all aspects of marine biology. Subjects covered include: ecological surveys and population studies of oceanic, coastal and shore communities; physiology and experimental biology; taxonomy, morphology and life history of marine animals and plants. Papers are also published on techniques em - ployed at sea for sampling, recording, capture and observation of marine organisms.Zeitschrift zur Kursabschlussreise der Humboldt-Universität zu Berlin (Deutschland) im Bereich Elektronenmikroskopie.Peer Reviewe

Zum Umdrehverhalten der Asteroidea am Beispiel von Asterias rubens, Marthasterias glacialis und Crossaster papposus

Asteroidea are pentaradial echinoderms with an oral-aboral body axis. The madreporite, situated in the first interradius is connected to the axial complex, the stone canal, and the hydrocoelic canals. Because of the physiological importance of this system we hypothesized that the turning behaviour of the sea stars Asterias rubens, Marthasterias glacialis, and Crossaster papposus is not randomly distributed across the different arms but that a relation to the first interradius exists. Using video analysis, we could document a complex succession of the arms, which can differ within a species and moreover, within an individual. At the beginning of each turning move, two radials laying next to each other get in contact with the substratum. The succession of the arms of C. papposus is more variable compared to the studied Asteriidae. Often the “tulip-form” is realized in C. papposus, where all radials are turned towards each other before the onset of the turning movement proper. For A. rubens and M. glacialis there was no significant aberration from a random pattern regarding the first interradius. In contrast, C. papposus turned significantly more often over the quarter containing the madreporite and first interradius than could be expected in a random distribution. This correlates with the more complex behaviour in this species and the occurrence of the “tulip-form”. We discuss the possibilities that differences in regeneration ability or sensory integration might be responsible for this divergence.Asteroidea sind pentaradiale Stachelhäuter mit einer oral-aboralen Körperachse. Der Madreporit, der sich im ersten Interradius befindet, ist mit dem axialen Komplex, dem Steinkanal und den hydrocoelischen Kanälen verbunden. Aufgrund der physiologischen Bedeutung dieses Systems stellten wir die Hypothese auf, dass das Drehverhalten der Seesterne Asterias rubens, Marthasterias glacialis und Crossaster paposus nicht zufällig auf die verschiedenen Arme verteilt ist, sondern eine Beziehung zum ersten Interradius besteht. Mittels Videoanalyse konnten wir eine komplexe Abfolge der Arme dokumentieren, die sich innerhalb einer Art und darüber hinaus innerhalb eines Individuums unterscheiden kann. Zu Beginn jeder Wendebewegung kommen zwei nebeneinander liegende Radials mit dem Untergrund in Kontakt. Die Abfolge der Arme von C. papposus ist im Vergleich zu den untersuchten Asteriidae variabler. Bei C. papposus wird oft die „Tulpenform“ realisiert, bei der alle Radials vor Beginn der eigentlichen Drehbewegung aufeinander zugedreht sind. Für A. rubens und M. glacialis gab es keine signifikante Abweichung von einem zufälligen Muster bezüglich des ersten Interradius. Im Gegensatz dazu drehte sich C. papposus in dem Viertel, das den Madreporit und den ersten Interradius enthält, deutlich häufiger, als in einer zufälligen Verteilung zu erwarten war. Dies korreliert mit dem komplexeren Verhalten dieser Art und dem Vorkommen der „Tulpenform“. Wir diskutieren die Möglichkeiten, dass Unterschiede in der Regenerationsfähigkeit oder der sensorischen Integration für diese Divergenz verantwortlich sein könnten.Peer Reviewe

Functions of Flavonoids in Plant–Nematode Interactions

Most land plants can become infected by plant parasitic nematodes in the field. Plant parasitic nematodes can be free-living or endoparasitic, and they usually infect plant roots. Most damaging are endoparasites, which form feeding sites inside plant roots that damage the root system and redirect nutrients towards the parasite. This process involves developmental changes to the root in parallel with the induction of defense responses. Plant flavonoids are secondary metabolites that have roles in both root development and plant defense responses against a range of microorganisms. Here, we review our current knowledge of the roles of flavonoids in the interactions between plants and plant parasitic nematodes. Flavonoids are induced during nematode infection in plant roots, and more highly so in resistant compared with susceptible plant cultivars, but many of their functions remain unclear. Flavonoids have been shown to alter feeding site development to some extent, but so far have not been found to be essential for root–parasite interactions. However, they likely contribute to chemotactic attraction or repulsion of nematodes towards or away from roots and might help in the general plant defense against nematodes. Certain flavonoids have also been associated with functions in nematode reproduction, although the mechanism remains unknown. Much remains to be examined in this area, especially under field conditions

An evaluation of a scientific reasoning test for pre-service biology teachers: Using relations-to-other-variables as source of validity evidence

Im Projekt ValiDiS wird die Interpretation des Testwerts für den Multiple-Choice Ko-WADiS-Test zum wissenschaftlichen Denken unter Berücksichtigung des Validitätskriteriums relations-to-other-variables überprüft. Zur Untersuchung des empirischen Zusammenhangs des Testwerts mit den Konstrukten schlussfolgerndes Denken (verbale, numerische, figurale Intelligenz; I-S-T 2000 R) und komplexes Problemlösen (systematic exploration, system knowledge, control performance; Genetics Lab-Test) wurden etablierte Messinstrumente bei Biologie-Lehramtsstudierenden (N = 232) eingesetzt. Es zeigen sich positive, überwiegend signifikante Korrelationen mit mittleren Effekten, was die Annahme, dass es sich um distinkte Konstrukte mit verbindenden Kernfacetten handelt, stützt. Darüber hinaus besteht ein positiver Zusammenhang zwischen den Testwerten und der Abiturgesamtnote. Der Beitrag diskutiert die Befunde als Evidenz für eine valide Interpretation des Ko-WADiS-Testwerts. (DIPF/Orig.)For the ValiDiS project, the interpretation of the test score of a multiple-choice test for scientific reasoning (the Ko-WADiS-test) is examined, taking into account the validity criterion relations-to-other-variables. In order to investigate the empirical relation of the test score with deductive reasoning (verbal, numerical, figurative intelligence, I-S-T 2000 R) and complex problem solving (systematic exploration, system knowledge, control performance, Genetics Lab-test), established assessment instruments were used to obtain test scores of pre-service science teachers (N = 232). There are positive, mostly significant correlations with medium effects, which supports the assumption that they are distinct constructs with linking facets. In addition, there is a positive correlation between the test score and the final grade. In this contribution, the findings are discussed as evidence for a valid test score interpretation of the Ko-WADiS-test. (DIPF/Orig.