Forschende berichten in der Fachzeitschrift „Science“ über Amphibien mit ähnlich komplexen Brutpflegemechanismen wie Säugetiere.
Stuttgart, 07.03.2024. Elterliche Fürsorge für den Nachwuchs ist weit verbreitet im Tierreich und ist ein wesentlicher Bestandteil der Reproduktion, der Fortpflanzung und der Entwicklung eines Organismus. Ein internationales Team von Wissenschaftler*innen aus Brasilien, den USA und Deutschland, darunter PD Dr. Alexander Kupfer, Kurator für Amphibien und Reptilien am Naturkundemuseum Stuttgart, haben erstmals erforscht, wie eierlegende Schleichenlurchweibchen ihren Nachwuchs erfolgreich im Nest aufziehen.
Schleichenlurche gelten als eine der am wenigsten bekannten Wirbeltiergruppen und gehören zu den Amphibien. Das Forschungsteam fand heraus, dass die Weibchen von eierlegenden Schleichenlurchen, wie der Art Siphonops annulatus, eine ähnlich fettreiche Milch an ihre Jungen im Nest abgeben, wie beispielsweise eierlegende Säugetiere es tun. Diese neue Entdeckung zeigt die Komplexität der Evolution von Fortpflanzungsstrategien bei Wirbeltieren und erweitert das Wissen über die Brutpflege und Kommunikation bei den Schleichenlurchen. Die Forschungsergebnisse wurden in der renommierten Fachzeitschrift „Science“ veröffentlicht.
Bei den meisten Wirbeltieren ist der Dotter in der Regel die einzige Form der Nahrung,
die das Weibchen für den heranwachsenden Embryo bereitstellt. Die Wissenschaftler*innen konnten beobachten, dass die Jungen der Art Siphonops annulatus über zwei Monate lang Milch zu sich nahmen, die scheinbar als Reaktion auf taktile und akustische Stimulation durch die mütterliche Kloake abgesondert wird. Die verfütterte Milch besteht hauptsächlich aus Fetten und Kohlenhydraten und wird in den Drüsen der Eileiter des Weibchens produziert.
„Wir haben durch unsere Untersuchungen bei den Schleichenlurchen nun ein Wirbeltiersystem bei Amphiben entdeckt, das ähnlich umfassende Brutpflegemechanismen entwickelt hat, wie bei den Säugetieren. Dazu gehört die Produktion von fettreicher Muttermilch und die Milchabgabe an die Jungen im Nest, die sogenannte Laktation. Das verrät uns viel über die Evolution und die Fortpflanzungsstrategien dieser immer noch wenig bekannten Wirbeltierordnung“, so Dr. Alexander Kupfer, Zoologe am Naturkundemuseum Stuttgart.
Schleichenlurche sind fußlose, schlangenförmige Amphibien, die in den tropischen Regionen der Erde verbreitet sind. Alle Schleichenlurche betreiben Brutpflege. Die Weibchen des brasilianischen Schleichenlurchs Siphonops annulatus legen Eier und ziehen ihre Schlüpflinge im Nest neben ihrer eigenen Haut als Futter auch mit fettreicher „Milch“ auf. Die elterliche Brutfürsorge ist daher sehr ähnlich der von eierlegenden Säugetieren, wie den Schnabeligeln und den Schnabeltieren.

Originalpublikation: Pedro L. Mailho-Fontana, Marta M. Antoniazzi, Guilherme R. Coelho, Daniel C. Pimenta, Lígia P. Fernandes, Alexander Kupfer, Edmund D. Brodie Jr. & Carlos Jared (2024). Milk provisioning in oviparous caecilian amphibians. Science 383: 1092-1095. DOI: 10.1126/science.adi5379 Veröffentlichungsdatum: 08.03.2024

Nan Wang, Zhidan Wang, Sofia Tzourtzou, Xu Wang, Xiuli Bi, Julia Leimeister, Linhao Xu, Takuya Sakamoto, Sachihiro Matsunaga, Andreas Schaller, Hua Jiang & Chang Liu

Nature Plants (2023)

https://doi.org/10.1038/s41477-023-01457-2

DOI: 10.1038/s41477-023-01457-2

The nuclear lamina is a complex network of nuclear lamins and lamin-associated nuclear membrane proteins, which scaffold the nucleus to maintain structural integrity. In Arabidopsis thaliana, nuclear matrix constituent proteins (NMCPs) are essential components of the nuclear lamina and are required to maintain the structural integrity of the nucleus and specific perinuclear chromatin anchoring. At the nuclear periphery, suppressed chromatin overlapping with repetitive sequences and inactive protein-coding genes are enriched. At a chromosomal level, plant chromatin organization in interphase nuclei is flexible and responds to various developmental cues and environmental stimuli. On the basis of these observations in Arabidopsis, and given the role of NMCP genes (CRWN1 and CRWN4) in organizing chromatin positioning at the nuclear periphery, one can expect considerable changes in chromatin–nuclear lamina interactions when the global chromatin organization patterns are being altered in plants. Here we report the highly flexible nature of the plant nuclear lamina, which disassembles substantially under various stress conditions. Focusing on heat stress, we reveal that chromatin domains, initially tethered to the nuclear envelope, remain largely associated with CRWN1 and become scattered in the inner nuclear space. By investigating the three-dimensional chromatin contact network, we further reveal that CRWN1 proteins play a structural role in shaping the changes in genome folding under heat stress. Also, CRWN1 acts as a negative transcriptional coregulator to modulate the shift of the plant transcriptome profile in response to heat stress.

Jan-Louis Hau, Susann Kaltwasser, Valentin Muras, Marco S. Casutt, Georg Vohl, Björn Claußen, Wojtek Steffen, Alexander Leitner, Eckhard Bill, George E. Cutsail 3rd, Serena DeBeer, Janet Vonck, Julia Steuber, Günter Fritz

Nature Structural & Molecular Biology (2023)

https://www.nature.com/articles/s41594-023-01099-0

DOI: 10.1038/s41594-023-01099-0

Energy conversion is a central characteristic of life. All organisms derive energy from redox reactions and convert this into electric energy by building up an ion gradient across the membrane. This electric energy is converted back into chemical energy by ATP synthetases. These energy conversion steps are realized in the cells by large membrane-bound multi-protein complexes. The molecular mechanism, how these complexes convert the energy, is still poorly understood. In mitochondria or many bacteria, NADH is oxidized to drive ion translocation and build up such an electrochemical gradient. Many pathogenic bacteria like Vibrio cholerae use a sodium-pumping NADH:quinone oxidoreductase (Na+-NQR) to generate a sodium gradient. Our studies on the Na+-NQR complex had revealed the first three-dimensional structural information and show now that ion pumping is driven by large conformational changes. New structural information by cryo-EM and functional analysis revealed that the transfer of the electrons, which have been stripped of NADH, drive concerted movements in the protein complex. These movements are required to shuttle the electrons to ubiquinone and at the same time transport Na+ across the membrane.

Jekatarina Truskina, Stefanie Brück, Annick Stintzi, Sophy Boeuf, Satoshi Fujita, Niko Geldner, Andreas Schaller, Gwyneth C. Ingram

Proc. Natl. Acad. Sci. USA (2022) Vol. 119 (16), e2201195119

https://www.pnas.org/doi/10.1073/pnas.2201446119

DOI: 10.1073/pnas.2201446119

Pollen viability depends on a tough external barrier called the pollen wall. Pollen wall components are produced by tapetum cells, which surround developing pollen grains within the anther. Precise coordination of tapetum activity with pollen grain development is required to ensure effective pollen wall formation. Here, we reveal that this is achieved through a multidirectional dialogue involving three distinct cell types. We show that peptide precursors from the tapetum are activated by proteases produced stage specifically in developing pollen grains. Unexpectedly, we found that activated peptides are perceived not in the tapetum, but in the middle layer, which encloses the developing tapetum and pollen grains, revealing an unsuspected role for this enigmatic cell layer in the control of tapetum development.

Marie Pollmann, Logan D. Moore, Elena Krimmer, Paul D’Alvise, Martin Hasselmann, Steve J. Perlman, Matthew J. Ballinger, Johannes L.M. Steidle, and Yuval Gottlieb

iScience 25, 104335, May 20, 2022

https://www.sciencedirect.com/science/article/pii/S258900422200606X

DOI: https://doi.org/10.1016/j.isci. 10.1016/j.isci. 2022.10433

Cytoplasmic incompatibility (CI) is a form of reproductive manipulation caused by maternally inherited endosymbionts infecting arthropods, like Wolbachia, whereby matings between infected males and uninfected females produce few or no offspring. We report the discovery of a new CI symbiont, a strain of Spiroplasma causing CI in the parasitoid wasp Lariophagus distinguendus. Its extracellular occurrence enabled us to establish CI in uninfected adult in- sects by transferring Spiroplasma-infected hemolymph. We sequenced the CI-Spiroplasma genome and did not find any homologues of any of the cif genes discovered to cause CI in Wolbachia, suggesting independent evolution of CI. Instead, the genome contains other potential CI-causing candidate genes, such as homologues of high-mobility group (HMG) box proteins that are crucial in eukaryotic development but rare in bacterial genomes. Spiroplasma’s extra- cellular nature and broad host range encompassing medically and agriculturally important arthropods make it a promising tool to study CI and its applications.

Stefanie Royek, Martin Bayer, Jens Pfannstiel, Jürgen Pleiss, Gwyneth Ingram, Annick Stintzi, Andreas Schaller

Proc. Natl. Acad. Sci. USA (2022) Vol. 119 (16), e2201195119

https://www.pnas.org/doi/10.1073/pnas.2201195119

DOI: 10.1073/pnas.2201195119

Most peptide hormones and growth factors are matured from larger inactive precursor proteins by proteolytic processing and further post-translational modification. Whether or how post-translational modifications contribute to peptide bioactivity is still largely unknown. We address this question here for TWS1 (Twisted Seed 1), a peptide regulator of embryonic cuticle formation in Arabidopsis thaliana. Using synthetic peptides encompassing the N- and C-terminal processing sites and the recombinant TWS1 precursor as substrates, we show that the precursor is cleaved by the subtilase SBT1.8 at both the N- and the C-terminus of TWS1. Recognition and correct processing at the N-terminal site depended on sulfation of an adjacent tyrosine residue. Arginine 302 of SBT1.8 was found to be required for sulfo-tyrosine binding and for accurate processing of the TWS1 precursor. The data reveal a critical role for post-translational modification, here tyrosine sulfation of a plant peptide hormone precursor, in mediating processing specificity and peptide maturation.

Pawel R. Laskowski, Kristyna Pluhackova, Maximilian Haase, Brian M. Lang, Gisela Nagler, Andreas Kuhn & Daniel J. Müller

Nature Communications volume 12, Article number: 7082 (2021

https://doi.org/10.1038/s41467-021-27315-3

Membrane insertases are present in all organisms and catalyse the insertion of newly synthesized proteins into the membrane bilayer. The bacterial insertase YidC spans the inner membrane 6 times forming a hydrophilic groove in the bilayer which hosts the substrate periplasmic domain prior its translocation. In the cytoplasm a two-helix domain is present in all the homologues that might function in the recognition of devoted substrate proteins. Here, we have investigated the role of this helical hairpin using a deletion and single residue mutations with a model substrate, the Pf3 coat protein.

Fluorescently labelled Pf3 protein showed insertion into the YidC proteoliposomes whereas the mutants were severely affected already for the binding to YidC. To study this in more detail the C­-terminus of the Pf3 proteins was linked to a cantilever of an AFM and tested for binding to YidC that had been reconstituted into proteoliposomes. Using single molecule force spectroscopy we observed that all substrates interact with YidC within 2 ms. Whereas the wildtype strengthens its binding to YidC after 4 ms the mutants did not, suggesting that the electrostatic binding to the helical hairpin and groove is involved in the second substrate binding step.

Molecular dynamic simulations were then applied to investigate the conformational variability and kinetic stability of the inserting Pf3 protein with the helical hairpin and the hydrophilic groove of YidC. These data suggest that the negatively charged residues in the N-terminal part of Pf3 are electrostatically interacting with the helical hairpin and are then guided to the-hydrophilic groove prior their membrane translocation.

Doll, N.M., Royek, S., Fujita, S., Okuda, S., Chamot, S., Stintzi, A., Widiez, T., Hothorn, M., Schaller, A., Geldner, N., Ingram, G.

Science (2020) Vol 367, pp 431-435

F1000Prime Recommendation: very good, 04 Feb 2020; 10.3410/f.737255121.793570439

Faculty Opinions recommendation: exceptional, June 22; 10.3410/f.737255121.793575412

https://science.sciencemag.org/content/367/6476/431

DOI: 10.1126/science.aaz4131

In a plant seed, the embryo lies dormant surrounded by nutritive endosperm while awaiting suitable conditions to germinate. A hydrophobic cuticle around the embryo protects it from catastrophic water loss during the early days of growth. Doll et al. identified a back-and-forth signaling pathway that ensures an intact cuticle. The precursor of a signaling peptide is made in the embryo and transferred to the endosperm, where it is processed into its active form by the subtilisin-like protease ALE1. The activated peptide diffuses back into the embryo to activate receptor-like kinases that drive cuticle development. Serve and return continues until all leaks in the cuticle are filled in and the peptide can no longer cross the barrier.

Stührwohldt, N., Scholl, S., Lang, L., Katzenberger, J., Schumacher, K., Schaller A.

eLife (2020) Vol. 9:e55580

https://elifesciences.org/articles/55580

doi: 10.7554/eLife.55580

Post-translationally modified peptides are involved in many aspects of plant growth and development. The maturation of these peptides from their larger precursors is still poorly understood. We show here that the biogenesis of CLEL6 and CLEL9 peptides in Arabidopsis thaliana requires a series of processing events in consecutive compartments of the secretory pathway. Following cleavage of the signal peptide upon entry into the endoplasmic reticulum (ER), the peptide precursors are processed in the cis-Golgi by the subtilase SBT6.1. SBT6.1-mediated cleavage within the variable domain allows for continued passage of the partially processed precursors through the secretory pathway, and for subsequent post-translational modifications including tyrosine sulfation and proline hydroxylation within, and proteolytic maturation after exit from the Golgi. Activation in post-Golgi compartments depends on the N-terminal aspartate of the mature peptides. Our work highlights the complexity of post-translational precursor maturation allowing for stringent control of peptide biogenesis.

Roman T. Kellenberger, Kelsey J. R. P. Byers, Rita M. De Brito Francisco, Yannick M. Staedler, Amy M. LaFountain, Jürg Schönenberger, Florian P. Schiestl & Philipp M. Schlüter

Nature Communications (2019) Vol. 10,  article number: 63

https://doi.org/10.1038/s41467-018-07936-x

https://facultyopinions.com/prime/734831211

Maintenance of polymorphism by overdominance (heterozygote advantage) is a fundamental concept in evolutionary biology. In most examples known in nature, overdominance is a result of homozygotes suffering from deleterious effects. Here we show that overdominance maintains a non-deleterious polymorphism with black, red and white floral morphs in the Alpine orchid Gymnadenia rhellicani. Phenotypic, metabolomic and transcriptomic analyses reveal that the morphs differ solely in cyanidin pigments, which are linked to differential expression of an anthocyanidin synthase (ANS) gene. This expression difference is caused by a premature stop codon in an ANS-regulating R2R3-MYB transcription factor, which is heterozygous in the red colour morph. Furthermore, field observations show that bee and fly pollinators have opposite colour preferences; this results in higher fitness (seed set) of the heterozygous morph without deleterious effects in either homozygous morph. Together, these findings demonstrate that genuine overdominance exists in nature.

Schardon., K., Hohl, M., Graff, L., Schulze, W., Pfannstiel, J., Stintzi, A., Schaller, A.

Science (2016) Vol. 354, pp 1594-1597

https://science.sciencemag.org/content/354/6319/1594

DOI: 10.1126/science.aai8550

F1000Prime Recommendation

A flower that has gone to seed will drop its petals in a regulated process called abscission. Schardon et al. analyzed the production of the peptide hormone that regulates floral organ abscission in the model plant Arabidopsis thaliana. Tissue-specific expression of proteinase inhibitors was used as a tool to overcome functional redundancy and allowed identification of the subtilisin-like proteinases that act as prohormone convertases required for peptide hormone production in plants.

Gasper, R., Effenberger, I., Kolesinski, P., Terlecka, B., Hofmann, E., Schaller, A.

Plant Physiol. (2016) Vol.172, pp 2165–2175

http://www.plantphysiol.org/content/172/4/2165

DOI: 10.1104/pp.16.01281

Dirigent proteins impart stereoselectivity to phenoxy radical coupling reactions in plants. They play an essential role in the biosynthesis of biologically active natural products that act as chemical defense against insect pests and pathogens. The committed step of lignan biosynthesis is the enantioselective coupling and subsequent cyclization of two coniferyl alcohol radicals to pinoresinol. The reaction is controlled by dirigent proteins, which, depending on the species and protein, direct the reaction to either (+)- or (−)-pinoresinol. We present the crystal structure of the (−)-pinoresinol forming DIRIGENT PROTEIN6 (AtDIR6) from Arabidopsis. The structure shows AtDIR6 as an eight-stranded antiparallel β-barrel that forms a trimer with spatially well-separated cavities for substrate binding. Two substrate radicals bind to each of the DIR monomers. With the aromatic rings fixed in the two pockets, the propionyl side chains face each other for radical-radical coupling, and stereoselectivity is determined by the exact positioning of the side chains. Extensive mutational analysis supports a previously unrecognized function for DIRs in catalyzing the cyclization of the bis-quinone methide reaction intermediate to yield (+)- or (−)-pinoresinol.

Effenberger, I., Zhang, B., Li, L., Wang, Q., Liu, Y., Klaiber, I., Pfannstiel, J., Wang, Q., Schaller, A.

 Angew. Chem. Int. Ed. (2015) Vol 54, pp 14660–14663

https://onlinelibrary.wiley.com/doi/full/10.1002/anie.201507543

DOI: 10.1002/anie.201507543

Gossypol is a defense compound in cotton plants for protection against insect pests and pathogens. Gossypol biosynthesis involves the oxidative coupling of hemigossypol and results in two atropisomers owing to hindered rotation around the central binaphthyl bond. (+)‐Gossypol predominates in vivo, thus suggesting stereochemically controlled biosynthesis. Aiming to identify the factors mediating stereoselectivity, we discovered a dirigent protein from Gossypium hirsutum (GhDIR4) that confers atropselectivity to the coupling of hemigossypol in presence of laccase and O2 as an oxidizing agent. (+)‐Gossypol was obtained in greater than 80 % enantiomeric excess compared to racemic gossypol in the absence of GhDIR4. The identification of GhDIR4 highlights a broader role for DIRs in plant secondary metabolism and may eventually lead to the development of DIRs as tools for the synthesis of axially chiral binaphthyls.