Biology subjects

Ortmann, S.

Publications and source records attributed to Ortmann, S..

5 recordsLinked to original sources

bioRxiv2026

Myosin-Driven Nuclear Movement Generates Stromules in Arabidopsis thaliana

Plastids form stroma-filled tubular extensions, termed stromules, that are implicated in inter-organellar communication. In pathogen-challenged Nicotiana benthamiana, stromule formation is driven by kinesins acting along microtubules. However, whether this mechanism also operates in unstressed plants or in other species remains unknown. Using systematic genetic analysis of all class XI myosin genes and quantitative time-lapse imaging in Arabidopsis (Arabidopsis thaliana), we show that basal stromule formation is predominantly myosin dependent through two distinct mechanisms. Myosin XI-I generates most stromules by driving oscillatory nuclear movement that mechanically pulls stromules from stationary plastids within the approx. 8m wide stromule-promoting zone. Myosins XI-K, XI-1, and XI-2 additionally drive a movement-independent, nucleus-associated stromule subpopulation within the same zone, establishing two mechanistically distinct pathways. We propose that movement-coupled stromules function as dynamic tethers maintaining plastid-nucleus proximity during nuclear oscillations, while movement-independent stromules expand the plastid membrane area within the perinuclear space, increasing the potential contact surface with the nucleus and surrounding environment. Together, both populations are proposed to enhance signal and metabolite exchange at the plastid-nucleus interface. These findings indicate that stromule biogenesis is both mechanistically and functionally context dependent, challenging the universality of the kinesin-microtubule model across plant species and physiological states.

plant biology↗

bioRxiv2026

Movement strategies reveal the success of mammals in urban areas

Various hypotheses have been proposed to explain why some species persist or even flourish in urban areas. Yet, despite its central role in determining when and where animals encounter resources, disturbance, and risk, movement behaviour remains an overlooked mechanism of urban success. In urban areas, human activities are strongly periodic, i.e. predictable in space and time. This may favour species able to adjust their behaviour to predictable cycles of resources and risks in space and time. Here, we tested this hypothesis and tracked movement behaviour along an urbanisation gradient in three mammal species with different urban success: red fox (Vulpes vulpes), an urban dweller; raccoon (Procyon lotor), an invasive urban dweller; and wild boar (Sus scrofa), an urban utiliser. We analysed periodicity in movement behaviour and investigated whether increasing urbanisation is associated with periodic reorganisation of activity timing, space use, and further analysed alterations in habitat selection along the urbanisation gradient. Our results show that foxes aligned their movement behaviour with human activity, having stronger day-night contrasts and more repeatable space use than their rural counterparts. Urban raccoons showed a contrasting strategy; they were more active during the day, without changes in their movement routines under increasing urbanisation, suggesting a flexible strategy that explains their urban success. In contrast, wild boars reduced routine movement behaviours with increasing urbanisation, consistent with their occurrence in less predictable suburban environments and avoidance of city centres. In summary, our results suggest that movement behaviour may be a key mechanism enabling animals to persist in cities, revealing distinct behavioural strategies for coping with urban environments.

ecology↗

bioRxiv2023

A conserved microtubule-binding region in Xanthomonas XopL is indispensable for induced plant cell death reactions.

Pathogenic Xanthomonas bacteria cause disease on more than 400 plant species. These Gram-negative bacteria utilize the type III secretion system to inject type III effector proteins (T3Es) directly into the plant cell cytosol where they can manipulate plant pathways to promote virulence. The host range of a given Xanthomonas species is limited, and T3E repertoires are specialized during interactions with specific plant species. Some effectors, however, are retained across most strains, such as Xanthomonas Outer Protein L (XopL). As an ancestral effector, XopL contributes to the virulence of multiple xanthomonads, infecting diverse plant species. XopL homologs harbor a combination of a leucine-rich-repeat (LRR) domain and an XL-box which has E3 ligase activity. Despite similar domain structure there is evidence to suggest that XopL function has diverged, exemplified by the finding that XopLs expressed in plants often display bacterial species-dependent differences in their sub-cellular localization and plant cell death reactions. We found that XopL from X. euvesicatoria (XopLXe) directly associates with plant microtubules (MTs) and causes strong cell death in agroinfection assays in N. benthamiana. Localization of XopLXe homologs from three additional Xanthomonas species, of diverse infection strategy and plant host, revealed that only the distantly related X. campestris pv. campestris harbors a XopL (XopLXcc) that fails to localize to MTs and to cause plant cell death. Comparative sequence analyses of MT-binding XopLs and XopLXcc identified a proline-rich-region (PRR)/-helical region important for MT localization. Functional analyses of XopLXe truncations and amino acid exchanges within the PRR suggest that MT-localized XopL activity is required for plant cell death reactions. This study exemplifies how the study of a T3E within the context of a genus rather than a single species can shed light on how effector localization is linked to biochemical activity. Author summaryXanthomonas Outer Proteins (Xops) are type III effector proteins originating from bacterial plant pathogens of the Xanthomonas genus. Xanthomonas uses a needle-like structure to inject a cocktail of Xops directly into plant cells where they manipulate cellular processes to promote virulence. Previous studies of individual Xops have provided valuable insights into virulence strategies used by Xanthomonas, knowledge that can be exploited to fight plant disease. However, despite rapid progress in the field, there is much about effector activity we still do not understand. Our study focuses on the effector XopL, a protein with E3 ligase activity that is important for Xanthomonas virulence. In this study we expressed XopLs in leaves of the model plant N. benthamiana and found that XopLs from different Xanthomonas species differ in their subcellular localization. XopLs from closely related species associate with the microtubule cytoskeleton and disassemble it, whereas a XopL from a distantly related species did not. This prompted a comparative analysis of these proteins, which showed how microtubule binding is achieved and how it affects the plant response to XopL.

pathology↗

bioRxiv2022

Oral rabies vaccination of dogs - experiences from a field trial in Namibia

Dog-mediated rabies is responsible for tens of thousands of human deaths annually, and in resource-constrained settings, vaccinating dogs to control the disease at source remains challenging. Currently, rabies elimination efforts rely on mass dog vaccination by the parenteral route. To increase the herd immunity, free-roaming and stray dogs need to be specifically addressed in the vaccination campaigns, with oral rabies vaccination (ORV) of dogs being a possible solution. Using a third-generation vaccine and a standardized egg-flavoured bait, bait uptake and vaccination was assessed under field conditions in Namibia. During this trial, both veterinary staff as well as dog owners expressed their appreciation to this approach of vaccination. Of 1,115 dogs offered a bait, 90% (n=1,006, 95%CI:91-94) consumed the bait and 72.9% (n=813, 95%CI:70.2-75.4) of dogs were assessed as being vaccinated, while for (11.7%, n=130, 95%CI:9.9-17.7) the status was recorded as "unkown" and 15.4% (n=172, 95%CI: 13.4-17.7) were considered as being not vaccinated. Smaller dogs and dogs offered a bait with multiple other dogs had significantly higher vaccination rates, while other factors, e.g. sex, confinement status and time had no influence. The favorable results of this first large-scale field trial further support the strategic integration of ORV into dog rabies control programmes. Given the acceptance of the egg-flavored bait under various settings worldwide, ORV of dogs could become a game-changer in countries, where control strategies using parenteral vaccination alone failed to reach sufficient vaccination coverage in the dog population.

microbiology↗

bioRxiv2021

Phenotyping in the era of genomics: MaTrics a digital character matrix to document mammalian phenotypic traits coded numerically

A new and uniquely structured matrix of mammalian phenotypes, MaTrics (Mammalian Traits for Comparative Genomics) is presented in a digital form. By focussing on mammalian species for which genome assemblies are available, MaTrics provides an interface between mammalogy and comparative genomics. MaTrics was developed as part of a project to link phenotypic differences between mammals to differences in their genomes using Forward Genomics. Apart from genomes this approach requires information on homologous phenotypes that are numerically encoded (presence-absence; multistate character coding*) in a matrix. MaTrics provides these data, links them to at least one reference (e.g., literature, photographs, histological sections, CT-scans, or museum specimens) and makes them available in a machine actionable NEXUS-format. By making the data computer readable, MatTrics opens a new way for digitizing collections. Currently, MaTrics covers 147 mammalian species and includes 207 characters referring to structure, morphology, physiology, ecology and ethology. Researching these traits revealed substantial knowledge gaps, highlighting the need for substantial phenotyping efforts in the genomic era. Using the trait information documented in MaTrics, previous Forward Genomics screens identified changes in genes that are associated with various phenotypes, ranging from fully-aquatic lifestyle to dietary specializations. These results motivate the continuous expansion of phenotype information, both by filling research gaps or by adding additional taxa and traits. MaTrics is digitally available online within the data repository Morph{middle dot}D{middle dot}Base (www.morphdbase.de).

zoology↗