Biology subjects

Kraus, J. M.

Publications and source records attributed to Kraus, J. M..

6 recordsLinked to original sources

bioRxiv2026

The molecular architecture of the Arabidopsis callose synthase complex

ABSTRACTCallose synthase is responsible for the targeted deposition of the {beta}-1,3-glucan polymer, callose which underlines essential plant developmental processes, including cell division, pathogen defense or cell-cell communication. The architecture of the callose synthase complex (CALSC) as well as the molecular mechanisms of callose synthesis remain unknown. Here we report an integrative characterisation of the Arabidopsis CALS complex, with the most enriched subunits, CALS1, CALS2 and CALS3, forming its core. Structurally, CALSC assembles into a trimer, requiring the plant-specific Bag domain to mediate inter-subunit associations. The biological importance of CALSC assembly is highlighted by the simultaneous loss of CALS1 and CALS3, which abolishes plasmodesmal callose deposition and affects symplastic transport. Site-directed mutagenesis and molecular dynamics simulations depict the topology of the CALS1 active site in detail, including the components of the enzymatic reaction. We pinpoint the translocating tunnel through which the nascent glucan is delivered and mechanistically confirm the role of transmembrane helix 8 in regulating glucan export. Our work provides unprecedented insight into the molecular architecture of the CALSC and the distinct changes from maturation to activity at the plasma membrane, while showcasing the mechanisms involved in callose synthesis at the molecular level.

plant biology↗

bioRxiv2026

Novel repressors of cambium activity in Arabidopsis

Wood is the greatest reservoir of terrestrial biomass and an essential carbon sink. Formed of xylem, it is derived from the cambium, a meristematic zone within plant stems from which phloem also forms. In Arabidopsis, cell division within the cambium is promoted by three major factors: auxin, cytokinin, and the TDIF-PXY ligand-receptor pair. Meristems and other stem cell populations are typically regulated by a balance between cell division-promoting factors and those that repress cell division to control meristem size, however few factors with cambium-repressing activity are known. Here we combined transcriptomics and transcriptional network analysis, which led to identification of related homeodomain zinc-finger transcription factors, ATHB23, ATHB30, and ATHB34, that repress cambium activity. These factors inhibit cambium activity by directly binding of promoters from a subset of auxin, cytokinin and TDIF-PXY transcriptional target genes, resulting in attenuation of their transcription. Our findings thus reveal a new mechanism underpinning balanced cambium activity.

plant biology↗

bioRxiv2025

Pancreatic cancer patient-derived organoids capture therapy response and tumor evolution

Patient-derived organoids (PDOs) reflect parental tumor features and may represent promising avatars for prognosticating drug response. Here, we recruited 169 patients with pancreatic cancer (PC) and established a living biobank including 83 pharmacotyped PDOs isolated from primary and metastatic, treatment-naive and pretreated PCs. In a core facility setting, the pharmacotyping success rate was 61.5%, with an unmet turnaround time of 32 days. Forty-six patients who underwent a total of 94 therapeutic lines were analyzed, resulting in a pharmacotyping-patient response matching rate of 73.4%. Sensitivity, specificity, positive and negative predictive values were 85.0%, 64.8%, 64.2%, and 85.4%, respectively. Tracing clonal evolution in longitudinal biopsies uncovered therapy-induced genetic alterations and single-nucleus multiomics identified transcriptomic and epigenetic changes associated with abnormal FGF signaling during treatment in one particular tracked study case. Our findings highlight the potential of PDOs as robust tools for drug response prediction and patient modeling to advance functional precision medicine.

cancer biology↗

bioRxiv2024

The structural scaffold of the TPLATE complex deforms the membrane during plant endocytosis

Summary paragraphEukaryotic cells maintain homeostasis of their outer membrane by controlled internalization of lipid and protein constituents via endocytosis1. Endocytosis is evolutionary conserved and utilizes similar structural folds. How these structural folds are combined into proteins and protein complexes however differs between eukaryotic kingdoms2. The TPLATE complex in plants is an evolutionary ancient protein module that combines several endocytic folds into a single octameric protein complex3-5. Its molecular architecture, lipid-nucleated condensate formation, and its requirement for clathrin cage curvature revealed its function in endocytosis initiation in plants6-8. Mechanistic understanding of how this complex drives membrane deformation during plant endocytosis is, however, lacking. Here, we used an integrative structural approach to obtain a precise molecular structure of the TPLATE complex. In addition, our approach allowed visualizing the structural flexibility that hallmarks this enigmatic complex. We prove that the intrinsic structural flexibility is required for its functionality and membrane recruitment. The membrane binding interface consists of several domains with differential lipid preferences. Finally, we show that the crescent shape of the structured part of the complex is sufficient for membrane curvature generation. Our mechanistic insight answers the long-standing question of how plants execute endocytosis without cytoskeletal-based force generation.

plant biology↗

bioRxiv2022

Non-aging despite high mutation rate - genomic insights into the evolution of Hydra

Hydra is a genus of freshwater polyps with remarkable regeneration abilities and a non-senescent phenotype under laboratory conditions. Thus, this animal is particularly interesting for aging research. Here, we gained insights into Hydras recent genetic evolution by genome sequencing of single cells and whole individuals. Despite its extreme longevity, Hydra does not show a lower somatic mutation rate than humans or mice. While we identify biological processes that have evolved under positive selection in animals kept in optimal laboratory conditions for decades, we found no signs of strong negative selection during this tiny evolutionary window. Interestingly, we observe the opposite pattern for the preceding evolution in the wild over a longer time period. Moreover, we found evidence that Hydra evolution in captivity was accompanied and potentially accelerated by loss of heterozygosity. Processes under positive selection in captive animals include pathways associated with Hydras simple nervous system, its nucleic acid metabolic process, cell migration, and hydrolase activity. Genes associated with organ regeneration, regulation of mRNA splicing, histone ubiquitination, and mitochondrial fusion were identified as highly conserved in the wild. Remarkably, several of the processes under strongest selection are closely related to those considered essential for the exapted, i. e. not brought about by natural selection, feature: Hydras non-aging.

evolutionary biology↗

bioRxiv2020

Dynamic characteristics rather than static hubs are important in biological networks

Biological processes are rarely a consequence of single protein interactions but rather of complex regulatory networks. However, interaction graphs cannot adequately capture temporal changes. Among models that investigate dynamics, Boolean network models can approximate simple features of interaction graphs integrating also dynamics. Nevertheless, dynamic analyses are time-consuming and with growing number of nodes may become infeasible. Therefore, we set up a method to identify minimal sets of nodes able to determine network dynamics. This approach is able to depict dynamics without calculating exhaustively the complete network dynamics. Applying it to a variety of biological networks, we identified small sets of nodes sufficient to determine the dynamic behavior of the whole system. Further characterization of these sets showed that the majority of dynamic decision-makers were not static hubs. Our work suggests a paradigm shift unraveling a new class of nodes different from static hubs and able to determine network dynamics.

bioinformatics↗