Biology subjects

Diehl, A.

Publications and source records attributed to Diehl, A..

9 recordsLinked to original sources

bioRxiv2026

Towards crystal structures of filament forming proteins

Filament-forming proteins such as TasA (Bacillus subtilis) and camelysins CalY1, CalY2 (Bacillus cereus) pose a particular challenge for structural analysis due to their strong tendency to self-association and their polydispersity, which severely limits their ability to crystallize or to be a target for NMR-spectroscopy. To address this, it is necessary to modify the amino acid sequence to prevent filamentation. Engineering a series of N- and C-terminal truncated variants by removing flexible parts is often key to success. N-terminal extensions are also a powerful tool for obtaining crystals of fiber-forming proteins.

biochemistry↗

bioRxiv2025

Fast and Accurate Draft Genome Patching with GPatch

Recent advancements in sequencing technologies have yielded numerous long-read draft genomes, promising to enhance understanding of genomic variation. However, draft genomes are typically highly fragmented, posing challenges for functional genomics. We introduce GPatch, a tool that constructs chromosome-scale pseudoassemblies from fragmented drafts using alignments to a reference assembly. GPatch produces complete, accurate, gap-free assemblies preserving over 95% of nucleotides from human and non-human draft genomes. We show that GPatch pseudoassemblies can be used to construct Hi-C matrices, whereas fragmented draft assemblies cannot. Until complete genome assembly becomes routine, GPatch presents a necessary tool for maximizing the utility of draft genomes. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/655567v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@a8485aorg.highwire.dtl.DTLVardef@262cd9org.highwire.dtl.DTLVardef@4a67f8org.highwire.dtl.DTLVardef@efebc1_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2024

Soft X-ray tomography reveals variations in B.subtilis biofilm structure upon tasA deletion

Bacterial biofilms are complex communities of cells within a self-produced extracellular matrix. They play crucial roles in healthcare, nutrition, agriculture and environmental research, yet an analysis of their elaborate 3D architecture remains challenging. Understanding mechanisms of biofilm formation, particularly the effects of chemical, physical, and genetic influences or modifications, is crucial but requires structural information at subcellular resolution to enable a community-level analysis of biofilms. In this work, we developed a "biofilm-in-capillary" growth method compatible with full-rotation soft X-ray tomography, providing high-resolution 3D imaging of bacterial cells and their surrounding extracellular matrix during biofilm formation, without drying or fixation steps. This approach offers 50 nm isotropic spatial resolution, rapid imaging time, and quantitative native analysis of biofilm structure. We demonstrate the potential of our method using Bacillus subtilis biofilms, detecting coherent alignment and chaining of wild-type cells while they are travelling towards the oxygen-rich capillary tip region. In stark contrast, the genetic knock-out {Delta}tasA shows a loss of cellular orientation, including changes in the extracellular matrix in volume and chemical density. Notably, we show that the addition of TasA protein to a culture of a {Delta}tasA strain restores the extracellular matrix density and leads to a compaction of cell assemblies, yet no chaining is observed as for the wildtype. Our approach to imaging biofilms is scalable and transferable, opening new avenues for examining biofilm structure and function across various species, including mixed biofilms, and observing 3D reorganization in response to genetic and environmental factors.

microbiology↗

bioRxiv2022

On-Ramp: a tool for rapid, multiplexed validation of plasmids using nanopore sequencing

Recombinant plasmid vectors are versatile tools which have facilitated discoveries in molecular biology, genetics, proteomics, and many other fields. As the enzymatic and bacterial processes used to create recombinant DNA can introduce errors, sequence validation is an essential step in plasmid assembly. Sanger sequencing is the current standard for plasmid validation, however this method is limited by an inability to sequence through complex secondary structure and lacks scalability when applied to full-plasmid sequencing of multiple plasmids due to read-length limits. While next-generation sequencing (NGS) does provide full-plasmid sequencing at scale, it is impractical and costly when utilized outside of library-scale validation. Here we present OnRamp (Oxford nanopore-based Rapid Analysis of Multiplexed Plasmids), an alternative method for routine plasmid validation which combines the advantages of NGSs full plasmid coverage and scalability with Sangers affordability and accessibility by leveraging nanopores novel long-read sequencing technology. We include customized wet-lab protocols for plasmid preparation along with a pipeline designed for analysis of read data obtained using these protocols. This analysis pipeline is built into the OnRamp webapp (http://OnRamp.BoyleLab.org), which generates alignments between actual and predicted plasmid sequences, quality scores, and read-level views in a user-friendly manner, precluding the need for programming experience in analyzing nanopore results. Here we describe the OnRamp protocols and pipeline, and demonstrate our ability to obtain full sequences from pooled plasmids while detecting sequence variation even in regions of high secondary structure, at less than half the cost of equivalent Sanger sequencing.

molecular biology↗

bioRxiv2021

Single residue substitution in protamine 1 disrupts sperm genome packaging and embryonic development in mice

Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by passive electrostatics between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues that are conserved within, but not across, species. The functional significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, an alanine substitution (P1 K49A) results in ectopic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin. In vitro, the P1 K49A substitution decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential to ensure reproductive fitness.

biochemistry↗

bioRxiv2021

Two step PCR method to exchange the resistance cassette of a vector

For co-transformation of two plasmids, both have to possess different antibiotic selection markers. If that is not the case, normally the gene of interest (GOI) is subcloned into another vector. Here we introduce a fast and easy method to exchange the antibiotic resistance cassette (ARC) in only two PCR steps. Method SummaryTo shuttle the antibiotic resistance cassette (ARC) from one vector to another, one can amplify the ARC of interest and use the resulting PCR-product as a primer pair for the next amplification step. Simply remove parental DNA template by DpnI digestion, transform PCR product directly in E. coli cells, select transformants on an appropriate agar plate and isolate target vector by plasmid preparation.

molecular biology↗

bioRxiv2020

Co-evolutionary analysis reveals a conserved dual binding interface between extracytoplasmic function (ECF) σ factors and class I anti-σ factors

Extracytoplasmic function {sigma} factors (ECFs) belong to the most abundant signal transduction mechanisms in bacteria. Amongst the diverse regulators of ECF activity, class I anti-{sigma} factors are the most important signal transducers in response to internal and external stress conditions. Despite the conserved secondary structure of the class I anti-{sigma} factor domain (ASDI) that binds and inhibits the ECF under non-inducing conditions, the binding interface between ECFs and ASDIs is surprisingly variable between the published co-crystal structures. In this work, we provide a comprehensive computational analysis of the ASDI protein family and study the different contact themes between ECFs and ASDIs. To this end, we harness the co-evolution of these diverse protein families and predict covarying amino acid residues as likely candidates of an interaction interface. As a result, we find two common binding interfaces linking the first -helix of the ASDI to the DNA binding region in the {sigma}4 domain of the ECF, and the fourth -helix of the ASDI to the RNA polymerase (RNAP) binding region of the {sigma}2 domain. The conservation of these two binding interfaces contrasts with the apparent quaternary structure diversity of the ECF/ASDI complexes, partially explaining the high specificity between cognate ECF and ASDI pairs. Furthermore, we suggest that the dual inhibition of RNAP- and DNA-binding interfaces are likely a universal feature of other ECF anti-{sigma} factors, preventing the formation of non-functional trimeric complexes between {sigma}/anti-{sigma} factors and RNAP or DNA. SignificanceIn the bacterial world, extracytoplasmic function {sigma} factors (ECFs) are the most widespread family of alternative {sigma} factors, mediating many cellular responses to environmental cues, such as stress. This work uses a computational approach to investigate how these {sigma} factors interact with class I anti-{sigma} factors - the most abundant regulators of ECF activity. By comprehensively classifying the anti-{sigma}s into phylogenetic groups and by comparing this phylogeny to the one of the cognate ECFs, the study shows how these protein families have co-evolved to maintain their interaction over evolutionary time. These results shed light on the common contact residues that link ECFs and anti-{sigma}s in different phylogenetic families and set the basis for the rational design of anti-{sigma}s to specifically target certain ECFs. This will help to prevent the cross-talk between heterologous ECF/anti-{sigma} pairs, allowing their use as orthogonal regulators for the construction of genetic circuits in synthetic biology.

bioinformatics↗

bioRxiv2019

MapGL: Inferring evolutionary gain and loss of short genomic sequence features by phylogenetic maximum parsimony.

Comparative genomics studies are growing in number partly because of their unique ability to provide insight into shared and divergent biology between species. Of particular interest is the use of phylogenetic methods to infer the evolutionary history of cis-regulatory sequence features, which contribute strongly to phenotypic divergence and are frequently gained and lost in eutherian genomes. Understanding the mechanisms by which cis-regulatory element turnover generate emergent phenotypes is crucial to our understanding of adaptive evolution. Ancestral reconstruction methods can place species-specific cis-regulatory features in their evolutionary context, thus increasing our understanding of the process of regulatory sequence turnover. However, applying these methods to gain and loss of cis-regulatory features currently requires complex workflows which represent a potential barrier to widespread adoption by a broad scientific community. MapGL simplifies phylogenetic inference of the evolutionary history of short genomic sequence features by combining the necessary steps into a single piece of software with a simple set of inputs and outputs.

genomics↗

bioRxiv2018

A molecular mechanism for salt stress-induced microtubule array formation in Arabidopsis

Microtubules are filamentous structures necessary for cell division, motility and morphology, with dynamics critically regulated by microtubule-associated proteins (MAPs). We outline the molecular mechanism by which the MAP, COMPANION OF CELLULOSE SYNTHASE1 (CC1), controls microtubule bundling and dynamics to sustain plant growth under salt stress. CC1 contains an intrinsically disordered N-terminus that links microtubules at evenly distributed distances through four conserved hydrophobic regions. NMR analyses revealed that two neighboring residues in the first hydrophobic binding motif are crucial for the microtubule interaction, which we confirmed through live cell analyses. The microtubule-binding mechanism of CC1 is remarkably similar to that of the prominent neuropathology-related protein Tau, indicating evolutionary convergence of MAP functions across animal and plant cells.

cell biology↗