Biology subjects

Leach, A. G.

Publications and source records attributed to Leach, A. G..

5 recordsLinked to original sources

bioRxiv2025

High-throughput discovery of a dearomative cycloaddition enables dual photochemical-photophysical perturbative probing of protein function

Proteins exist in multiple conformations or states, often associated with different functional capacities. The ability to selectively identify and study these states is crucial for understanding the dynamic nature of proteins and their roles in cellular processes, yet can be currently limited by the artefacts of existing molecular labels and the lack of strategies to exploit them in diverse ways. Whilst i) methods for the photochemical perturbation of proteins and ii) photophysical protein probes and sensors are both known powerful tools, simultaneous methods for site- and context-specific photochemical modification of a protein side chain with concomitant modulation of photophysical properties would allow interrogation of protein function via diverse modes (potentially reporting simultaneously on structure and dynamics of ground- and reactive-state properties). Due to their mechanistic complexity, rational approaches for the design of suitable photochemical strategies can be difficult and non-intuitive. Here, we describe a high-throughput experimentation (HTE) strategy designed to allow the photochemical modification of a genetically-encoded, minimally disruptive ( zero-size), photophysically-active - yet typically unreactive and biologically-inert - unnatural amino acid (uAA) residue in proteins. The discovery of a novel dearomative, formal [4+3] photocycloaddition of imidazopyrimidine reagents which proceeds via photochemically generated C* intermediates with polyaromatic substrates enabled chemoselective application to the normally unreactive Trp-mimetic residue, 2-naphthylalanine (Npa). Npas site-selective installation allows dual photochemical and photophysical dearomative perturbation benignly and efficiently in proteins. Replacement of Trp in the archetypal apoptotic biosensor protein Annexin A5 (AnxV) enabled dual photochemical-photophysical determination of switched, conformationally-determined reactive states induced by Ca2+-binding, without any apparent functional perturbation of its in vitro or cellular recognition of phospholipids, indicating an ordered annexin mechanism. This ready and benign unification of photochemistry and photophysics suggests a general approach for using high-throughput light-mediated experimentation in artefact-free chemical biology to capture different functional states of proteins and to interrogate those states using combined photochemical-photophysical methods. HighlightsO_LIDevelopment of a general, high-throughput experimentation (HTE) approach enabled identification of an unprecedented photochemical reaction with potential for editing amino acid side chains within proteins. C_LIO_LIGenetic incorporation of 2-naphthylalanine, a minimally-disruptive ( zero-size) Trp mimic, enabled photochemical side chain editing with concomitant modulation of its distinctive photophysical properties in proteins. C_LIO_LIA naphthalene-tagged variant of the apoptotic biomarker protein AnxV enabled dual photochemical-photophysical exploration of its dynamic conformational states induced by Ca2+-binding whilst fully maintaining its functional capacity for in vitro or cellular recognition of phospholipids. C_LI

biochemistry↗

bioRxiv2025

Epididymal extracellular vesicles harbor and convey mRNA to sperm for transfer to zygotes

The epididymis plays a critical role in sperm maturation, including remodeling the sperm RNA payload. While small RNAs have been extensively studied in this context, the epididymal contribution to larger sperm RNAs, such as mRNAs, remains underexplored. mRNAs were among the first RNA species identified in sperm, yet their functional relevance has remained elusive, largely due to the translational quiescence of mature spermatozoa and the hypothesis that these RNAs are residual by-products of spermatogenesis. Yet, mRNAs carried by sperm have been detected in the zygote, indicating they could play a role beyond fertilization. However, if the soma, the epididymis, actively contributes mRNAs to sperm as it does small RNAs, has not been experimentally assessed. To investigate this, here, we provide a comprehensive analysis of the mRNA landscape of mouse sperm, epithelial cells and extracellular vesicles (EVs) isolated from the proximal (caput) and distal (cauda) epididymis. Through this analysis and sperm-EV co-incubation experiments we demonstrate the transfer of mRNAs from epididymal EVs to sperm. Further, through sperm RNA microinjection into zygotes we uncover gene regulation in the early embryo driven by the introduction of sperm RNAs, specific to large RNA species. These findings ultimately reveal the dynamic mRNA profile of sperm that is delivered to the egg and demonstrate that RNA species beyond small RNAs are capable of influencing preimplantation embryo gene expression.

cell biology↗

bioRxiv2024

A high-resolution model of gene expression during Gossypium hirsutum (cotton) fiber development

Cotton fiber development relies on complex and intricate biological processes to transform newly differentiated fiber initials into the mature, extravagantly elongated cellulosic cells that are the foundation of this economically important cash crop. Here we extend previous research into cotton fiber development by employing controlled conditions to minimize variability and utilizing time-series sampling and analyses to capture daily transcriptomic changes from early elongation through the early stages of secondary wall synthesis (6 to 24 days post anthesis; DPA). A majority of genes are expressed in fiber, largely partitioned into two major coexpression modules that represent genes whose expression generally increases or decreases during development. Differential gene expression reveals a massive transcriptomic shift between 16 and 17 DPA, corresponding to the onset of the transition phase that leads to secondary wall synthesis. Subtle gene expression changes are captured by the daily sampling, which are discussed in the context of fiber development. Coexpression and gene regulatory networks are constructed and associated with phenotypic aspects of fiber development, including turgor and cellulose production. Key genes are considered in the broader context of plant secondary wall synthesis, noting their known and putative roles in cotton fiber development. The analyses presented here highlight the importance of fine-scale temporal sampling on understanding developmental processes and offer insight into genes and regulatory networks that may be important in conferring the unique fiber phenotype.

cell biology↗

bioRxiv2024

Daily glycome and transcriptome profiling reveals polysaccharide structures and glycosyltransferases critical for cotton fiber growth

Cotton fiber length and strength are key determinants of its quality. Dynamic changes in the pectin, xyloglucan, xylan, and cellulose polysaccharide epitopes content during fiber growth contribute to complex remodeling of fiber cell wall (CW) and quality. Detailed knowledge about polysaccharide compositional and structural alteration in the fiber during fiber elongation and strengthening is vastly limited. Here, large-scale glycome profiling coupled with fiber phenotype and transcriptome profiling was conducted on fiber collected daily covering the most critical fiber developmental window. High temporal resolution profiling allowed us to identify specific polysaccharide epitopes associated with distinct fiber phenotypes that might contribute to fiber quality. This study revealed the critical role of highly branched RG-I pectin epitopes such as, {beta}-1,4-linked-galactans, {beta}-1,6-linked-galactans, and arabinogalactans, in addition to earlier reported homogalacturonans and xyloglucans in the formation of cotton-fiber-middle-lamella and contributing to fiber plasticity and elongation. We also propose the essential role of heteroxylans (Xyl-MeGlcA and Xyl-3Ar), as a guiding factor for secondary CW cellulose-microfibril arrangement, thus contributing to fiber strength. Correlation analysis of glycome and transcriptome data identified several key putative glycosyltransferases involved in synthesizing the critical polysaccharide epitopes. Novel details discovered here provide a foundation to identify molecular factors that dictate important fiber traits.

plant biology↗

bioRxiv2022

The Gossypium herbaceum L. Wagad genome as a resource for understanding cotton domestication

Gossypium herbaceum is a species of cotton native to Africa and Asia that is one of the two domesticated diploids. Together with its sister-species G. arboreum, these A-genome taxa represent models of the extinct A-genome donor of modern polyploid cotton, which provide about 95% of cotton grown worldwide. As part of a larger effort to characterize variation and improve resources among diverse diploid and polyploid cotton genomes, we sequenced and assembled the genome of G. herbaceum cultivar (cv) Wagad, representing the first domesticated accession for this species. This chromosome-level genome was generated using a combination of PacBio long-read technology, HiC, and Bionano optical mapping and compared to existing genome sequences in cotton. We compare the genome of this cultivar to the existing genome of wild G. herbaceum subspecies africanum to elucidate changes in the G. herbaceum genome concomitant with domestication, and extend these analyses to gene expression using available RNA-seq. Our results demonstrate the utility of the G. herbaceum cv Wagad genome in understanding domestication in the diploid species, which could inform modern breeding programs.

genomics↗