Biology subjects

Schilmiller, A. L.

Publications and source records attributed to Schilmiller, A. L..

6 recordsLinked to original sources

bioRxiv2025

Dynamic changes to the plastoglobule lipidome and proteome in heat-stressed maize

Heat stress is a major environmental factor affecting the physiology and productivity of agricultural crops including maize (Zea mays). Plastoglobules, lipid-protein structures in chloroplasts, play a key role in stress resilience by modulating lipid metabolism and maintaining chloroplast function. However, the molecular functions of plastoglobules and their compositions are enigmatic. Our study investigated the molecular changes in the protein and lipid compositions of plastoglobules and thylakoids at six time points over the course of an imposed heat stress and recovery treatment in B73 inbred maize. Results indicate a progressive increase in plastoglobule size and number, and proliferation of adjacent cytosolic lipid droplets, correlating with the duration of heat exposure. Significant alterations in lipid composition, particularly in levels of triacylglycerol, plastoquinone derivatives (PQ-C, B & E) and the fatty acid phytol ester, 12:0-phytol, suggest a protective role in membrane remodeling and oxidative defense. Furthermore, heat-induced upregulation of key plastoglobule-associated proteins, such as Fibrillin 1a & 2, Fructose-bisphosphate Aldolase 2, 13-Lipoxygenase 10/11, and Allene Oxide Synthase 2b were observed, indicating their involvement in stress mitigation. These findings provide novel insights into the adaptive mechanisms of plastoglobules under heat stress in the context of remodeling at the thylakoid and highlight potential targets for improving maize resilience and leveraging the plastoglobules for crop improvement. Understanding these responses could contribute to developing heat-resilient maize cultivars in the face of global climate change.

plant biology↗

bioRxiv2025

Dynamic changes to the plastoglobule lipidome and proteome in water-deficient maize

AbstractDrought represents one of the most severe challenges faced by agriculture and leveraging resources to promote crop resilience is critical. The plastoglobule lipid droplets of chloroplasts, present in all photosynthetic organisms, are suggested to be a major orchestrator of adaptive responses to environmental perturbations, thus representing a potentially significant, untapped target for enhancement of crop resilience. Yet, the functions of plastoglobules are unclear and their molecular composition incompletely described. Here, we provide a thorough investigation of the protein and lipid compositions of plastoglobules and thylakoids at six time-points over the course of a water-deficit and recovery treatment in B73 inbred maize. Our results establish the prominent components of the plastoglobule polar lipid surface and neutral lipid interior in an important crop species, including the presence of mono- and di-galactosyl diacylglycerol lipids enriched in saturated acyl groups, and the prevalence of various triacylglycerols and plastoquinone-9 derivatives. Quantitative proteomics identifies prominent Fibrillins and Activity of bc1 Complex Kinases at the plastoglobule as well as many proteins with known or putative roles in prenyl-lipid and redox metabolism. A remarkably high proportion of the Fibrillin 4 on the plastoglobules coincided with a preponderance of plastoquinone-9, supporting a role for Fibrillin 4 in plastoquinone accumulation at plastoglobules. Collectively, our results provide a solid foundation for the study of plastoglobules in crop plants.

plant biology↗

bioRxiv2022

Stereochemistry Determines Immune Cellular Responses to Polylactide Implants

Repeating L- and D-chiral configurations determine polylactide (PLA) stereochemistry which affects its thermal and physicochemical properties, including degradation profiles. Clinically, degradation of implanted PLA biomaterials promotes prolonged inflammation and excessive fibrosis, but the role of PLA stereochemistry is unclear. Additionally, although PLA of varied stereochemistries cause differential immune responses in-vivo, this observation has yet to be effectively modeled in-vitro. A bioenergetic model was applied to study immune cellular responses to PLA containing > 99% L-lactide (PLLA), > 99% D-lactide (PDLA) and a 50/50 melt-blend of PLLA and PDLA (stereocomplex PLA). Stereocomplex PLA breakdown products increased IL-1{beta}, TNF- and IL-6 protein levels but not MCP-1. Expression of these proinflammatory cytokines is mechanistically driven by increases in glycolysis in primary macrophages. In contrast, PLLA and PDLA degradation products selectively increase MCP-1 protein expression. Whereas both oxidative phosphorylation and glycolysis are increased with PDLA, only oxidative phosphorylation is increased with PLLA. For each biomaterial, glycolytic inhibition reduces proinflammatory cytokines and markedly increases anti-inflammatory (IL-10) protein levels; differential metabolic changes in fibroblasts were observed. These findings provide mechanistic explanations for the diverse immune responses to PLA of different stereochemistries, and underscore the pivotal role of immunometabolism on the biocompatibility of biomaterials applied in medicine.

bioengineering↗

bioRxiv2021

Lipid Bilayer Induces Contraction of the Denatured State Ensemble of a Helical-Bundle Membrane Protein

Defining the denatured state ensemble (DSE) and intrinsically disordered proteins is essential to understanding protein folding, chaperone action, degradation, translocation and cell signaling. While a majority of studies have focused on water-soluble proteins, the DSE of membrane proteins is much less characterized. Here, we reconstituted the DSE of a helical-bundle membrane protein GlpG of Escherichia coli in native lipid bilayers and measured the DSEs conformation and compactness. The DSE was obtained using steric trapping, which couples spontaneous denaturation of a doubly biotinylated GlpG to binding of two bulky monovalent streptavidin molecules. Using limited proteolysis and mass spectrometry, we mapped the flexible regions in the DSE. Using our paramagnetic biotin derivative and double electron-electron resonance spectroscopy, we determined the dimensions of the DSE. Finally, we employed our Upside model for molecular dynamics simulations to generate the DSE including the collapsed and fully expanded states in a bilayer. We find that the DSE is highly dynamic involving the topology changes of transmembrane segments and their unfolding. The DSE is expanded relative to the native state, but only to 55-90% of the fully expanded condition. The degree of expansion depends on the chemical potential with regards to local packing and the lipid composition. Our result suggests that the E. colis native lipid bilayer promotes the association of helices in the DSE of membrane proteins and, probably in general, facilitating interhelical interactions. This tendency may be the outcome of a general lipophobic effect of proteins within the cell membranes. SignificanceHere, we delineate the conformation of the denatured state ensemble (DSE) of a membrane protein confined in a native lipid bilayer and assay whether the bilayer permits full expansion or nonspecific collapse of the DSE. Using the intramembrane protease GlpG as a model, we find that the denatured state is a dynamic ensemble involving topological changes and local unfolding of transmembrane segments. The bilayer tends to contract the DSE relative to the fully lipid-solvated, expanded conformations while the degree of compactness is determined by the balance between protein-lipid, lipid-lipid and protein-protein interactions. These findings provide new insights into the lipid bilayer as a solvent that mediates folding, chaperone action, turnover and protein-protein interactions in cell membranes.

biophysics↗

bioRxiv2020

Domestication has altered within-plant trait variability in a crop plant

O_LIFor 10,000 years humans have altered plant traits through domestication and ongoing crop improvement, shaping plant form and function in agroecosystems. To date, studies have focused on how these processes have shaped whole-plant or average traits; however, plants also have characteristic levels of trait variability among their repeated parts, which can be heritable and mediate critical ecological interactions. As concerns about sustainable pest management increase, there is growing interest in approaches that increase trait diversity in crop agroecosystems. Here, we examine an under-appreciated scale of trait variation - among leaves, within plants - that may have changed through the process of domestication and improvement in a key crop. C_LIO_LIWe explore how levels of within-plant, among-leaf trait variability differ between cultivars and wild relatives of alfalfa (Medicago sativa), a key forage crop with an 8,000 year cultivation history. We grew individual plants from 30 wild populations and 30 cultivars, encompassing a range of domestication and improvement histories. For each plant, we quantify variability in a broad suite of physical, nutritive, and chemical leaf traits, including measures of chemical dissimilarity (beta diversity) among leaves. C_LIO_LIWe find that intra-individual trait variability has changed over the course of domestication and crop improvement, with effects often larger than changes in trait means. Cultivated alfalfa had elevated variability in SLA, trichomes, and C:N; increased diversity in defensive compounds; and reduced variability in phytochemical composition. We also elucidate fundamental associations between trait means and overall investment in secondary metabolites with patterns of among-leaf variability and chemical diversity. C_LIO_LIWe conclude that within-plant variability is an overlooked dimension of trait diversity in this globally critical agricultural crop. We find that trait variability is actually higher in cultivated plants compared to wild progenitors for multiple nutritive, physical, and chemical traits, highlighting a scale of variation that may mitigate loss of trait diversity at other scales in alfalfa agroecosystems and in other crops with similar domestication and improvement histories. C_LI

evolutionary biology↗

bioRxiv2018

Evolution of metabolic novelty: a trichome-expressed invertase creates specialized metabolic diversity in wild tomato

Plants produce myriad taxonomically restricted specialized metabolites. This diversity - and our ability to correlate genotype with phenotype - makes the evolution of these ecologically and medicinally important compounds interesting and experimentally tractable. Trichomes of tomato and other nightshade family plants produce structurally diverse protective compounds termed acylsugars. While cultivated tomato (Solanum lycopersicum) accumulates strictly acylsucroses, the South American wild relative Solanum pennellii produces copious amounts of acylglucoses. Genetic, transgenic and biochemical dissection of the S. pennellii acylglucose biosynthetic pathway identified a trichome gland cell expressed invertase-like enzyme that hydrolyzes acylsucroses (Sopen03g040490). This enzyme acts on the pyranose ring-acylated acylsucroses found in the wild tomato but not the furanose ring-decorated acylsucroses of cultivated tomato. These results show that modification of the core acylsucrose biosynthetic pathway leading to loss of furanose ring acylation set the stage for co-option of a general metabolic enzyme to produce a new class of protective compounds.

plant biology↗