Biology subjects

Lundquist, P. K.

Publications and source records attributed to Lundquist, P. K..

4 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↗

bioRxiv2023

An amphipathic helix drives interaction of Fibrillins with plastoglobule lipid droplets

Plastoglobule lipid droplets of chloroplasts serve complex roles affecting plant development, stress tolerance and photosynthesis. They harbor a set of approximately 42 proteins that collectively dictate plastoglobule functions. Due to the monolayer structure of plastoglobules which encompass a neutral lipid core, these proteins must associate monotopically on the plastoglobule surface. However, targeting determinants have not been identified for plastoglobule proteins, and the protein-membrane interaction mechanisms that establish the plastoglobule proteome remain unclear. Here, we demonstrate that plastoglobule-localized Fibrillins harbor an amphipathic helix at the lip of their {beta}-barrel that is necessary for proper plastoglobule association. Molecular dynamics simulations support the specific interaction of the amphipathic helix of AtFBN1a with membranes rich in lipid packing defects which are expected to be especially prevalent on the tightly curved surface of plastoglobules. Introduction of one of the amphipathic helices into stromal-or thylakoid-localized FBNs was ineffective at redirecting the proteins to plastoglobules, likely due to endogenous protein-protein interactions that override the influence of the amphipathic helix. Proteomic analyses indicate AtFBN1a influences the plastoglobule proteome through outcompeting and recruiting specific proteins. We also demonstrate that the plastoglobule-localized FBNs, AtFBN1a and AtFBN7a, bind unsaturated fatty acids, particularly C18:1, and that elimination of the amphipathic helix suppresses fatty acid binding in AtFBN1a, but promotes fatty acid binding in AtFBN7a. Predicted amphipathic helices can be identified on two-thirds of plastoglobule proteins, indicating the use of amphipathic helices may be a general mechanism by which proteins selectively associate with plastoglobules.

cell biology↗

bioRxiv2021

The plastoglobule-localized AtABC1K6 is a Mn2+-dependent protein kinase necessary for timely transition to reproductive growth

The Absence of bc1 Complex (ABC1) is an ancient, atypical protein kinase family that emerged prior to the archaeal-eubacterial divergence. Loss-of-function mutants in ABC1 genes are linked to respiratory defects in microbes and humans, and to compromised photosynthetic performance and stress tolerance in plants. However, demonstration of protein kinase activity remains elusive, hampering their study. Here, we investigate a homolog from Arabidopsis thaliana, AtABC1K6, and demonstrate in vitro protein kinase activity as autophosphorylation, which we replicate with a human ABC1 ortholog. We show that AtABC1K6 protein kinase activity requires an atypical buffer composition, including Mn2+ as divalent cation co-factor and a low salt concentration. AtABC1K6 associates with plastoglobule lipid droplets of A. thaliana chloroplasts, along with five paralogs. Protein kinase activity associated with isolated A. thaliana plastoglobules was inhibited at higher salt concentrations, but could accommodate Mg2+ as well as Mn2+, indicating salt sensitivity, but not the requirement for Mn2+, may be a general characteristic of ABC1s. Loss of functional AtABC1K6 impairs the developmental transition from vegetative to reproductive growth. This phenotype is complemented by the wild-type sequence of AtABC1K6 but not by a kinase-dead point mutant in the unique Ala-triad of the ATP-binding pocket, demonstrating the physiological relevance of the proteins kinase activity. We suggest that ABC1s are bona fide protein kinases with a unique regulatory mechanism. Our results open the door to detailed functional and mechanistic studies of ABC1s and plastoglobules. SIGNIFICANCE STATEMENTThe Absence of bc1 Complex (ABC1) is an ancient, atypical protein kinase family with enigmatic physiological roles in a wide range of species including plants, humans and microbes. While mutants demonstrate their critical role for organismal survival, their study has been severely hampered by the previous inability to determine catalytic function. Here, we demonstrate in vitro protein kinase activity with an A. thaliana homolog, AtABC1K6. Loss of functional AtABC1K6 impairs the developmental transition from vegetative to reproductive growth. The lack of phenotypic complementation with a kinase-dead point mutant demonstrates the physiological relevance of the proteins kinase activity. Our results present the experimental means to investigate the targets, functions, and regulation of ABC1s.

plant biology↗