A Core Metabolome Response of Maize Leaves Subjected to Long-Duration Abiotic Stresses

Abiotic stresses reduce crop growth and yield in part by disrupting metabolic homeostasis and triggering responses that change the metabolome. Experiments designed to understand the mechanisms underlying these metabolomic responses have usually not used agriculturally relevant stress regimes. We therefore subjected maize plants to drought, salt, or heat stresses that mimic field conditions and analyzed leaf responses at metabolome and transcriptome levels. Shared features of stress metabolomes included synthesis of raffinose, a compatible solute implicated in tolerance to dehydration. In addition, a marked accumulation of amino acids including proline, arginine, and γ-aminobutyrate combined with depletion of key glycolysis and tricarboxylic acid cycle intermediates indicated a shift in balance of carbon and nitrogen metabolism in stressed leaves. Involvement of the γ-aminobutyrate shunt in this process is consistent with its previously proposed role as a workaround for stress-induced thiamin-deficiency. Although convergent metabolome shifts were correlated with gene expression changes in affected pathways, patterns of differential gene regulation induced by the three stresses indicated distinct signaling mechanisms highlighting the plasticity of plant metabolic responses to abiotic stress.

Early Transcriptomic Response to Burn injury: Severe Burns are Associated with Immune Pathway Shutdown

Burn injury induces a systemic hyperinflammatory response with detrimental side effects. Studies have described the biochemical changes induced by severe burns, but the transcriptome response is not well characterized. The goal of this work is to characterize the blood transcriptome after burn injury. Burn patients presenting to a regional center between 2012-2017 were prospectively enrolled. Blood was collected on admission and at predetermined time points (hours 2, 4, 8, 12, 24). RNA was isolated and transcript levels were measured with a gene expression microarray. To identify differentially regulated genes (FDR≤0.1) by burn injury severity, patients were grouped by total body surface area (TBSA) above or below 20% and statistically enriched pathways were identified. Sixty-eight patients were analyzed, most patients were male with a median age of 41 (IQR, 30.5-58.5) years, and TBSA of 20% (11-34%). Thirty-five patients had %TBSA injury ≥20%, and this group experienced greater mortality (26% vs. 3%, p=0.008). Comparative analysis of genes from patients with </≥20% TBSA revealed 1505, 613, 380, 63, 1357, and 954 differentially expressed genes at hours 0, 2, 4, 8, 12 and 24 respectively. Pathway analysis revealed an initial upregulation in several immune/inflammatory pathways within the ≥20% TBSA groups followed by shutdown. Severe burn injury is associated with an early proinflammatory immune response followed by shutdown of these pathways. Examination of the immunoinflammatory response to burn injury through differential gene regulation and associated immune pathways by injury severity may identify mechanistic targets for future intervention.

Millipede genomes reveal unique adaptation of genes and microRNAs during myriapod evolution

The Myriapoda including millipedes and centipedes is of major importance in terrestrial ecology and nutrient recycling. Here, we sequenced and assembled two chromosomal-scale genomes of millipedes Helicorthomorpha holstii (182 Mb, N50 18.11 Mb mainly on 8 pseudomolecules) and Trigoniulus corallinus (449 Mb, N50 26.78 Mb mainly on 15 pseudomolecules). Unique defense systems, genomic features, and patterns of gene regulation in millipedes, not observed in other arthropods, are revealed. Millipedes possesses a unique ozadene defensive gland unlike the venomous forcipules in centipedes. Sets of genes associated with anti-microbial activity are identified with proteomics, suggesting that the ozadene gland is not primarily an antipredator adaptation (at least in T. corallinus). Macro-synteny analyses revealed highly conserved genomic blocks between centipede and the two millipedes. Tight Hox and the first loose ecdysozoan ParaHox homeobox clusters are identified, and a myriapod-specific genomic rearrangement including Hox3 is also observed. The Argonaute proteins for loading small RNAs are duplicated in both millipedes, but unlike insects, an argonaute duplicate has become a pseudogene. Evidence of post-transcriptional modification in small RNAs, including species-specific microRNA arm switching that provide differential gene regulation is also obtained. Millipede genomes reveal a series of unique genomic adaptations and microRNA regulation mechanisms have occurred in this major lineage of arthropod diversity. Collectively, the two millipede genomes shed new light on this fascinating but poorly understood branch of life, with a highly unusual body plan and novel adaptations to their environment.

Joint inference and alignment of genome structures enables characterization of compartment-independent reorganization across cell types

Cell-type-specific chromosome conformation is correlated with differential gene regulation. Broad compartmentalization into two compartments (A & B) is proposed to be the main driver of cell-specific chromosome organization. However it is unclear what fraction of chromosome conformation changes between cell types and conditions is independent of changes in compartmentalization and whether any such compartment-independent reorganization is functionally important. We developed MultiMDS to jointly infer and align 3D chromosomal structures, thereby enabling a quantitative comparison of locus-specific changes across Hi-C datasets. We compared Hi-C datasets from yeast, which lack compartmentalization, grown with and without galactose. These comparisons confirmed known relocalizations as well as identifying additional examples. We also compared mammalian datasets across a variety of cell lines. We found a consistent enrichment for changes along the A/B compartment (nuclear interior/nuclear periphery) axis, even when comparing the same cell type from different individuals. Despite the prevalence of compartment changes, we consistently find compartment-independent relocalizations of loci that are within the A compartment in both compared cell types. Some such intra-compartment relocalizations involve loci that display enhancer-associated histone marks in one cell type and polycomb-associated histone marks in the other. MultiMDS thus enables a new way to compare chromosome conformations across two Hi-C datasets.Availabilityhttps://github.com/seqcode/multimds