Large-scale across species transcriptomic analysis identifies genetic selection signatures associated with longevity in mammals.

Lifespan varies significantly among mammals, with more than 100-fold difference between the shortest and longest living species. This natural difference may uncover the evolutionary forces and molecular features that define longevity. To understand the relationship between gene expression variation and longevity, we conducted a comparative transcriptomics analysis of liver, kidney, and brain tissues of 103 mammalian species. We found that few genes exhibit common expression patterns with longevity in the three organs analyzed. However, pathways related to translation fidelity, such as nonsense-mediated decay and eukaryotic translation elongation, correlated with longevity across mammals. Analyses of selection pressure found that selection intensity related to the direction of longevity-correlated genes is inconsistent across organs. Furthermore, expression of methionine restriction-related genes correlated with longevity and was under strong selection in long-lived mammals, suggesting that a common strategy is utilized by natural selection and artificial intervention to control lifespan. Our results indicate that lifespan regulation via gene expression is driven through polygenic and indirect natural selection.

A cytological revisit on parthenogenetic Artemia and the deficiency of a meiosis-specific recombinase DMC1 in the possible transition from bisexuality to parthenogenesis.

Although parthenogenesis is widespread in nature and known to have close relationships with bisexuality, the transitional mechanism is poorly understood. Artemia is an ideal model to address this issue because bisexuality and "contagious" obligate parthenogenesis independently exist in its congeneric members. In the present study, we first performed chromosome spreading and immunofluorescence to compare meiotic processes of Artemia adopting two distinct reproductive ways. The results showed that, unlike conventional meiosis in bisexual Artemia, meiosis II in parthenogenic Artemia is entirely absent and anaphase I is followed by a single mitosis-like equational division. Interspecific comparative transcriptomics showed that two central molecules in homologous recombination (HR), Dmc1 and Rad51, exhibited significantly higher expression in bisexual versus parthenogenetic Artemia. qRT-PCR indicated that the expression of both genes peaked at the early oogenesis and gradually decreased afterward. Knocking-down by RNAi of Dmc1 in unfertilized females of bisexual Artemia resulted in a severe deficiency of homologous chromosome pairing and produced univalents at the middle oogenesis stage, which was similar to that of parthenogenic Artemia, while in contrast, silencing Rad51 led to no significant chromosome morphological change. Our results indicated that Dmc1 is vital for HR in bisexual Artemia, and the deficiency of Dmc1 may be correlated with or even possibly one of core factors in the transition from bisexuality to parthenogenesis.

A Phylogenetic Framework to Simulate Synthetic Interspecies RNA-Seq Data.

Interspecies RNA-Seq datasets are increasingly common, and have the potential to answer new questions about the evolution of gene expression. Single-species differential expression analysis is now a well-studied problem that benefits from sound statistical methods. Extensive reviews on biological or synthetic datasets have provided the community with a clear picture on the relative performances of the available methods in various settings. However, synthetic dataset simulation tools are still missing in the interspecies gene expression context. In this work, we develop and implement a new simulation framework. This tool builds on both the RNA-Seq and the phylogenetic comparative methods literatures to generate realistic count datasets, while taking into account the phylogenetic relationships between the samples. We illustrate the usefulness of this new framework through a targeted simulation study, that reproduces the features of a recently published dataset, containing gene expression data in adult eye tissue across blind and sighted freshwater crayfish species. Using our simulated datasets, we perform a fair comparison of several approaches used for differential expression analysis. This benchmark reveals some of the strengths and weaknesses of both the classical and phylogenetic approaches for interspecies differential expression analysis, and allows for a reanalysis of the crayfish dataset. The tool has been integrated in the R package compcodeR, freely available on Bioconductor.

Comparative analyses suggest a link between mRNA splicing, stability, and RNA covalent modifications in flowering plants.

BACKGROUND: In recent years, covalent modifications on RNA nucleotides have emerged as pivotal moieties influencing the structure, function, and regulatory processes of RNA Polymerase II transcripts such as mRNAs and lncRNAs. However, our understanding of their biological roles and whether these roles are conserved across eukaryotes remains limited. RESULTS: In this study, we leveraged standard polyadenylation-enriched RNA-sequencing data to identify and characterize RNA modifications that introduce base-pairing errors into cDNA reads. Our investigation incorporated data from three Poaceae (Zea mays, Sorghum bicolor, and Setaria italica), as well as publicly available data from a range of stress and genetic contexts in Sorghum and Arabidopsis thaliana. We uncovered a strong enrichment of RNA covalent modifications (RCMs) deposited on a conserved core set of nuclear mRNAs involved in photosynthesis and translation across these species. However, the cohort of modified transcripts changed based on environmental context and developmental program, a pattern that was also conserved across flowering plants. We determined that RCMs can partly explain accession-level differences in drought tolerance in Sorghum, with stress-associated genes receiving a higher level of RCMs in a drought tolerant accession. To address function, we determined that RCMs are significantly enriched near exon junctions within coding regions, suggesting an association with splicing. Intriguingly, we found that these base-pair disrupting RCMs are associated with stable mRNAs, are highly correlated with protein abundance, and thus likely associated with facilitating translation. CONCLUSIONS: Our data point to a conserved role for RCMs in mRNA stability and translation across the flowering plant lineage.

Trichomes and unique gene expression confer insect herbivory resistance in Vitis labrusca grapevines.

BACKGROUND: Grapevine (Vitis) is one of the world's most valuable fruit crops, but insect herbivory can decrease yields. Understanding insect herbivory resistance is critical to mitigating these losses. Vitis labrusca, a wild North American grapevine species, has been leveraged in breeding programs to generate hybrid grapevines with enhanced abiotic and biotic stress resistance, rendering it a valuable genetic resource for sustainable viticulture. This study assessed the resistance of V. labrusca acc. 'GREM4' and Vitis vinifera cv. 'PN40024' grapevines to Popillia japonica (Japanese beetle) herbivory and identified morphological and genetic adaptations underlying this putative resistance. RESULTS: 'GREM4' displayed greater resistance to beetle herbivory compared to 'PN40024' in both choice and no-choice herbivory assays spanning periods of 30 min to 19 h. 'GREM4' had significantly higher average leaf trichome densities than 'PN40024' and beetles preferred to feed on the side of leaves with fewer trichomes. When leaves from each species that specifically did not differ in trichome densities were fed on by beetles, significantly less leaf area was damaged in 'GREM4' (3.29mm2) compared to 'PN40024' (9.80mm2), suggesting additional factors beyond trichomes contributed to insect herbivory resistance in 'GREM4'. Comparative transcriptomic analyses revealed 'GREM4' exhibited greater constitutive (0 h) expression of defense response and secondary metabolite biosynthesis genes compared to 'PN40024', indicative of heightened constitutive defenses. Upon herbivory, 'GREM4' displayed a greater number of differentially expressed genes (690) compared to 'PN40024' (502), suggesting a broader response. Genes up-regulated in 'GREM4' were enriched in terpene biosynthesis, flavonoid biosynthesis, phytohormone signaling, and disease defense-related functions, likely contributing to heighted insect herbivory defense, while genes differentially expressed in 'PN40024' under herbivory were enriched in xyloglucan, cell wall formation, and calcium ion binding. The majority of genes implicated in insect herbivory defense were orthologs with specific expression patterns in 'GREM4' and 'PN40024', but some paralogous and genome-specific genes also likely contributed to conferring resistance. CONCLUSIONS: Our findings suggest that 'GREM4' insect herbivory resistance was attributed to a combination of factors, including trichomes and unique constitutive and inducible expression of genes implicated in terpene, flavonoid, and phenylpropanoid biosynthesis, as well as pathogen defense.

Network analyses predict major regulators of resistance to early blight disease complex in tomato.

BACKGROUND: Early blight and brown leaf spot are often cited as the most problematic pathogens of tomato in many agricultural regions. Their causal agents are Alternaria spp., a genus of Ascomycota containing numerous necrotrophic pathogens. Breeding programs have yielded quantitatively resistant commercial cultivars, but fungicide application remains necessary to mitigate the yield losses. A major hindrance to resistance breeding is the complexity of the genetic determinants of resistance and susceptibility. In the absence of sufficiently resistant germplasm, we sequenced the transcriptomes of Heinz 1706 tomatoes treated with strongly virulent and weakly virulent isolates of Alternaria spp. 3 h post infection. We expanded existing functional gene annotations in tomato and using network statistics, we analyzed the transcriptional modules associated with defense and susceptibility. RESULTS: The induced responses are very distinct. The weakly virulent isolate induced a defense response of calcium-signaling, hormone responses, and transcription factors. These defense-associated processes were found in a single transcriptional module alongside secondary metabolite biosynthesis genes, and other defense responses. Co-expression and gene regulatory networks independently predicted several D clade ethylene response factors to be early regulators of the defense transcriptional module, as well as other transcription factors both known and novel in pathogen defense, including several JA-associated genes. In contrast, the strongly virulent isolate elicited a much weaker response, and a separate transcriptional module bereft of hormone signaling. CONCLUSIONS: Our findings have predicted major defense regulators and several targets for downstream functional analyses. Combined with our improved gene functional annotation, they suggest that defense is achieved through induction of Alternaria-specific immune pathways, and susceptibility is mediated by modulating hormone responses. The implication of multiple specific clade D ethylene response factors and upregulation of JA-associated genes suggests that host defense in this pathosystem involves ethylene response factors to modulate jasmonic acid signaling.

Comparative transcriptomics suggests a potential realizator gene for carapace expansion in longtail tadpole shrimp, Triops longicaudatus (Branchiopoda: Notostraca).

The origin of morphological innovation has been extensively studied within evolutionary developmental biology (evo-devo). Recent studies have demonstrated that the developmental module for double-layered epithelial outgrowths is conserved between the insect wings and branchiopod crustacean carapace, thereby introducing homology among these diverse structures. However, evo-devo studies on the branchiopod crustacean carapace have been primarily limited to a single species, the water flea Daphnia magna, leaving the gene regulatory network governing carapace development not comprehensively understood. Furthermore, realizator genes downstream of the character identity mechanism (ChIM) for bilayered epithelial development remain inadequately described. In this study, we analyzed tissue-specific transcriptional profiles in the developing longtail tadpole shrimp, Triops longicaudatus. We observed significant upregulation of papilin in the carapace-bearing head, along with its expression in both the carapace and the trunk limb lobes. Based on these results, we hypothesize that differential expression of papilin is involved in the disproportional growth of Triops carapace. Our findings will contribute to elucidating the diversification of double-layered epithelial outgrowths across distant arthropod lineages.

Syntrichia ruralis: emerging model moss genome reveals a conserved and previously unknown regulator of desiccation in flowering plants.

Water scarcity, resulting from climate change, poses a significant threat to ecosystems. Syntrichia ruralis, a dryland desiccation-tolerant moss, provides valuable insights into survival of water-limited conditions. We sequenced the genome of S. ruralis, conducted transcriptomic analyses, and performed comparative genomic and transcriptomic analyses with existing genomes and transcriptomes, including with the close relative S. caninervis. We took a genetic approach to characterize the role of an S. ruralis transcription factor, identified in transcriptomic analyses, in Arabidopsis thaliana. The genome was assembled into 12 chromosomes encompassing 21 169 protein-coding genes. Comparative analysis revealed copy number and transcript abundance differences in known desiccation-associated gene families, and highlighted genome-level variation among species that may reflect adaptation to different habitats. A significant number of abscisic acid (ABA)-responsive genes were found to be negatively regulated by a MYB transcription factor (MYB55) that was upstream of the S. ruralis ortholog of ABA-insensitive 3 (ABI3). We determined that this conserved MYB transcription factor, uncharacterized in Arabidopsis, acts as a negative regulator of an ABA-dependent stress response in Arabidopsis. The new genomic resources from this emerging model moss offer novel insights into how plants regulate their responses to water deprivation.

Expression-environment associations in transcriptomic heat stress responses for a global plant lineage.

The increasing frequency and severity of heatwaves will intensify stress on plants. Given regional variation in heatwave exposure and expected differences in thermal tolerance between species it is unlikely that all plant species will be affected equally by climate change. However, little is currently known about variation in the responses of plants to heat stress, or how those responses differ among closely related species adapted to different environments. Here we quantify the response of 17 Acacia species (175 RNA-seq libraries), from across Australia's diverse biomes, to a multi-day experimental heatwave treatment to identify variation in transcriptomic and physiological responses to heat stress. Genes with known heat response functions showed consistent responses across Acacia species. Up to 10% of all genes and over 100 gene families showed significant clinal variation in the magnitude of their expression plasticity across species. Specifically, gene families linked to the temperature stress response were overrepresented among significant relationships with home range temperature conditions. Gene expression responses seen on the first day of the heatwave were more frequently associated with home range climates, while expression responses by day four were more commonly related to photosystem II acclimation. Comparative transcriptomics on non-model species has the potential to provide key information on stress response plasticity, especially when linked with our understanding of model species. Our study indicates that the pressing challenge to identifying potentially vulnerable species to climate change could be benefited by the further exploration of clinal variation in transcriptome plasticity.

Integrating multiple statistical indices to measure the stability of photosynthetic pigment content and composition in Brassica juncea (L.) Czern germplasm under varying environmental conditions.

Understanding the stability of photosynthetic pigments is crucial for developing crop cultivars with high productivity and resilience to the environmental stresses. This study leveraged GGE biplot, WAASB, and MTSI indices to assess the stability of content and composition of photosynthetic pigments in leaves and siliques of 286 Brassica juncea (L.) Czern. genotypes across three environments. The GGE biplot analysis identified NRCQR-9901 as the best genotype in terms of chlorophyll 'a' under conditions of high irradiance and long days (E1). For chlorophyll 'b' and total chlorophyll, NC-533728 performed the best. AJ-2 and NPJ-208 had the maximum total carotenoids levels in leaves. RLC-2 was characterized by maximum values for chlorophyll a, chlorophyll b, and total chlorophyll in the siliques. The low irradiance, short days, and moderate to high temperatures (E2) seemed perfect for the synthesis of photosynthetic pigments. NPJ-182 shows the maximum concentrations of chlorophyll 'a', total chlorophyll, and total carotenoids in leaves. Conversely, IC-597869, RE-389, and IC-597894 exhibited the highest concentrations of chlorophyll 'b' under an environment characterized by low light intensity, shorter daylights, and low temperatures (E3) during flowering and siliqua formation stages. The combined analysis found NPJ-182, NC-533728, CN-105233, RLC-2, CN-101846, JA-96, PBR-357, JM-3, and DTM-34 as top performers with high stability. Comparative transcriptome analysis with two stable and high-performing genotypes (PBR-357 and DTM-34) and two average performers revealed upregulation of critical photosynthesis-related genes (ELIP1, CAB3.1, ELIP1.5, and LHCB5) in top performers. This study identified promising trait donors for use in breeding programs aimed at improving the mustard crop's photosynthetic efficiency, productivity, and stability.

Defective cytokinin signaling reprograms lipid and flavonoid gene-to-metabolite networks to mitigate high salinity in Arabidopsis.

Cytokinin (CK) in plants regulates both developmental processes and adaptation to environmental stresses. Arabidopsis histidine phosphotransfer ahp2,3,5 and type-B Arabidopsis response regulator arr1,10,12 triple mutants are almost completely defective in CK signaling, and the ahp2,3,5 mutant was reported to be salt tolerant. Here, we demonstrate that the arr1,10,12 mutant is also more tolerant to salt stress than wild-type (WT) plants. A comprehensive metabolite profiling coupled with transcriptome analysis of the ahp2,3,5 and arr1,10,12 mutants was conducted to elucidate the salt tolerance mechanisms mediated by CK signaling. Numerous primary (e.g., sugars, amino acids, and lipids) and secondary (e.g., flavonoids and sterols) metabolites accumulated in these mutants under nonsaline and saline conditions, suggesting that both prestress and poststress accumulations of stress-related metabolites contribute to improved salt tolerance in CK-signaling mutants. Specifically, the levels of sugars (e.g., trehalose and galactinol), amino acids (e.g., branched-chain amino acids and γ-aminobutyric acid), anthocyanins, sterols, and unsaturated triacylglycerols were higher in the mutant plants than in WT plants. Notably, the reprograming of flavonoid and lipid pools was highly coordinated and concomitant with the changes in transcriptional levels, indicating that these metabolic pathways are transcriptionally regulated by CK signaling. The discovery of the regulatory role of CK signaling on membrane lipid reprogramming provides a greater understanding of CK-mediated salt tolerance in plants. This knowledge will contribute to the development of salt-tolerant crops with the ability to withstand salinity as a key driver to ensure global food security in the era of climate crisis.

Genomic and transcriptomic analyses support a silk gland origin of spider venom glands.

BACKGROUND: Spiders comprise a hyperdiverse lineage of predators with venom systems, yet the origin of functionally novel spider venom glands remains unclear. Previous studies have hypothesized that spider venom glands originated from salivary glands or evolved from silk-producing glands present in early chelicerates. However, there is insufficient molecular evidence to indicate similarity among them. Here, we provide comparative analyses of genome and transcriptome data from various lineages of spiders and other arthropods to advance our understanding of spider venom gland evolution. RESULTS: We generated a chromosome-level genome assembly of a model spider species, the common house spider (Parasteatoda tepidariorum). Module preservation, GO semantic similarity, and differentially upregulated gene similarity analyses demonstrated a lower similarity in gene expressions between the venom glands and salivary glands compared to the silk glands, which questions the validity of the salivary gland origin hypothesis but unexpectedly prefers to support the ancestral silk gland origin hypothesis. The conserved core network in the venom and silk glands was mainly correlated with transcription regulation, protein modification, transport, and signal transduction pathways. At the genetic level, we found that many genes in the venom gland-specific transcription modules show positive selection and upregulated expressions, suggesting that genetic variation plays an important role in the evolution of venom glands. CONCLUSIONS: This research implies the unique origin and evolutionary path of spider venom glands and provides a basis for understanding the diverse molecular characteristics of venom systems.

Comparative Transcriptome Analysis of T. rubrum, T. mentagrophytes, and M. gypseum Dermatophyte Biofilms in Response to Photodynamic Therapy.

Dermatophyte biofilms frequently count for inadequate responses and resistance to standard antifungal treatments, resulting in refractory chronic onychomycosis infection. Although antimicrobial photodynamic therapy (aPDT) has clinically proven to exert significant antifungal effects or even capable of eradicating dermatophyte biofilms, considerably less is known about the molecular mechanisms underlying aPDT and the potential dysregulation of signaling networks that could antagonize its action. The aim of this study is to elucidate the molecular mechanisms underlining aPDT combat against dermatophyte biofilm in recalcitrant onychomycosis and to decipher the potential detoxification processes elicited by aPDT, facilitating the development of more effective photodynamic interventions. We applied genome-wide comparative transcriptome analysis to investigate how aPDT disrupting onychomycosis biofilm formed by three distinct dermatophytes, including Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum gypseum, the most frequently occurring pathogenic species. In total, 352.13 Gb of clean data were obtained for the transcriptomes of dermatophyte biofilms with or without aPDT treatment, resulting in 2,422.42 million reads with GC content of 51.84%, covering 99.9%, 98.5% and 99.4% of annotated genes of T. rubrum, T. mentagrophytes, and M. gypseum, respectively. The genome-wide orthologous analysis identified 6624 transcribed single-copy orthologous genes in all three species, and 36.5%, 6.8% and 17.9% of which were differentially expressed following aPDT treatment. Integrative orthology analysis demonstrated the upregulation of oxidoreductase activities is a highly conserved detoxification signaling alteration in response to aPDT across all investigated dermatophyte biofilms. This study provided new insights into the molecular mechanisms underneath anti-dermatophyte biofilm effects of aPDT and successfully identified a conserved detoxification regulation upon the aPDT application.

Integrated Morphological, Comparative Transcriptomic, and Metabolomic Analyses Reveal Mechanisms Underlying Seasonal Patterns of Variation in Spines of the Giant Spiny Frog (Quasipaa spinosa).

Quasipaa spinosa, commonly known as the spiny frog, is an economically valued amphibian in China prized for its tender meat and nutritional value. This species exhibits marked sexual dimorphism, most notably the prominent spiny structures on males that are pivotal for mating success and species identification. The spines of Q. spinosa exhibit strong seasonal variation, changing significantly with the reproductive cycle, which typically spans from April to October. Sexually mature males develop densely packed, irregularly arranged round papillae with black spines on their chests during the breeding season, which may then reduce or disappear afterward, while females have smooth chest skin. Despite their ecological importance, the developmental mechanisms and biological functions of these spines have been inadequately explored. This study integrates morphological, transcriptomic, and metabolomic analyses to elucidate the mechanisms underlying the seasonal variation in spine characteristics of Q. spinosa. Our results demonstrate that spine density inversely correlates with body size and that spine development is accompanied by significant changes in epidermal thickness and keratinization during the breeding season. Comparative transcriptomic analysis across different breeding stages revealed significant gene expression alterations in pathways related to extracellular matrix interactions, tyrosine metabolism, Wnt signaling, and melanogenesis. Metabolomic analysis further identified significant seasonal shifts in metabolites essential for energy metabolism and melanin synthesis, including notable increases in citric acid and ß-alanine. These molecular changes are consistent with the observed morphological adaptations, suggesting a complex regulatory mechanism supporting spine development and functionality. This study provides novel insights into the molecular basis of spine morphogenesis and its seasonal dynamics in Q. spinosa, contributing valuable information for the species' conservation and aquaculture.

Genetic diversity and gene expression diversity shape the adaptive pattern of the aquatic plant Batrachium bungei along an altitudinal gradient on the Qinghai-Tibet plateau.

It is an intriguing issue of evolutionary biology how genetic diversity and gene expression diversity shape the adaptive patterns. Comparative transcriptomic studies of wild populations in extreme environments provide critical insights into the relative contribution of genetic and expressive components. In this study, we analyzed the genetic diversity and gene expression diversity of 20 populations of the aquatic plant Batrachium bungei along elevations ranging from 2690 to 4896 m on the Qinghai-Tibet plateau (QTP). Based on single nucleotide polymorphisms (SNPs) and gene expression data from 100 individuals of B. bungei, we found that variation in genetic sequence was more sensitive to detect weak differentiation than gene expression. Using 292,613 high-quality SNPs, we documented a significant phylogeographical structure, a low within-population genetic diversity, and a high inter-population genetic differentiation in B. bungei populations. Analysis of relationship between geographic distance, genetic distance, and gene expression similarity showed that geographic isolation shaped gene flow patterns but not gene expression patterns. We observed a negative relationship between genetic diversity and gene expression diversity within and among B. bungei populations, and we demonstrated that as environmental conditions worsen with increasing altitude, genetic diversity played an increased role in maintaining the stability of populations, while the corresponding role of gene expression diversity decreased. These results suggested that genetic diversity and gene expression diversity might act as a complementary mechanism contributing to the long-term survival of B. bungei in extreme environments.

Comparative Transcriptome Analyses Provide New Insights into the Evolution of Divergent Thermal Resistance in Two Eel Gobies.

Adaptation to thermal conditions in tidal mudflats always involves tolerating frequent fluctuations and often extreme environmental temperatures. Regulation of gene expression plays a fundamental role in the evolution of these thermal adaptations. To identify the key gene regulatory networks associated with the thermal adaptation, we investigated the capability of cold tolerance, as well as the transcriptomic changes under cold stress in two mudflat inhabitants (Odontamblyopus lacepedii and O. rebecca) with contrasting latitude affinity. Our results revealed a remarkable divergent capacity of cold tolerance (CTmin: 0.61 °C vs. 9.57 °C) between the two gobies. Analysis of transcriptomic changes under cold stress unveiled 193 differentially expressed genes exhibiting similar expression profiles across all tissues and species, including several classic metabolic and circadian rhythm molecules such as ACOD and CIART that may represent the core cold response machinery in eel gobies. Meanwhile, some genes show a unique expression spectrum in the more cold-tolerant O. lacepedii suggesting their roles in the enhanced cold tolerance and hence the extreme thermal adaptations. In addition, a weighted gene co-expression network analysis (WGCNA) revealed a subset of metabolic hub genes including MYH11 and LIPT2 showing distinct down-regulation in O. lacepedii when exposed to cold stress which highlights the role of reduced energy consumption in the enhanced cold tolerance of eel gobies. These findings not only provide new insights into how mudflat teleosts could cope with cold stress and their potential evolutionary strategies for adapting to their thermal environment, but also have important implications for sound management and conservation of their fishery resources in a scenario of global climate warming in the marine realm.

A novel TF molecular switch-mechanism found in two contrasting ecotypes of a psammophyte, Agriophyllum squarrosum, in regulating transcriptional drought memory.

BACKGROUND: Prior drought stress may change plants response patterns and subsequently increase their tolerance to the same condition, which can be referred to as "drought memory" and proved essential for plants well-being. However, the mechanism of transcriptional drought memory in psammophytes remains unclear. Agriophyllum squarrosum, a pioneer species on mobile dunes, is widely spread in Northern China's vast desert areas with outstanding ability of water use efficiency. Here we conducted dehydration-rehydration treatment on A. squarrosum semi-arid land ecotype AEX and arid land ecotype WW to dissect the drought memory mechanism of A. squarrosum, and to determine the discrepancy in drought memory of two contrasting ecotypes that had long adapted to water heterogeneity. RESULT: Physiological traits monitoring unveiled the stronger ability and longer duration in drought memory of WW than that of AEX. A total of 1,642 and 1,339 drought memory genes (DMGs) were identified in ecotype AEX and WW, respectively. Furthermore, shared DMGs among A. squarrosum and the previously studied species depicted that drought memory commonalities in higher plants embraced pathways like primary and secondary metabolisms; while drought memory characteristics in A. squarrosum were mainly related to response to heat, high light intensity, hydrogen peroxide, and dehydration, which might be due to local adaptation to desert circumstances. Heat shock proteins (HSPs) occupied the center of the protein-protein interaction (PPI) network in drought memory transcription factors (TF), thus playing a key regulatory role in A. squarrosum drought memory. Co-expression analysis of drought memory TFs and DMGs uncovered a novel regulating module, whereby pairs of TFs might function as molecular switches in regulating DMG transforming between high and low expression levels, thus promoting drought memory reset. CONCLUSION: Based on the co-expression analysis, protein-protein interaction prediction, and drought memory metabolic network construction, a novel regulatory module of transcriptional drought memory in A. squarrosum was hypothesized here, whereby recurrent drought signal is activated by primary TF switches, then amplified by secondary amplifiers, and thus regulates downstream complicated metabolic networks. The present research provided valuable molecular resources on plants' stress-resistance basis and shed light on drought memory in A. squarrosum.

Resolving intergenotypic Striga resistance in sorghum.

Genetic underpinnings of host-pathogen interactions in the parasitic plant Striga hermonthica, a root parasitic plant that ravages cereals in sub-Saharan Africa, are unclear. We performed a comparative transcriptome study on five genotypes of sorghum exhibiting diverse resistance responses to S. hermonthica using weighted gene co-expression network analysis (WGCNA). We found that S. hermonthica elicits both basal and effector-triggered immunity-like a bona fide pathogen. The resistance response was genotype specific. Some resistance responses followed the salicylic acid-dependent signaling pathway for systemic acquired resistance characterized by cell wall reinforcements, lignification, and callose deposition, while in others the WRKY-dependent signaling pathway was activated, leading to a hypersensitive response. In some genotypes, both modes of resistance were activated, while in others either mode dominated the resistance response. Cell wall-based resistance was common to all sorghum genotypes but strongest in IS2814, while a hypersensitive response was specific to N13, IS9830, and IS41724. WGCNA further allowed for pinpointing of S. hermonthica resistance causative genes in sorghum, including glucan synthase-like 10 gene, a pathogenesis-related thaumatin-like family gene, and a phosphoinositide phosphatase gene. Such candidate genes will form a good basis for subsequent functional validation and possibly future resistance breeding.

Development of Schizochytrium sp. strain HS01 with high-DHA and low-saturated fatty acids production by multi-pronged adaptive evolution.

PURPOSE: Docosahexaenoic acid (DHA) is an important omega-3 unsaturated fatty acid and has been widely applied in medicine, food additives, and feed ingredients. The fermentative production of DHA using microorganisms, including Schizochytrium sp., attracted much attention due to its high production efficiency and environment friendly properties. An efficient laboratory evolution approach was used to improve the strain's performance in this study. METHODS: A multi-pronged laboratory evolution approach was applied to evolve high-yield DHA-producing Schizochytrium strain. We further employed comparative transcriptional analysis to identify transcriptional changes between the screened strain HS01 and its parent strain GS00. RESULTS: After multiple generations of ALE, a strain HS01 with higher DHA content and lower saturated fatty acids content was obtained. Low nitrogen conditions were important for enhancing DHA biosynthesis in HS01. The comparative transcriptional analysis results indicated that during the fermentation process of HS01, the expression of key enzymes in the glycolysis, the pentose phosphate pathway and the tricarboxylic acid cycle were up-regulated, while the expression of polyketide synthase genes and fatty acid synthesis genes were similar to those in GS00. CONCLUSION: The results suggest that the improved DHA production capacity of HS01 is not due to enhancement of the DHA biosynthesis pathway, but rather related to modulation of central metabolism pathways.

Pheromone sensing in Drosophila requires support cell-expressed Osiris 8.

BACKGROUND: The nose of most animals comprises multiple sensory subsystems, which are defined by the expression of different olfactory receptor families. Drosophila melanogaster antennae contain two morphologically and functionally distinct subsystems that express odorant receptors (Ors) or ionotropic receptors (Irs). Although these receptors have been thoroughly characterized in this species, the subsystem-specific expression and roles of other genes are much less well-understood. RESULTS: Here we generate subsystem-specific transcriptomic datasets to identify hundreds of genes, encoding diverse protein classes, that are selectively enriched in either Or or Ir subsystems. Using single-cell antennal transcriptomic data and RNA in situ hybridization, we find that most neuronal genes-other than sensory receptor genes-are broadly expressed within the subsystems. By contrast, we identify many non-neuronal genes that exhibit highly selective expression, revealing substantial molecular heterogeneity in the non-neuronal cellular components of the olfactory subsystems. We characterize one Or subsystem-specific non-neuronal molecule, Osiris 8 (Osi8), a conserved member of a large, insect-specific family of transmembrane proteins. Osi8 is expressed in the membranes of tormogen support cells of pheromone-sensing trichoid sensilla. Loss of Osi8 does not have obvious impact on trichoid sensillar development or basal neuronal activity, but abolishes high sensitivity responses to pheromone ligands. CONCLUSIONS: This work identifies a new protein required for insect pheromone detection, emphasizes the importance of support cells in neuronal sensory functions, and provides a resource for future characterization of other olfactory subsystem-specific genes.