Comparative transcriptome analysis between rhesus macaques(Macaca mulatta) and crab-eating macaques(M. fascicularis)

Understanding gene expression variations between species is pivotal for deciphering the evolutionary diversity in phenotypes. Rhesus macaques(Macaca mulatta, MMU)and crab-eating macaques(M. fascicularis, MFA) serve as crucial nonhuman primate biomedical models with different phenotypes. To date, however, large-scale comparative transcriptome research between these two species has not yet been fully explored. Here, we conducted systematic comparisons utilizing newly sequenced RNA-seq data from84 samples(41 MFA samples and 43 MMU samples)encompassing 14 common tissues. Our findings revealed a small fraction of genes(3.7%) with differential expression between the two species, as well as 36.5% of genes with tissue-specific expression in both macaques. Comparison of gene expression between macaques and humans indicated that 22.6% of orthologous genes displayed differential expression in at least two tissues. Moreover,19.41% of genes that overlapped with macaque-specific structural variants showed differential expression between humans and macaques. Of these, the FAM220A gene exhibited elevated expression in humans compared to macaques due to lineage-specific duplication. In summary,this study presents a large-scale transcriptomic comparison between MMU and MFA and between macaques and humans. The discovery of gene expression variations not only enhances the biomedical utility of macaque models but also contributes to the wider field of primate genomics.

Comparative transcriptomes reveal the disjunction adaptive strategy of Thuja species in East Asia and North America

The genus Thuja is ideal for investigating the genetic basis of the East Asia-North America disjunction.The biogeographical background of the genus is debatable and an adaptive strategy is lacking.Through the analysis and mining of comparative transcriptomes,species differentiation and positively selected genes(PSGs)were identified to provide information for understanding the environmental adaptation strategies of the genus Thuja.De novo assembly yielded 44,397-74,252 unigenes of the five Thuja species with contig N50length ranging from 1,559 to 1,724 bp.Annotations revealed a similar distribution of functional categories among them.Based on the phylogenetic trees constructed using the transcriptome data,T.sutchuenensis was divided first,followed by T.plicata and T.occidentalis.The final differentiation of T.koraiensis and T.standishii formed a clade.Enrichment analysis indicated that the PSGs of the North American Thuja species were involved in plant hormone signal transduction and carbon fixation of photosynthetic organisms pathways.The PSGs of East Asian Thuja were related to phenolic,alkaloid,and terpenoid synthesis,important stress-resistant genes and could increase plant resistance to external environmental stresses.This study discovered numerous aroma synthetic-related PSGs including terpene synthase(TPS)genes and lipid phosphate phosphatase 2(LPP2),associated with the synthetic aroma of T.sutchuenensis.Physiological indicators,such as the contents of soluble sugars,total chlorophyll,total phenolics,and total flavonoids were determined,which are consistent with the PSGs enrichment pathways associated with adaptive strategies in the five Thuja species.The results of this study provide an important basis for future studies on conservation genetics.

Comparative transcriptome sequencing and weighted coexpression network analysis reveal growth-related hub genes and key pathways in the Chinese soft-shelled turtle(Pelodiscus sinensis)

The Chinese soft-shelled turtle(Pelodiscus sinensis)exhibits sexual dimorphism.Compared with females,males are considered to have higher economic value due to their accelerated growth,greater body mass,and longer skirt width.Studies focused on these sex disparities have largely neglected potential sex differences in growth.Here,we performed RNA sequencing of muscle tissue components from 1-year-old specimens to reveal gene expression patterns in P.sinensis.In our male and female cohorts,our analysis revealed,respectively,388 and 526 upregulated differentially expressed genes(DEGs)and 1129 and 635 downregulated DEGs.Through weighted coexpression network analysis(WGCNA)and integration with phenotype data,we established two main gene modules:a light yellow module encompassing 191 genes(e.g.,ACACB,CTH,HADHA,and CTNNB)that demonstrated a positive correlation with population traits,and a black module comprising 298 genes(e.g.,CAV3,PIK3CD,SMAD3,and VEGFA)that demonstrated a negative correlation with population traits.We also performed a DEG evaluation and gene set enrichment analysis across individuals of different sizes and noted that pathways such as protein digestion and assimilation(ko04974),were substantially augmented in larger specimens.In these pathways,the collagen(COL)and solute carrier(SLC)gene families were noted to be crucial for sustaining body structure and facilitating nutrient and metabolite transportation.In conclusion,we elucidated the essential modules,pivotal genes,and pathways involved in gene expression differences among various P.sinensis size groupings.Our results provide novel insights for future studies on growth discrepancies in P.sinensis.

Comparative transcriptome analysis between abundant and deficient spore strains provides novel insight into gene regulatory networks and mechanisms of monospore production in bladed Bangiales

As an important seedling source,monospores closely associate with yields in nori farming.However,the molecular mechanism underlying differences in monospore production for different strains remains unknown.Comparative transcriptome analysis was performed to examine gene expression differences between the spore abundant wild-type strain(WT)and spore deficient mutant(Y1)of Pyropia chauhanii.The WT strain that produces monospores in abundance exhibited more differentially expressed genes(DEGs)in both number and higher fold-changes than the Y1 strain incapable of producing monospores,indicating that the specific regulation of genes is involved in monospore production.Three lists of DEGs were obtained between the two strains using intersection and displayed in Venn diagram:one expressed only in WT strain,another expressed only in Y1 strain,and the third shared in both strains.DEGs annotated as homologous genes of Arabidopsis thaliana in these 3 lists were curated for online functional enrichment analysis on Metascape website.Gene regulatory networks of WT were functionally enriched in the processing,proteolysis,and transport of proteins,especially within the small GTPase protein family,which might be account for the monospore production ability,whereas Y1 were functionally enriched in the metabolism of essential substance and utilization of indispensable energy,which might be account for the rapid growth of blades.We found the differentially enriched gene regulatory networks between strains might be the intrinsic mechanisms of the different monospore production traits.These findings provide novel insights into the genes and regulatory networks associated with monospore production abilities,which are essential for developing accurate breeding technologies for optimal release of monospores and increase of total nori production.

Comparative transcriptomic analysis of Rosa sterilis inflorescence branches with different trichome types reveals an R3-MYB transcription factor that negatively regulates trichome formation

Rosa sterilis S.D.Shi is an important economic tree in China that produces fruits with high nutritional and medicinal value.Many of R.sterills’organs are covered with different types of trichomes or prickles that directly affect fruit appearance and plant management.This study used RNA sequencing technology to analyze the transcriptomes of two parts of the inflorescence branch,namely inflorescence stems with flagellated trichomes and pedicels with both flagellated and glandular trichomes.Comparative transcriptomic analysis showed that many transcription factors(TFs)are potentially involved in the formation and development of trichomes.The accumulation of RsETC1,a TF of the R3-MYB family,was significantly higher in inflorescence stems than in pedicels;quantitative reverse transcription PCR(qRTPCR)verified that its expression was significantly higher in inflorescence stems than in pedicels during the first three development stages,indicating its inhibitory action on the initiation of glandular trichomes in R.sterilis.The mRNA level of RsETC1 accumulated to significantly higher levels in trichomeless tissues than in tissues with trichromes,suggesting that this gene may inhibit the formation of trichomes in R.sterilis.Over-expression of RsETC1 in Arabidopsis resulted in glabrous phenotypes,and the expression of trichome-related endogenous genes,except for TTG1,was markedly reduced.In addition,the contents of the phytohormones jasmonic acid(JA),gibberellin A3(GA_(3)),and cytokinins(CKs)in pedicels were significantly higher than those in inflorescence stems,and the expression patterns of the genes related to hormone biosynthesis and signal transduction presented consistent responses,suggesting that the transduction of these hormones might be crucial for trichome initiation and development.These data provide a new perspective for revealing the molecular mechanism of trichome formation in R.sterilis.

Comparative transcriptomics reveals genes involved in metabolic and immune pathways in the digestive gland of scallop Chlamysfarreri following cadmium exposure

Chlamys farreri is an economically important mollusk that can accumulate excessive amounts of cadmium(Cd). Studying the molecular mechanism of Cd accumulation in bivalves is difficult because of the lack of genome background. Transcriptomic analysis based on high-throughput RNA sequencing has been shown to be an efficient and powerful method for the discovery of relevant genes in non-model and genome reference-free organisms. Here, we constructed two c DNA libraries(control and Cd exposure groups) from the digestive gland of C. farreri and compared the transcriptomic data between them. A total of 227 673 transcripts were assembled into 105 071 unigenes, most of which shared high similarity with sequences in the NCBI non-redundant protein database. For functional classification, 24 493 unigenes were assigned to Gene Ontology terms. Additionally, Eu Karyotic Ortholog Groups and Kyoto Encyclopedia of Genes and Genomes analyses assigned 12 028 unigenes to 26 categories and 7 849 unigenes to five pathways, respectively. Comparative transcriptomics analysis identified 3 800 unigenes that were differentially expressed in the Cd-treated group compared with the control group. Among them, genes associated with heavy metal accumulation were screened, including metallothionein, divalent metal transporter, and metal tolerance protein. The functional genes and predicted pathways identified in our study will contribute to a better understanding of the metabolic and immune system in the digestive gland of C. farreri. In addition, the transcriptomic data will provide a comprehensive resource that may contribute to the understanding of molecular mechanisms that respond to marine pollutants in bivalves.

De novo assembly and comparative analysis of root transcriptomes from different varieties of Panax ginseng C. A. Meyer grown in different environments

Panax ginseng C. A. Meyer is an important traditional herb in eastern Asia. It contains ginsenosides, which are primary bioactive compounds with medicinal properties. Although ginseng has been cultivated since at least the Ming dynasty to increase production, cultivated ginseng has lower quantities of ginsenosides and lower disease resistance than ginseng grown under natural conditions. We extracted root RNA from six varieties of fifth-year P. ginseng cultivars representing four different growth conditions, and performed Illumina paired-end sequencing. In total, 163,165,706 raw reads were obtained and used to generate a de novo transcriptome that consisted of 151,763 contigs(76,336 unigenes), of which 100,648 contigs(66.3%) were successfully annotated. Differential expression analysis revealed that most differentially expressed genes(DEGs) were upregulated(246 out of 258, 95.3%) in ginseng grown under natural conditions compared with that grown under artificial conditions. These DEGs were enriched in gene ontology(GO) terms including response to stimuli and localization. In particular, some key ginsenoside biosynthesis-related genes, including HMG-Co A synthase(HMGS), mevalonate kinase(MVK), and squalene epoxidase(SE), were upregulated in wild-grown ginseng. Moreover, a high proportion of disease resistance-related genes were upregulated in wild-grown ginseng. This study is the first transcriptome analysis to compare wild-grown and cultivated ginseng, and identifies genes that may produce higher ginsenoside content and better disease resistance in the wild; these genes may have the potential to improve cultivated ginseng grown in artificial environments.

Comparative transcriptomics revealed enhanced light responses, energy transport and storage in domestication of cassava(Manihot esculenta)

Cassava is a staple food, feed and bioenergy crop important to the world especially in the tropics.Domesticated cassava is characterized by powerful carbohydrate accumulation but its wild progenitor is not.Here, we investigated the transcriptional differences of eight c DNA libraries derived from developing leaf, stem and storage root of cassava cv. Arg7 and an ancestor line,W14, using next generation sequencing system. A total of41302 assembled transcripts were obtained and from these,25961 transcripts with FPKM≥3 in at least one library were named the expressed genes. A total of 2117, 1963 and3584 transcripts were found to be differentially expressed in leaf, stem and storage root(150 d after planting),respectively, between Arg7 and W14 and ascribed to 103,93 and 119 important pathways in leaf, stem and storage root, respectively. The highlight of this work is that the genes involved in light response, such as those for photosystem I(PSA) and photosystem II(PSB), other genes involved in light harvesting, and some of the genes in the Calvin cycle of carbon fixation were specially upregulated in leaf. Genes for transport and also for key rate-limiting enzymes(PFK, PGK and PK, GAPDH)coupling ATP consumption in glycolysis pathway were predominantly expressed in stem, and genes for sucrose degradation(INVs), amylose synthesis(GBSS) and hydrolysis(RCP1, AMYs), the three key steps of starch metabolism, and transport associated with energy translocation(ABC, AVPs and ATPase) and their upstream transcription factors had enhanced expression in storage root in domesticated cassava. Co-expression networks among the pathways in each organs revealed therelationship of the genes involved, and uncovered some of the important hub genes and transcription factors targeting genes for photosynthesis, transportation and starch biosynthesis.

Comparative transcriptomic insights into the mechanisms of electron transfer in Geobacter co-cultures with activated carbon and magnetite

Both activated carbon and magnetite have been reported to promote the syntrophic growth of Geobacter metallireducens and Geobacter sulfurreducens co-cultures, the first model to show direct interspecies electron transfer (DIET); however, differential transcriptomics of the promotion on co-cultures with these two conductive materials are unknown. Here, the comparative transcriptomic analysis of G. metallireducens and G. sulfurreducens co-cultures with granular activated carbon (GAC) and magnetite was reported. More than 2.6-fold reduced transcript abundances were determined for the uptake hydrogenase genes of G. sulfurreducens as well as other hydrogenases in those co-cultures to which conductive materials had been added. This is consistent with electron transfer in G. metallireducens-G. sulfurreducens co-cultures as evinced by direct interspecies electron transfer (DIET). Transcript abundance for the structural component of electrically conductive pili (e-pili), PilA, was 2.2-fold higher in G. metallireducens, and, in contrast, was 14.9-fold lower in G. sulfurreducens in co-cultures with GAC than in Geobacters co-cultures without GAC. However, it was 9.3-fold higher in G. sulfurreducens in co-cultures with magnetite than in Geobacters co-cultures. Mutation results showed that GAC can be substituted for the e-pili of both strains but magnetite can only compensate for that of G. sulfurreducens, indicating that the e-pili is a more important electron acceptor for the electron donor strain of G. metallireducens than for G. sulfurreducens. Transcript abundance for G. metallireducens c-type cytochrome gene GMET_RS14535, a homologue to c-type cytochrome gene omcE of G. sulfurreducens was 9.8-fold lower in co-cultures with GAC addition, while that for OmcS of G. sulfurreducens was 25.1-fold higher in co-cultures with magnetite, than in that without magnetite. Gene deletion studies showed that neither GAC nor magnetite can completely substitute the cytochrome (OmcE homologous) of G. metallireducens but compensate for the cytochrome (OmcS) of G. sulfurreducens. Moreover, some genes associated with central metabolism were up-regulated in the presence of both GAC and magnetite; however, tricarboxylic acid cycle gene transcripts in G. sulfurreducens were not highly-expressed in each of these amended co-cultures, suggesting that there was considerable redundancy in the pathways utilised by G. sulfurreducens for electron transfer to reduce fumarate with the amendment of GAC or magnetite. These results support the DIET model of G. metallireducens and G. sulfurreducens and suggest that e-pili and cytochromes of the electron donor strain are more important than that of the electron acceptor strain, indicating that comparative transcriptomics may be a promising route by which to reveal different responses of electron donor and acceptor during DIET in co-cultures.

Comparative transcriptomics reveals hidden issues in the plant response to arthropod herbivores

Plants experience different abiotic/biotic stresses,which trigger their molecular machinery to cope with them. Besides general mechanisms prompted by many stresses, specific mechanisms have been introduced to optimize the response to individual threats. However, these key mechanisms are difficult to identify. Here, we introduce an in-depth species-specific transcriptomic analysis and conduct an extensive meta-analysis of the responses to related species to gain more knowledge about plant responses. The spider mite Tetranychus urticae was used as the individual species, several arthropod herbivores as the related species for meta-analysis, and Arabidopsis thaliana plants as the common host. The analysis of the transcriptomic data showed typical common responses to herbivory, such as jasmonate signaling or glucosinolate biosynthesis. Also, a specific set of genes likely involved in the particularities of the Arabidopsis-spider mite interaction was discovered. The new findings have determined a prominent role in this interaction of the jasmonateinduced pathways leading to the biosynthesis of anthocyanins and tocopherols. Therefore, tandem individual/general transcriptomic profiling has been revealed as an effective method to identify novel relevant processes and specificities in the plant response to environmental stresses.

Global regulation of fungal secondary metabolism in Trichoderma reesei by the transcription factor Ypr1,as revealed by transcriptome analysis

Trichoderma reesei Rut-C-30 is a well-known robust producer of cellulolytic enzymes,which are used to degrade lignocellulosic biomass for the sustainable production of biofuels and biochemicals.However,studies of its sec-ondary metabolism and regulation remain scarce.Ypr1 was previously described as a regulator of the biosynthesis of the yellow pigment sorbicillin(a bioactive agent with great pharmaceutical interest)in T.reesei and several other fungi.However,the manner in which this regulator affects global gene transcription has not been explored.In this study,we report the effect of Ypr1 on the regulation of both the secondary and primary metabolism of T.reesei Rut-C30.A global gene transcription profile was obtained using a comparative transcriptomic analysis of the wild-type strain T.reesei Rut-C-30 and its ypr1 deletion mutant.The results of this analysis suggest that,in addition to its role in regulating sorbicillin and the major extracellular(hemi)cellulases,Ypr1 also affects the transcription of genes encoding several other secondary metabolites.Although the primary metabolism of T.reeseiΔypr1 became less active compared with that of T.reesei Rut-C-30,several gene clusters involved in its secondary metabolism were activated,such as the gene clusters for the biosynthesis of specific polyketides and non-ribosomal peptides,together with the“sorbicillinoid-cellulase”super cluster,indicating that specific secondary metabolites and cellulases may be co-regulated in T.reesei Rut-C-30.The results presented in this study may benefit the development of genetic engineering strategies for the production of sorbicillin by T.reesei Rut-C-30,and provide insights for enhancing sorbicillin production in other filamentous fungal producers.

Modes of genetic adaptations underlying functional innovations in the rumen

The rumen is the hallmark organ of ruminants and hosts a diverse ecosystem of microorganisms that facilitates efficient digestion of plant fibers.We analyzed 897 transcriptomes from three Cetartiodactyla lineages:ruminants,camels and cetaceans,as well as data from ruminant comparative genomics and functional assays to explore the genetic basis of rumen functional innovations.We identified genes with relatively high expression in the rumen,of which many appeared to be recruited from other tissues.These genes show functional enrichment in ketone body metabolism,regulation of microbial community,and epithelium absorption,which are the most prominent biological processes involved in rumen innovations.Several modes of genetic change underlying rumen functional innovations were uncovered,including coding mutations,genes newly evolved,and changes of regulatory elements.We validated that the key ketogenesis rate-limiting gene(HMGCS2)with five ruminant-specific mutations was under positive selection and exhibits higher synthesis activity than those of other mammals.Two newly evolved genes(LYZ1 and DEFB1)are resistant to Gram-positive bacteria and thereby may regulate microbial community equilibrium.Furthermore,we confirmed that the changes of regulatory elements accounted for the majority of rumen gene recruitment.These results greatly improve our understanding of rumen evolution and organ evo-devo in general.

Integrating Genomic and Transcriptomic Data to Reveal Genetic Mechanisms Underlying Piao Chicken Rumpless Trait

Piao chicken,a rare Chinese native poultry breed,lacks primary tail structures,such as pygostyle,caudal vertebra,uropygial gland,and tail feathers.So far,the molecular mechanisms underlying tail absence in this breed remain unclear.In this study,we comprehensively employed comparative transcriptomic and genomic analyses to unravel potential genetic underpinnings of rumplessness in Piao chicken.Our results reveal many biological factors involved in tail development and several genomic regions under strong positive selection in this breed.These regions contain candidate genes associated with rumplessness,including Irx4,Il18,Hspb2,and Cryab.Retrieval of quantitative trait loci(QTL)and gene functions implies that rumplessness might be consciously or unconsciously selected along with the high-yield traits in Piao chicken.We hypothesize that strong selection pressures on regulatory elements might lead to changes in gene activity in mesenchymal stem cells of the tail bud.The ectopic activity could eventually result in tail truncation by impeding differentiation and proliferation of the stem cells.Our study provides fundamental insights into early initiation and genetic basis of the rumpless phenotype in Piao chicken.

Exploiting plant transcriptomic databases:Resources,tools,and approaches

There are now more than 300000 RNA sequencing samples available,stemming from thousands of exper-iments capturing gene expression in organs,tissues,developmental stages,and experimental treatments for hundreds of plant species.The expression data have great value,as they can be re-analyzed by others to ask and answer questions that go beyond the aims of the study that generated the data.Because gene expression provides essential clues to where and when a gene is active,the data provide powerful tools for predicting gene function,and comparative analyses allow us to study plant evolution from a new perspective.This review describes how we can gain new knowledge from gene expression profiles,expres-sion specificities,co-expression networks,differential gene expression,and experiment correlation.We also introduce and demonstrate databases that provide user-friendly access to these tools.