Meta-analysis of drought-tolerant genotypes in Oryza sativa: A network-based approach

Dissection of QTLs underlying the genetic basis of drought resistance in wheat: a meta-analysis

Wheat (Triticum aestivum L.) is one of the most important cereal crops, with its grain serving as a predominant staple food source on a global scale. However, there are many biotic and abiotic stresses challenging the stability of wheat production. Among the abiotic stresses, drought is recognized as a significant stress and poses a substantial threat to food production and quality throughout the world. Raising drought tolerance of wheat varieties through genetic regulation is therefore considered as one of the most effective ways to combat the challenges caused by drought stress. Meta-QTL analysis has demonstrated its effectiveness in identifying consensus QTL regions in wheat drought resistance in numerous instances. In this study, we present a comprehensive meta-analysis aimed at unraveling the drought tolerance genetic basis associated with agronomic traits in bread wheat. Extracting data from 34 previously published studies, we aggregated a corpus of 1291 Quantitative Trait Loci (QTL) pertinent to wheat drought tolerance. Then, the translation of the consensus genetic map yielded a comprehensive compendium of 49 distinct MQTLs, each associated with diverse agronomic traits. Prominently featured among the MQTLs were MQTLs 1.1, 1.7, 1.8 (1D), 4.1 (4A), 4.6 (4D), 5.2 (5B), 6.6 (6B), and 7.2 (7B), distinguished as pivotal MQTLs offering significant potential for application in marker-assisted breeding endeavors. Altogether, a total of 66 putative candidate genes (CGs)-related drought tolerance were identified. This work illustrates a translational research approach in transferring information from published mapping studies to genomic regions hosting major QTLs governing key agronomical traits in wheat.

Drought-induced molecular changes in crown of various barley phytohormone mutants

One of the main signal transduction pathways that modulate plant growth and stress responses, including drought, is the action of phytohormones. Recent advances in omics approaches have facilitated the exploration of plant genomes. However, the molecular mechanisms underlying the response in the crown of barley, which plays an essential role in plant performance under stress conditions and regeneration after stress treatment, remain largely unclear. The objective of the present study was the elucidation of drought-induced molecular reactions in the crowns of different barley phytohormone mutants. We verified the hypothesis that defects of gibberellins, brassinosteroids, and strigolactones action affect the transcriptomic, proteomic, and hormonal response of barley crown to the transitory drought influencing plant development under stress. Moreover, we assumed that due to the strong connection between strigolactones and branching the hvdwarf14.d mutant, with dysfunctional receptor of strigolactones, manifests the most abundant alternations in crowns and phenotype under drought. Finally, we expected to identify components underlying the core response to drought which are independent of the genetic background. Large-scale analyses were conducted using gibberellins-biosynthesis, brassinosteroids-signaling, and strigolactones-signaling mutants, as well as reference genotypes. Detailed phenotypic evaluation was also conducted. The obtained results clearly demonstrated that hormonal disorders caused by mutations in the HvGA20ox2, HvBRI1, and HvD14 genes affected the multifaceted reaction of crowns to drought, although the expression of these genes was not induced by stress. The study further detected not only genes and proteins that were involved in the drought response and reacted specifically in mutants compared to the reaction of reference genotypes and vice versa, but also the candidates that may underlie the genotype-universal stress response. Furthermore, candidate genes involved in phytohormonal interactions during the drought response were identified. We also found that the interplay between hormones, especially gibberellins and auxins, as well as strigolactones and cytokinins may be associated with the regulation of branching in crowns exposed to drought. Overall, the present study provides novel insights into the molecular drought-induced responses that occur in barley crowns.

Genome-Wide Identification, Characterization and Expression Patterns of the DBB Transcription Factor Family Genes in Wheat

Double B-box (DBB) proteins are plant-specific transcription factors (TFs) that play crucial roles in plant growth and stress responses. This study investigated the classification, structure, conserved motifs, chromosomal locations, cis-elements, duplication events, expression levels, and protein interaction network of the DBB TF family genes in common wheat (Triticum aestivum L.). In all, twenty-seven wheat DBB genes (TaDBBs) with two conserved B-box domains were identified and classified into six subgroups based on sequence features. A collinearity analysis of the DBB family genes among wheat, Arabidopsis, and rice revealed some duplicated gene pairs and highly conserved genes in wheat. An expression pattern analysis indicated that wheat TaDBBs were involved in plant growth, responses to drought stress, light/dark, and abscisic acid treatment. A large number of cis-acting regulatory elements related to light response are enriched in the predicted promoter regions of 27 TaDBBs. Furthermore, some of TaDBBs can interact with COP1 or HY5 based on the STRING database prediction and yeast two-hybrid (Y2H) assay, indicating the potential key roles of TaDBBs in the light signaling pathway. Conclusively, our study revealed the potential functions and regulatory mechanisms of TaDBBs in plant growth and development under drought stress, light, and abscisic acid.

Flexibility of parental-like or maternal-like gene expression under diverse environments contributes to combined drought avoidance and drought tolerance in a water-saving and drought-resistance rice hybrid

KEY MESSAGE

The hybrid rice variety (Hanyou73) exhibits the maternal-like (HH7A) gene expression in roots and parental-like (HH3) gene expression in leaves to obtain both advantages of drought avoidance and drought tolerance from its two parents.

BACKGROUND

Rice is one of the most important crops in the world. Rice production consumes lots of water and significantly suffers from the water deficiency and drought stress. The water-saving and drought-resistance rice (WDR) confers good drought resistance and performs well in the water-saving cultivation.

MAIN FINDINGS

A hybrid WDR variety Hanyou73 (HY73) exhibited superior drought resistance compared with its parents Hanhui3 (HH3) and Huhan7A (HH7A). Studies on drought resistance related traits revealed that HY73 performed like HH3 and HH7A on drought tolerance and drought avoidance, respectively. Transcriptomes were analyzed for samples with various phytohormone treatments and abiotic stresses, in which HY73 was closer to HH3 in leaf samples while HH7A in root samples. HY73 and its parents differed largely in DEGs and GO analysis for DEGs suggested the different pathways of drought response in HH3 and HH7A. Parent-like expression analysis revealed that the higher-parent-like expression pattern was prevailing in HY73. In addition, patterns of the parent-like expression significantly transformed between abiotic-stressed/phytohormone-treated and control samples, which might help HY73 to adapt to different environments. WGCNA analysis for those parent-like expression genes revealed some drought resistant genes that should contribute to the superior drought resistance of HY73. Genetic variation on the promotor sequence was confirmed as the reason for the flexible parent-like gene expression in HY73.

CONCLUSION

Our study uncovered the important roles of complementation of beneficial traits from parents and flexible gene expressions in drought resistance of HY73, which could facilitate the development of new WDR varieties.

Genome-Wide Association Study of Early Vigour-Related Traits for a Rice (Oryza sativa L.) japonica Diversity Set Grown in Aerobic Conditions

Aerobic rice production is a relatively new system in which rice is direct-seeded and grown in non-flooded but well-watered conditions to improve water productivity. Early vigour-related traits are likely to be important in aerobic conditions. This study aimed to identify quantitative trait loci (QTL) and candidate genes associated with early vigour-related traits in aerobic conditions using a japonica rice diversity set. Field experiments and glasshouse experiments conducted under aerobic conditions revealed significant genotypic variation in early vigour-related traits. Genome-wide association analysis identified 32 QTL associated with early vigour-related traits. Notably, two QTL, qAEV1.5 and qAEV8, associated with both early vigour score and mesocotyl length, explained up to 22.1% of the phenotypic variance. In total, 23 candidate genes related to plant growth development and abiotic stress response were identified in the two regions. This study provides novel insights into the genetic basis of early vigour under aerobic conditions. Validation of identified QTL and candidate genes in different genetic backgrounds is crucial for future studies. Moreover, testing the effect of QTL on yield under different environments would be valuable. After validation, these QTL and genes can be considered for developing markers in marker-assisted selection for aerobic rice production.

Identification of Key Gene Network Modules and Hub Genes Associated with Wheat Response to Biotic Stress Using Combined Microarray Meta-analysis and WGCN Analysis

Wheat (Triticum aestivum) is one of the major crops worldwide and a primary source of calories for human food. Biotic stresses such as fungi, bacteria, and diseases limit wheat production. Although plant breeding and genetic engineering for biotic stress resistance have been suggested as promising solutions to handle losses caused by biotic stress factors, a comprehensive understanding of molecular mechanisms and identifying key genes is a critical step to obtaining success. Here, a network-based meta-analysis approach based on two main statistical methods was used to identify key genes and molecular mechanisms of the wheat response to biotic stress. A total of 163 samples (21,792 genes) from 10 datasets were analyzed. Fisher Z test based on the p-value and REM method based on effect size resulted in 533 differentially expressed genes (p < 0.001 and FDR < 0.001). WGCNA analysis using a dynamic tree-cutting algorithm was used to construct a co-expression network and three significant modules were detected. The modules were significantly enriched by 16 BP terms and 4 KEGG pathways (Benjamini-Hochberg FDR < 0.001). A total of nine hub genes (a top 1.5% of genes with the highest degree) were identified from the constructed network. The identification of DE genes, gene-gene co-expressing network, and hub genes may contribute to uncovering the molecular mechanisms of the wheat response to biotic stress.

Identification of key genes involved in secondary metabolite biosynthesis in Digitalis purpurea

The medicinal plant Digitalis purpurea produces cardiac glycosides that are useful in the pharmaceutical industry. These bioactive compounds are in high demand due to ethnobotany's application to therapeutic procedures. Recent studies have investigated the role of integrative analysis of multi-omics data in understanding cellular metabolic status through systems metabolic engineering approach, as well as its application to genetically engineering metabolic pathways. In spite of numerous omics experiments, most molecular mechanisms involved in metabolic pathways biosynthesis in D. purpurea remain unclear. Using R Package Weighted Gene Co-expression Network Analysis, co-expression analysis was performed on the transcriptome and metabolome data. As a result of our study, we identified transcription factors, transcriptional regulators, protein kinases, transporters, non-coding RNAs, and hub genes that are involved in the production of secondary metabolites. Since jasmonates are involved in the biosynthesis of cardiac glycosides, the candidate genes for Scarecrow-Like Protein 14 (SCL14), Delta24-sterol reductase (DWF1), HYDRA1 (HYD1), and Jasmonate-ZIM domain3 (JAZ3) were validated under methyl jasmonate treatment (MeJA, 100 μM). Despite early induction of JAZ3, which affected downstream genes, it was dramatically suppressed after 48 hours. SCL14, which targets DWF1, and HYD1, which induces cholesterol and cardiac glycoside biosynthesis, were both promoted. The correlation between key genes and main metabolites and validation of expression patterns provide a unique insight into the biosynthesis mechanisms of cardiac glycosides in D. purpurea.

NetREx: Network-based Rice Expression Analysis Server for abiotic stress conditions

Recent focus on transcriptomic studies in food crops like rice, wheat and maize provide new opportunities to address issues related to agriculture and climate change. Re-analysis of such data available in public domain supplemented with annotations across molecular hierarchy can be of immense help to the plant research community, particularly co-expression networks representing transcriptionally coordinated genes that are often part of the same biological process. With this objective, we have developed NetREx, a Network-based Rice Expression Analysis Server, that hosts ranked co-expression networks of Oryza sativa using publicly available messenger RNA sequencing data across uniform experimental conditions. It provides a range of interactable data viewers and modules for analysing user-queried genes across different stress conditions (drought, flood, cold and osmosis) and hormonal treatments (abscisic and jasmonic acid) and tissues (root and shoot). Subnetworks of user-defined genes can be queried in pre-constructed tissue-specific networks, allowing users to view the fold change, module memberships, gene annotations and analysis of their neighbourhood genes and associated pathways. The web server also allows querying of orthologous genes from Arabidopsis, wheat, maize, barley and sorghum. Here, we demonstrate that NetREx can be used to identify novel candidate genes and tissue-specific interactions under stress conditions and can aid in the analysis and understanding of complex phenotypes linked to stress response in rice. Database URL: https://bioinf.iiit.ac.in/netrex/index.html.

Rice and Arabidopsis BBX proteins: toward genetic engineering of abiotic stress resistant crops

Productivity of crop plants are enormously affected by biotic and abiotic stresses. The co-occurrence of several abiotic stresses may lead to death of crop plants. Hence, it is the responsibility of plant scientists to develop crop plants equipped with multistress tolerance pathways. A subgroup of zinc finger transcription factor family, known as B-box (BBX) proteins, play a key role in light and hormonal regulation pathways. In addition, BBX proteins act as key regulatory proteins in many abiotic stress regulatory pathways, including Ultraviolet-B (UV-B), salinity, drought, heat and cold, and heavy metal stresses. Most of the BBX proteins identified in Arabidopsis and rice respond to more than one abiotic stress. Considering the requirement of improving rice for multistress tolerance, this review discusses functionally characterized Arabidopsis and rice BBX proteins in the development of abiotic stress responses. Furthermore, it highlights the participation of BBX proteins in multistress regulation and crop improvement through genetic engineering.

Gene Co-Expression Network Tools and Databases for Crop Improvement

Transcriptomics has significantly grown as a functional genomics tool for understanding the expression of biological systems. The generated transcriptomics data can be utilised to produce a gene co-expression network that is one of the essential downstream omics data analyses. To date, several gene co-expression network databases that store correlation values, expression profiles, gene names and gene descriptions have been developed. Although these resources remain scattered across the Internet, such databases complement each other and support efficient growth in the functional genomics area. This review presents the features and the most recent gene co-expression network databases in crops and summarises the present status of the tools that are widely used for constructing the gene co-expression network. The highlights of gene co-expression network databases and the tools presented here will pave the way for a robust interpretation of biologically relevant information. With this effort, the researcher would be able to explore and utilise gene co-expression network databases for crops improvement.

Candidate Genes and Pathways in Rice Co-Responding to Drought and Salt Identified by gcHap Network

Drought and salinity stresses are significant abiotic factors that limit rice yield. Exploring the co-response mechanism to drought and salt stress will be conducive to future rice breeding. A total of 1748 drought and salt co-responsive genes were screened, most of which are enriched in plant hormone signal transduction, protein processing in the endoplasmic reticulum, and the MAPK signaling pathways. We performed gene-coding sequence haplotype (gcHap) network analysis on nine important genes out of the total amount, which showed significant differences between the Xian/indica and Geng/japonica population. These genes were combined with related pathways, resulting in an interesting mechanistic draft called the ‘gcHap-network pathway’. Meanwhile, we collected a lot of drought and salt breeding varieties, especially the introgression lines (ILs) with HHZ as the parent, which contained the above-mentioned nine genes. This might imply that these ILs have the potential to improve the tolerance to drought and salt. In this paper, we focus on the relationship of drought and salt co-response gene gcHaps and their related pathways using a novel angle. The haplotype network will be helpful to explore the desired haplotypes that can be implemented in haplotype-based breeding programs.

A Comparative Transcriptomic Meta-Analysis Revealed Conserved Key Genes and Regulatory Networks Involved in Drought Tolerance in Cereal Crops

Drought affects plant growth and development, causing severe yield losses, especially in cereal crops. The identification of genes involved in drought tolerance is crucial for the development of drought-tolerant crops. The aim of this study was to identify genes that are conserved key players for conferring drought tolerance in cereals. By comparing the transcriptomic changes between tolerant and susceptible genotypes in four Gramineae species, we identified 69 conserved drought tolerant-related (CDT) genes that are potentially involved in the drought tolerance of all of the analysed species. The CDT genes are principally involved in stress response, photosynthesis, chlorophyll biogenesis, secondary metabolism, jasmonic acid signalling, and cellular transport. Twenty CDT genes are not yet characterized and can be novel candidates for drought tolerance. The k-means clustering analysis of expression data highlighted the prominent roles of photosynthesis and leaf senescence-related mechanisms in differentiating the drought response between tolerant and sensitive genotypes. In addition, we identified specific transcription factors that could regulate the expression of photosynthesis and leaf senescence-related genes. Our analysis suggests that the balance between the induction of leaf senescence and maintenance of photosynthesis during drought plays a major role in tolerance. Fine-tuning of CDT gene expression modulation by specific transcription factors can be the key to improving drought tolerance in cereals.

Stress memory of physiological, biochemical and metabolomic responses in two different rice genotypes under drought stress: The scale matters

Drought is a pivotal cause for crop yield reductions. When subjected to recurrent external stimuli, plants can develop memory of stress responses that, eventually, enables improved plant tolerance to environmental changes. In addition, despite causal relationships, these responses may vary according to hierarchical levels of observation. Thus, this study aims to check the responses of recurrent and non-recurrent stresses in two rice genotypes observing their drought memory responses at different levels of organization, that is, on a physiological, biochemical and metabolomic scale and for end in global PCA. For this, seventy variables were measured on the scales described in order to obtain a large number of observations. The memory responses were evident in almost all scales observed. The lowland genotype, especially plants not subjected to recurrent water shortage, showed higher damage to the photosynthetic apparatus under drought conditions, although it has exhibited more evident memory response effect after rehydration. On the other hand, the upland genotype appears to be more tolerant to drought insofar lower biochemical damage was observed. Specific behaviors of each genotype at biochemical and metabolomics levels and similar behavior at physiological level were observed. This study demonstrates the importance of observation at different hierarchical levels.

Metabolome profiling reveals impact of water limitation on grain filling in contrasting rice genotypes

Drought significantly decreases crop productivity, especially in high water consuming crops like rice. Grain filling is one of the important critical growth phases in rice and drought during this phase leads to significant reduction in yield. In this study, a comparison was made between IR64 (drought susceptible) and Apo (drought tolerant) rice genotypes to capture the response to water limitation (50% field capacity (FC)) compared with the control (100%FC) during grain filling. Plants were grown in a high-throughput phenomics facility for precise imposition of moisture stress during grain filling. Apo performed better in water limited conditions with lower reduction of photosynthetic rate and maintenance of lower leaf temperature than IR64. Days from sowing to maturity, spikelet fertility and seed weight were more impeded by water limitation in IR64 than in Apo. Unlike Apo, IR64 did not show any decrease in transpiration rate at 50%FC compared with 100%FC. Metabolomic profiling of spikelets at grain filling showed distinct effects of water limitation on accumulation of metabolites, especially in Apo. Secondary metabolism, mainly the phenylpropanoid pathway involved in scavenging mechanisms, was upregulated in Apo. Accumulation of most amino acids was significantly higher in IR64 than in Apo. Due to higher rates of photosynthesis under stress, most carbohydrates accumulated more in Apo than in IR64 at 50%FC. Sucrose transporters were significantly upregulated in water limited conditions especially in Apo. Overall, thanks to higher source capacity, more source to sink transport and better scavenging, Apo showed a lower reduction in yield than IR64.

Dynamics of cell wall structure and related genomic resources for drought tolerance in rice

Cell wall plasticity plays a very crucial role in vegetative and reproductive development of rice under drought and is a highly potential trait for improving rice yield under drought. Drought is a major constraint in rice (Oryza sativa L.) cultivation severely affecting all developmental stages, with the reproductive stage being the most sensitive. Rice plants employ multiple strategies to cope with drought, in which modification in cell wall dynamics plays a crucial role. Over the years, significant progress has been made in discovering the cell wall-specific genomic resources related to drought tolerance at vegetative and reproductive stages of rice. However, questions remain about how the drought-induced changes in cell wall made by these genomic resources potentially influence the vegetative and reproductive development of rice. The possibly major candidate genes underlying the function of quantitative trait loci directly or indirectly associated with the cell wall plasticization-mediated drought tolerance of rice might have a huge promise in dissecting the putative genomic regions associated with cell wall plasticity under drought. Furthermore, engineering the drought tolerance of rice using cell wall-related genes from resurrection plants may have huge prospects for rice yield improvement. Here, we review the comprehensive multidisciplinary analyses to unravel different components and mechanisms involved in drought-induced cell wall plasticity at vegetative and reproductive stages that could be targeted for improving rice yield under drought.

Differential adaptation strategies to different levels of soil water deficit in two upland and lowland genotypes of rice: a physiological and metabolic approach

BACKGROUND

Upland genotypes of rice are less sensitive to soil water deficit (SWD), making them suitable candidates for revealing the strategies underlying plant tolerance. The physiological factors, the biochemical traits needed to withstand oxidative stress, and the metabolite fluctuations of an upland genotype (Azucena) and an intolerant lowland genotype (IR64) genotype were measured under two levels of SWD (withholding water for 7- or 14 days) to identify SWD-responsive strategies associated with tolerance.

RESULTS

After withholding water for 7 days, no significant changes in physiological and biochemical traits of Azucena were observed, whereas in IR64, significant decreases in physiological factors were recorded along with increases in oxidative-stress indicators. However, the root length of Azucena increased significantly, showing a clear stress avoidance strategy. Under a prolonged treatment (14 days), IR64 entered an oxidative-damage stage, whereas Azucena exhibited a highly efficient antioxidant system. Our metabolite analysis also revealed two different enriched pathways. After a 7-day SWD, the sugar levels were decreased in the leaves of Azucena but increased in IR64. The reduction in the sugar levels (up to 1.79-log2FC) in the Azucena leaves may be indicative of their transport to the roots, supplying the carbon source needed for root elongation. Under a 14-day treatment, proline and aspartate family members accumulated to the highest levels in Azucena, whereas an increase in the levels of aromatic amino acids with key roles in the biosynthesis of secondary metabolites was detected in IR64.

CONCLUSION

The adaptation strategies identified in two types of rice genotypes in confronting SWD may assist researchers in finding the proper indicators for screening more tolerant genotypes. © 2019 Society of Chemical Industry.

Physiological, biochemical and gene-expressional responses to water deficit in apple subjected to partial root-zone drying (PRD)

Water scarcity is one of the major factors limiting apple production. Partial root-zone drying (PRD) is a water-saving irrigation technique necessary to improve the efficiency of irrigation techniques to optimize the amount of fruit produced with the volume of water used. The apple trees cv. Red Delicious were exposed to four treatments, including (1) control with 100% of the crop evapotranspiration (ETc) needs; (2) alternate partial root-zone drying with 75% of the ETc needs (APRD75); (3) fixed partial root-zone drying with 75% of the ETc needs (FPRD75); (4) fixed partial root-zone irrigation with 50% of the ETc needs (FPRD50) in a semiarid region of Iran. Results showed that leaf water potential (Ψ _leaf), and chlorophyll were significantly decreased in FPRD50 compared to control and other PRD treatments. APRD75 and FPRD75 treatments significantly enhanced (+) -catechin (+C), epicatechin (EC), chlorogenic acid (CGA), caffeic acid (CA) as well as increased water use efficiency (WUE) (by 30-40% compared to control) without significant reduction of yield. PRD reduced gibberellic acid (GA3) and kinetin, while, increased the abscisic acid (ABA) and salicylic acid (SA) levels. The abiotic stress-responsive transcription factors (TFs) MdoMYB121, MdoMYB155, MdbZIP2, and MdbZIP48 were highly expressed in all PRD treatments. Our results demonstrated that APRD75 and FPRD75 have the potential to stimulate antioxidant defense mechanisms, hormonal signaling pathways, and expression of drought-tolerance TFs to improve WUE while maintaining crop yield. Therefore, APRD75andFPRD75 with water savings as compared to full irrigation might be a suitable strategy for irrigation apple trees under water scarcity.

Functional Relevance of Citrulline in the Vegetative Tissues of Watermelon During Abiotic Stresses

A non-protein amino acid, citrulline, is a compatible solute involved in the maintenance of cellular osmolarity during abiotic stresses. Despite its significance, a coherent model indicating the role of citrulline during stress conditions has not yet emerged. We have used watermelon, naturally rich in citrulline, as a model to understand its accumulation during drought stress and nitrogen perturbation using transcriptomic and metabolomic analysis. Experiments were performed in the semi-controlled environment, and open field to study the accumulation of drought-induced citrulline in the vegetative tissues of watermelon by monitoring the stress treatments using physiological measurements. The amino acid profiling of leaves and stems in response to drought stress showed up to a 38 and 16-fold increase in citrulline content, respectively. Correlation between amino acids indicated a concomitant activation of a metabolic pathway that included citrulline, its precursor (ornithine), and catabolic product (arginine). Consistent with its accumulation, the gene expression analysis and RNA-Sequencing confirmed activation of citrulline biosynthesis-related genes - Ornithine carbamoyl-transferase (OTC), N-acetylornithine deacetylase (AOD) and Carbamoyl phosphate synthases (CPS), and down-regulation of catabolic genes; Arginosuccinate lyase (ASL) and Arginosuccinate synthases (ASS) in drought-stressed leaf tissues. Based on the relative abundance in the nitrogen-depleted vegetative tissues and down-regulation of genes involved in citrulline biosynthesis, we also demonstrated that the nitrogen status of the plant regulates citrulline. Taken together, these data provide further insights into the metabolic and molecular mechanisms underlying the amino acid metabolism under environmental stress and the significance of non-protein amino acid citrulline in plants.

mRNAs expression profiles of high glucose-induced memory in human umbilical vein endothelial cells

PURPOSE

A long-term "memory" of hyperglycemic stress, even when glycemia is normalized, has been previously reported in endothelial cells. However, the molecular mechanism of "metabolic memory" (MM) remains unknown. In this report, we sought to screen at the whole transcriptome level the genes that participate in MM.

METHODS

In the present research, RNA sequencing was used to determine the protein-coding mRNA expression profiles of human umbilical vein endothelial cells (HUVECs) under normal-glucose concentration (LG), high-glucose concentration (HG), and MM. A series of bioinformatic analyses was performed. HG-induced MM-involved up-regulated genes (up-HGMMGs) and HG-induced MM-involved down-regulated genes (down-HGMMGs) were identified. Afterward, based on up-HGMMGs and down-HGMMGs, the biological functions and signaling pathways were analyzed using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). In addition, several of the identified genes were validated by RT-qPCR.

RESULTS

A total of 726 HGMMGs were identified, including 210 down- and 516 up-HGMMGs, which were enriched in the cell cycle (hsa04110), oocyte meiosis (hsa04114), p53 signaling pathway (hsa04115), and oxidative phosphorylation (hsa00190), among others. The protein-protein-interaction (PPI) network consisted of 462 nodes and 2656 connections, and four main modules were identified by MCODE. The cell cycle (hsa04110), oocyte meiosis (hsa04114), p53 signaling pathway (hsa04115), and oxidative phosphorylation (hsa00190), among others, could be potential therapeutic targets of HG-induced MM in endothelial cells. The real-time PCR results validated the RNA-seq data.

CONCLUSION

This study identified crucial mRNAs related to MM-persistent injury in endothelial cells even after switching the cells from high- glucose to normal glucose levels. Further research focusing on these mRNA may unravel new ways to modify MM in diabetes.