Transcriptomic and Metabolomic Analysis of Seedling-Stage Soybean Responses to PEG-Simulated Drought Stress

Molecular mechanisms regulating glucose metabolism in quinoa (Chenopodium quinoa Willd.) seeds under drought stress

BACKGROUND

Abiotic stress seriously affects the growth and yield of crops. It is necessary to search and utilize novel abiotic stress resistant genes for 2.0 breeding programme in quinoa. In this study, the impact of drought stress on glucose metabolism were investigated through transcriptomic and metabolomic analyses in quinoa seeds. Candidate drought tolerance genes on glucose metabolism pathway were verified by qRT-PCR combined with yeast expression system.

RESULTS

From 70 quinoa germplasms, drought tolerant material M059 and drought sensitive material M024 were selected by comprehensive evaluation of drought resistance. 7042 differentially expressed genes (DEGs) were indentified through transcriptomic analyses. Gene Ontology (GO) analysis revealed that these DEGs were closely related to carbohydrate metabolic process, phosphorus-containing groups, and intracellular membrane-bounded organelles. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis detected that DEGs were related to pathways involving carbohydrate metabolisms, glycolysis and gluconeogenesis. Twelve key differentially accumulated metabolites (DAMs), (D-galactose, UDP-glucose, succinate, inositol, D-galactose, D-fructose-6-phosphate, D-glucose-6-phosphate, D-glucose-1-phosphate, dihydroxyacetone phosphate, ribulose-5-phosphate, citric acid and L-malate), and ten key candidate DEGs (CqAGAL2, CqINV, CqFrK7, CqCELB, Cqbg1x, CqFBP, CqALDO, CqPGM, CqIDH3, and CqSDH) involved in drought response were identified. CqSDH, CqAGAL2, and Cqβ-GAL13 were candidate genes that have been validated in both transcriptomics and yeast expression screen system.

CONCLUSION

These findings provide a foundation for elucidating the molecular regulatory mechanisms governing glucose metabolism in quinoa seeds under drought stress, providing insights for future research exploring responses to drought stress in quinoa.

Joint GWAS and WGCNA Identify Genes Regulating the Isoflavone Content in Soybean Seeds

Isoflavone is a secondary metabolite of the soybean phenylpropyl biosynthesis pathway with physiological activity and is beneficial to human health. In this study, the isoflavone content of 205 soybean germplasm resources from 3 locations in 2020 showed wide phenotypic variation. A joint genome-wide association study (GWAS) and weighted gene coexpression network analysis (WGCNA) identified 33 single-nucleotide polymorphisms and 11 key genes associated with soybean isoflavone content. Gene ontology enrichment analysis, gene coexpression, and haplotype analysis revealed natural variations in the Glyma.12G109800 (GmOMT7) gene and promoter region, with Hap1 being the elite haplotype. Transient overexpression and knockout of GmOMT7 increased and decreased the isoflavone content, respectively, in hairy roots. The combination of GWAS and WGCNA effectively revealed the genetic basis of soybean isoflavone and identified potential genes affecting isoflavone synthesis and accumulation in soybean, providing a valuable basis for the functional study of soybean isoflavone.

Cataloging the Genetic Response: Unveiling Drought-Responsive Gene Expression in Oil Tea Camellia (Camellia oleifera Abel.) through Transcriptomics

Drought stress is a critical environmental factor that significantly impacts plant growth and productivity. However, the transcriptome analysis of differentially expressed genes in response to drought stress in Camellia oleifera Abel. is still unclear. This study analyzed the transcriptome sequencing data of C. oleifera under drought treatments. A total of 20,674 differentially expressed genes (DEGs) were identified under drought stress, with the number of DEGs increasing with the duration of drought. Specifically, 11,793 and 18,046 DEGs were detected after 8 and 15 days of drought treatment, respectively, including numerous upregulated and downregulated genes. Gene Ontology (GO) enrichment analysis showed that the DEGs were primarily involved in various biological processes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that carbon metabolism, glyoxylate and dicarboxylate metabolism, proteasome, glycine, serine, and threonine metabolism were the main affected pathways. Among the DEGs, 376 protein kinases, 42 proteases, 168 transcription factor (TF) genes, and 152 other potential functional genes were identified, which may play significant roles in the drought response of C. oleifera. The expression of relevant functional genes was further validated using quantitative real-time PCR (qRT-PCR). These findings contribute to the comprehension of drought tolerance mechanisms in C. oleifera and bolster the identification of drought-resistant genes for molecular breeding purposes.

GmANKTM21 Positively Regulates Drought Tolerance and Enhanced Stomatal Response through the MAPK Signaling Pathway in Soybean

Drought stress is one of the significant abiotic stresses that limit soybean (Glycine max [L.] Merr.) growth and production. Ankyrin repeat (ANK) proteins, being highly conserved, occupy a pivotal role in diverse biological processes. ANK genes were classified into nine subfamilies according to conserved domains in the soybean genome. However, the function of ANK-TM subfamily proteins (Ankyrin repeat proteins with a transmembrane domain) in the abiotic-stress response to soybean remains poorly understood. In this study, we first demonstrated the subcellular localization of GmANKTM21 in the cell membrane and nucleus. Drought stress-induced mRNA levels of GmANKTM21, which encodes proteins belonging to the ANK-TM subfamily, Transgenic 35S:GmANKTM21 soybean improved drought tolerance at the germination and seedling stages, with higher stomatal closure in soybean, lower water loss, lower malondialdehyde (MDA) content, and less reactive oxygen species (ROS) production compared with the wild-type soybean (Dongnong50). RNA-sequencing (RNA-seq) and RT-qPCR analysis of differentially expressed transcripts in overexpression of GmANKTM21 further identified potential downstream genes, including GmSPK2, GmSPK4, and GmCYP707A1, which showed higher expression in transgenic soybean, than those in wild-type soybean and KEGG enrichment analysis showed that MAPK signaling pathways were mostly enriched in GmANKTM21 overexpressing soybean plants under drought stress conditions. Therefore, we demonstrate that GmANKTM21 plays an important role in tolerance to drought stress in soybeans.

Multi-Omics Analysis of a Chromosome Segment Substitution Line Reveals a New Regulation Network for Soybean Seed Storage Profile

Soybean, a major source of oil and protein, has seen an annual increase in consumption when used in soybean-derived products and the broadening of its cultivation range. The demand for soybean necessitates a better understanding of the regulatory networks driving storage protein accumulation and oil biosynthesis to broaden its positive impact on human health. In this study, we selected a chromosome segment substitution line (CSSL) with high protein and low oil contents to investigate the underlying effect of donor introgression on seed storage through multi-omics analysis. In total, 1479 differentially expressed genes (DEGs), 82 differentially expressed proteins (DEPs), and 34 differentially expressed metabolites (DEMs) were identified in the CSSL compared to the recurrent parent. Based on Gene Ontology (GO) term analysis and the Kyoto Encyclopedia of Genes and Genomes enrichment (KEGG), integrated analysis indicated that 31 DEGs, 24 DEPs, and 13 DEMs were related to seed storage functionality. Integrated analysis further showed a significant decrease in the contents of the seed storage lipids LysoPG 16:0 and LysoPC 18:4 as well as an increase in the contents of organic acids such as L-malic acid. Taken together, these results offer new insights into the molecular mechanisms of seed storage and provide guidance for the molecular breeding of new favorable soybean varieties.

Biochemical characterization and metabolic reprogramming of amino acids in Soybean roots under drought stress

Amino acids play important roles in stress resistance, plant growth, development, and quality, with roots serving as the primary organs for drought response. We conducted biochemical and multi-omics analyses to investigate the metabolic processes of root amino acids in drought-resistant (HN44) and drought-sensitive (HN65) soybean (Glycine max) varieties. Our analysis revealed an increase in total amino acid content in both varieties, with phenylalanine, proline, and methionine accumulating in both. Additionally, several amino acids exhibited significant decreases in HN65 but slight increases in HN44. Multi-omics association analysis identified 13 amino acid-related pathways. We thoroughly examined the changes in genes and metabolites involved in various amino acid metabolism/synthesis and determined core genes and metabolites through correlation networks. The phenylalanine, tyrosine, and tryptophan metabolic pathways and proline, glutamic acid and sulfur-containing amino acid pathways were particularly important for drought resistance. Some candidate genes, such as ProDH and P4HA family genes, and metabolites, such as O-acetyl-L-serine, directly affected up- and downstream metabolism to induce drought resistance. This study provided a basis for soybean drought resistance breeding.

Current views of drought research: experimental methods, adaptation mechanisms and regulatory strategies

Drought stress is one of the most important abiotic stresses which causes many yield losses every year. This paper presents a comprehensive review of recent advances in international drought research. First, the main types of drought stress and the commonly used drought stress methods in the current experiment were introduced, and the advantages and disadvantages of each method were evaluated. Second, the response of plants to drought stress was reviewed from the aspects of morphology, physiology, biochemistry and molecular progression. Then, the potential methods to improve drought resistance and recent emerging technologies were introduced. Finally, the current research dilemma and future development direction were summarized. In summary, this review provides insights into drought stress research from different perspectives and provides a theoretical reference for scholars engaged in and about to engage in drought research.

Molecular mechanism of drought resistance in soybean roots revealed using physiological and multi-omics analyses

Soybeans are one of the most cultivated crops worldwide and drought can seriously affect their growth and development. Many studies have elucidated the mechanisms through which soybean leaves respond to drought; however, little is known about these mechanisms in roots. We used two soybean varieties with different drought tolerances to study the morphological, physiological, and molecular response mechanisms of the root system to drought stress in seedlings. We found that drought stress led to a significant decrease in the root traits and an increase in antioxidant enzyme activity in the two varieties. Drought-resistant varieties accumulate large amounts of flavonoids and phenolic acids at the metabolic level, which causes variations in drought resistance. Additionally, differences in gene expression and drought-resistance pathways between the two varieties were clarified using transcriptome analysis. Through a multi-omics joint analysis, phenylpropanoid and isoflavonoid biosynthesis were identified as the core drought resistance pathways in soybean roots. Candidate genes and marker metabolites affecting drought resistance were identified. The phenylpropanoid pathway confers drought tolerance to roots by maintaining a high level of POD activity and mediates the biosynthesis of various secondary drought-resistant metabolites to resist drought stress. This study provides useful data for investigating plant root drought responses and offers theoretical support for plant breeding for drought resistance.

Comparative Analysis of Transcriptomics and Metabolomics Reveals Defense Mechanisms in Melon Cultivars against Pseudoperonospora cubensis Infection

Melon (Cucumis melo L.) represents an agriculturally significant horticultural crop that is widely grown for its flavorful fruits. Downy mildew (DM), a pervasive foliar disease, poses a significant threat to global melon production. Although several quantitative trait loci related to DM resistance have been identified, the comprehensive genetic underpinnings of this resistance remain largely uncharted. In this study, we utilized integrative transcriptomics and metabolomics approaches to identify potential resistance-associated genes and delineate the strategies involved in the defense against DM in two melon cultivars: the resistant 'PI442177' ('K10-1') and the susceptible 'Huangdanzi' ('K10-9'), post-P. cubensis infection. Even in the absence of the pathogen, there were distinctive differentially expressed genes (DEGs) between 'K10-1' and 'K10-9'. When P. cubensis was infected, certain genes, including flavin-containing monooxygenase (FMO), receptor-like protein kinase FERONIA (FER), and the HD-ZIP transcription factor member, AtHB7, displayed pronounced expression differences between the cultivars. Notably, our data suggest that following P. cubensis infection, both cultivars suppressed flavonoid biosynthesis via the down-regulation of associated genes whilst concurrently promoting lignin production. The complex interplay of transcriptomic and metabolic responses elucidated by this study provides foundational insights into melon's defense mechanisms against DM. The robust resilience of 'K10-1' to DM is attributed to the synergistic interaction of its inherent transcriptomic and metabolic reactions.

Physiological responses and transcriptome analysis of soybean under gradual water deficit

Soybean is an important food and oil crop widely cultivated globally. However, water deficit can seriously affect the yield and quality of soybeans. In order to ensure the stability and increase of soybean yield and improve agricultural water use efficiency (WUE), research on improving drought tolerance and the efficiency of water utilization of soybeans under drought stress has become particularly important. This study utilized the drought-tolerant variety Heinong 44 (HN44) and the drought-sensitive variety Suinong 14 (SN14) to analyze physiological responses and transcriptome changes during the gradual water deficit at the early seed-filling stage. The results indicated that under drought conditions, HN44 had smaller stomata, higher stomatal density, and lower stomatal conductance (Gs) and transpiration rate as compared to SN14. Additionally, HN44 had a higher abscisic acid (ABA) content and faster changes in stomatal morphology and Gs to maintain a dynamic balance between net photosynthetic rate (Pn) and Gs. Additionally, drought-tolerant variety HN44 had high instantaneous WUE under water deficit. Further, HN44 retained a high level of superoxide dismutase (SOD) activity and proline content, mitigating malondialdehyde (MDA) accumulation and drought-induced damage. Comprehensive analysis of transcriptome data revealed that HN44 had fewer differentially expressed genes (DEGs) under light drought stress, reacting insensitivity to water deficit. At the initial stage of drought stress, both varieties had a large number of upregulated DEGs to cope with the drought stress. Under severe drought stress, HN44 had fewer downregulated genes enriched in the photosynthesis pathway than SN14, while it had more upregulated genes enriched in the ABA-mediated signaling and glutathione metabolism pathways than SN14. During gradual water deficit, HN44 demonstrated better drought-tolerant physiological characteristics and water use efficiency than SN14 through key DEGs such as GmbZIP4, LOC100810474, and LOC100819313 in the major pathways. Key transcription factors were screened and identified, providing further clarity on the molecular regulatory pathways responsible for the physiological differences in drought tolerance among these varieties. This study deepened the understanding of the drought resistance mechanisms in soybeans, providing valuable references for drought-resistant soybean breeding.

Subcellular Proteomics to Elucidate Soybean Response to Abiotic Stress

Climate change jeopardizes soybean production by declining seed yield and quality. In this review, the morphophysiological alterations of soybean in response to abiotic stress are summarized, followed by illustrations of cellular metabolisms and regulatory mechanisms to organellar stress based on subcellular proteomics. This highlights the communications associated with reactive oxygen species scavenging, molecular chaperones, and phytohormone signals among subcellular compartments. Given the complexity of climate change and the limitations of plants in coping with multiple abiotic stresses, a generic response to environmental constraints is proposed between calcium and abscisic acid signals in subcellular organelles. This review summarizes the findings of subcellular proteomics in stressed soybean and discusses the future prospects of subcellular proteomics for promoting the improvement of climate-tolerant crops.

Multi-Omics Pipeline and Omics-Integration Approach to Decipher Plant's Abiotic Stress Tolerance Responses

The present day's ongoing global warming and climate change adversely affect plants through imposing environmental (abiotic) stresses and disease pressure. The major abiotic factors such as drought, heat, cold, salinity, etc., hamper a plant's innate growth and development, resulting in reduced yield and quality, with the possibility of undesired traits. In the 21st century, the advent of high-throughput sequencing tools, state-of-the-art biotechnological techniques and bioinformatic analyzing pipelines led to the easy characterization of plant traits for abiotic stress response and tolerance mechanisms by applying the 'omics' toolbox. Panomics pipeline including genomics, transcriptomics, proteomics, metabolomics, epigenomics, proteogenomics, interactomics, ionomics, phenomics, etc., have become very handy nowadays. This is important to produce climate-smart future crops with a proper understanding of the molecular mechanisms of abiotic stress responses by the plant's genes, transcripts, proteins, epigenome, cellular metabolic circuits and resultant phenotype. Instead of mono-omics, two or more (hence 'multi-omics') integrated-omics approaches can decipher the plant's abiotic stress tolerance response very well. Multi-omics-characterized plants can be used as potent genetic resources to incorporate into the future breeding program. For the practical utility of crop improvement, multi-omics approaches for particular abiotic stress tolerance can be combined with genome-assisted breeding (GAB) by being pyramided with improved crop yield, food quality and associated agronomic traits and can open a new era of omics-assisted breeding. Thus, multi-omics pipelines together are able to decipher molecular processes, biomarkers, targets for genetic engineering, regulatory networks and precision agriculture solutions for a crop's variable abiotic stress tolerance to ensure food security under changing environmental circumstances.

Mechanism of Mepiquat Chloride Regulating Soybean Response to Drought Stress Revealed by Proteomics

Soybeans are the main sources of oil and protein for most of the global population. As the population grows, so does the demand for soybeans. However, drought is a major factor that limits soybean production. Regulating soybean response to drought stress using mepiquat chloride (MC) is a feasible method; however, its mechanism is still unclear. This study used PEG-6000 to simulate drought stress and quantitative proteomic techniques to reveal changes in Heinong44 (HN44) and Heinong65 (HN65) subjected to drought following the application of 100 mg/L of MC. The results showed that SOD in HN44 did not change significantly but decreased by 22.61% in HN65 after MC pretreatment, and MDA content decreased by 22.75% and 21.54% in HN44 and HN65, respectively. Furthermore, MC improved the GSH-ASA cycle and simultaneously promoted the Calvin cycle process to enable the plant to maintain a certain carbon assimilation rate under osmotic stress. In addition, MC upregulated some proteins during gluconeogenesis and starch metabolism and increased soluble sugar content by 8.41% in HN44. MC also reduced ribosomal protein abundance, affecting translation and amino acid metabolism. In summary, MC improved GSH-ASA cycle and Calvin cycle under stress to alleviate oxidative damage and maintain crop growth. Our study is the first to report the mechanism of MC regulation in soybean under osmotic stress, providing new insights for the rational application of MC in soybean.

New Insights Into Short-term Water Stress Tolerance Through Transcriptomic and Metabolomic Analyses on Pepper Roots

In the current climate change scenario, water stress is a serious threat to limit crop growth and yields. It is necessary to develop tolerant plants that cope with water stress and, for this purpose, tolerance mechanisms should be studied. NIBER® is a proven water stress- and salt-tolerant pepper hybrid rootstock (Gisbert-Mullor et al., 2020; López-Serrano et al., 2020), but tolerance mechanisms remain unclear. In this experiment, NIBER® and A10 (a sensitive pepper accession (Penella et al., 2014)) response to short-term water stress at 5 h and 24 h was studied in terms of gene expression and metabolites content in roots. GO terms and gene expression analyses evidenced constitutive differences in the transcriptomic profile of NIBER® and A10, associated with detoxification systems of reactive oxygen species (ROS). Upon water stress, transcription factors like DREBs and MYC are upregulated and the levels of auxins, abscisic acid and jasmonic acid are increased in NIBER®. NIBER® tolerance mechanisms involve an increase in osmoprotectant sugars (i.e., trehalose, raffinose) and in antioxidants (spermidine), but lower contents of oxidized glutathione compared to A10, which indicates less oxidative damage. Moreover, the gene expression for aquaporins and chaperones is enhanced. These results show the main NIBER® strategies to overcome water stress.

Regulation of soybean drought response by mepiquat chloride pretreatment

Introduction

Soybean is the world's most important cultivated crop, and drought can affect their growth and, eventually, yields. Foliar application of mepiquat chloride (MC) can potentially alleviate the damage caused by drought stress in plants; however, the mechanism of MC regulation of soybean drought response has not been studied.

Methods

This study investigated the mechanism of soybean drought response regulation by mepiquat chloride in two varieties of soybean, sensitive Heinong 65 (HN65) and drought-tolerant Heinong44 (HN44), under three treatment scenarios, normal, drought stress, and drought stress + MC conditions.

Results and discussion

MC promoted dry matter accumulation under drought stress, reduced plant height, decreased antioxidant enzyme activity, and significantly decreased malondialdehyde content. The light capture processes, photosystems I and II, were inhibited; however, accumulation and upregulation of several amino acids and flavonoids by MC was observed. Multi-omics joint analysis indicated 2-oxocarboxylic acid metabolism and isoflavone biosynthetic pathways to be the core pathways by which MC regulated soybean drought response. Candidate genes such as LOC100816177, SOMT-2, LOC100784120, LOC100797504, LOC100794610, and LOC100819853 were identified to be crucial for the drought resistance of soybeans. Finally, a model was constructed to systematically describe the regulatory mechanism of MC application in soybean under drought stress. This study fills the research gap of MC in the field of soybean resistance.

Identification of hub genes regulating isoflavone accumulation in soybean seeds via GWAS and WGCNA approaches

INTRODUCTION

Isoflavones are the secondary metabolites synthesized by the phenylpropanoid biosynthesis pathway in soybean that benefits human and plant health.

METHODS

In this study, we have profiled seed isoflavone content by HPLC in 1551 soybean accessions grown in Beijing and Hainan for two consecutive years (2017 and 2018) and in Anhui for one year (2017).

RESULTS

A broad range of phenotypic variations was observed for individual and total isoflavone (TIF) content. The TIF content ranged from 677.25 to 5823.29 µg g^-1 in the soybean natural population. Using a genome-wide association study (GWAS) based on 6,149,599 single nucleotide polymorphisms (SNPs), we identified 11,704 SNPs significantly associated with isoflavone contents; 75% of them were located within previously reported QTL regions for isoflavone. Two significant regions on chromosomes 5 and 11 were associated with TIF and malonylglycitin across more than 3 environments. Furthermore, the WGCNA identified eight key modules: black, blue, brown, green, magenta, pink, purple, and turquoise. Of the eight co-expressed modules, brown (r = 0.68***), magenta (r = 0.64***), and green (r = 0.51**) showed a significant positive association with TIF, as well as with individual isoflavone contents. By combining the gene significance, functional annotation, and enrichment analysis information, four hub genes Glyma.11G108100, Glyma.11G107100, Glyma.11G106900, and Glyma.11G109100 encoding, basic-leucine zipper (bZIP) transcription factor, MYB4 transcription factor, early responsive to dehydration, and PLATZ transcription factor respectively were identified in brown and green modules. The allelic variation in Glyma.11G108100 significantly influenced individual and TIF accumulation.

DISCUSSION

The present study demonstrated that the GWAS approach, combined with WGCNA, could efficiently identify isoflavone candidate genes in the natural soybean population.

Wild soybean salt tolerance metabolic model: Assessment of storage protein mobilization in cotyledons and C/N balance in the hypocotyl/root axis

Salt stress has become one of the main factors limiting crop yield in recent years. The post-germinative growth is most sensitive to salt stress in soybean. In this study, cultivated and wild soybeans were used for an integrated metabonomics and transcriptomics analysis to determine whether wild soybean can resist salt stress by maintaining the mobilization of stored substances in cotyledons and the balance of carbon and nitrogen in the hypocotyl/root axis (HRA). Compared with wild soybean, the growth of cultivated soybean was significantly inhibited during the post-germinative growth period under salt stress. Integrating analysis found that the breakdown products of proteins, such as glutamate, glutamic acid, aspartic acid, and asparagine, increased significantly in wild soybean cotyledons. Asparagine synthase and fumarate hydratase genes and genes encoding HSP20 family proteins were specifically upregulated. In wild soybean HRA, levels of glutamic acid, aspartic acid, asparagine, citric acid, and succinic acid increased significantly, and the glutamate decarboxylase gene and the gene encoding carbonic anhydrase in nitrogen metabolism were significantly upregulated. The metabolic model indicated that wild soybean enhanced the decomposition of stored proteins and the transport of amino acids to the HRA in cotyledons and the GABA shunt to maintain carbon and nitrogen balance in the HRA to resist salt stress. This study provided a theoretical basis for cultivating salt-tolerant soybean varieties and opened opportunities for the development of sustainable agricultural practices.

Multi-omics revolution to promote plant breeding efficiency

Crop production is the primary goal of agricultural activities, which is always taken into consideration. However, global agricultural systems are coming under increasing pressure from the rising food demand of the rapidly growing world population and changing climate. To address these issues, improving high-yield and climate-resilient related-traits in crop breeding is an effective strategy. In recent years, advances in omics techniques, including genomics, transcriptomics, proteomics, and metabolomics, paved the way for accelerating plant/crop breeding to cope with the changing climate and enhance food production. Optimized omics and phenotypic plasticity platform integration, exploited by evolving machine learning algorithms will aid in the development of biological interpretations for complex crop traits. The precise and progressive assembly of desire alleles using precise genome editing approaches and enhanced breeding strategies would enable future crops to excel in combating the changing climates. Furthermore, plant breeding and genetic engineering ensures an exclusive approach to developing nutrient sufficient and climate-resilient crops, the productivity of which can sustainably and adequately meet the world's food, nutrition, and energy needs. This review provides an overview of how the integration of omics approaches could be exploited to select crop varieties with desired traits.

Transcriptomic and Metabolomic Analyses Reveal That Fullerol Improves Drought Tolerance in Brassica napus L

Carbon nanoparticles have potential threats to plant growth and stress tolerance. The polyhydroxy fullerene-fullerol (one of the carbon nanoparticles) could increase biomass accumulation in several plants subjected to drought; however, the underlying molecular and metabolic mechanisms governed by fullerol in improving drought tolerance in Brassica napus remain unclear. In the present study, exogenous fullerol was applied to the leaves of B. napus seedlings under drought conditions. The results of transcriptomic and metabolomic analyses revealed changes in the molecular and metabolic profiles of B. napus. The differentially expressed genes and the differentially accumulated metabolites, induced by drought or fullerol treatment, were mainly enriched in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to carbohydrate metabolism (e.g., "carbon metabolism" and "galactose metabolism"), amino acid metabolism (e.g., "biosynthesis of amino acids" and "arginine and proline metabolism"), and secondary metabolite metabolism (e.g., "biosynthesis of secondary metabolites"). For carbohydrate metabolism, the accumulation of oligosaccharides (e.g., sucrose) was decreased, whereas that of monosaccharides (e.g., mannose and myo-inositol) was increased by drought. With regard to amino acid metabolism, under drought stress, the accumulation of amino acids such as phenylalanine and tryptophan decreased, whereas that of glutamate and proline increased. Further, for secondary metabolite metabolism, B. napus subjected to soil drying showed a reduction in phenolics and flavonoids, such as hyperoside and trans-3-coumaric acid. However, the accumulation of carbohydrates was almost unchanged in fullerol-treated B. napus subjected to drought. When exposed to water shortage, the accumulation of amino acids, such as proline, was decreased upon fullerol treatment. However, that of phenolics and flavonoids, such as luteolin and trans-3-coumaric acid, was enhanced. Our findings suggest that fullerol can alleviate the inhibitory effects of drought on phenolics and flavonoids to enhance drought tolerance in B. napus.

Molecular Characterization and Drought Resistance of GmNAC3 Transcription Factor in Glycine max (L.) Merr

Soybean transcription factor GmNAC plays important roles in plant resistance to environmental stresses. In this study, GmNAC3 was cloned in the drought tolerant soybean variety “Jiyu47”, with the molecular properties of GmNAC3 characterized to establish its candidacy as a NAC transcription factor. The yeast self-activation experiments revealed the transcriptional activation activity of GmNAC3, which was localized in the nucleus by the subcellular localization analysis. The highest expression of GmNAC3 was detected in roots in the podding stage of soybean, and in roots of soybean seedlings treated with 20% PEG6000 for 12 h, which was 16 times higher compared with the control. In the transgenic soybean hairy roots obtained by the Agrobacterium-mediated method treated with 20% PEG6000 for 12 h, the activities of superoxide dismutase, peroxidase, and catalase and the content of proline were increased, the malondialdehyde content was decreased, and the expressions of stress resistance-related genes (i.e., APX2, LEA14, 6PGDH, and P5CS) were up-regulated. These expression patterns were confirmed by transgenic Arabidopsis thaliana with the overexpression of GmNAC3. This study provided strong scientific evidence to support further investigation of the regulatory function of GmNAC3 in plant drought resistance and the molecular mechanisms regulating the plant response to environmental stresses.

Screening and identification of drought tolerance of spring soybean at seedling stage under climate change

Drought is one of the major abiotic stress factors limiting soybean growth and yield, and it frequently occur globally. Therefore, exploring resistant varieties from soybean germplasm is important under climate change. To screen drought resistant spring soybean varieties at seedling stage, pot experiment was used to detect the Survival percentage after drought stress of 60 soybean varieties at seedling stage, twice drought rehydration treatments on seedlings, to evaluate the drought tolerance of spring soybean. The results showed that at the seedling stage, seven varieties were considered drought tolerant, 17 varieties were considered drought sensitive, and 36 varieties were considered to be moderately drought tolerant. Based on this experiment, number 44 (heinong37), 48 (heinong44), 49 (heinong45), 52 (heinong48) is considered the best drought resistant, and number 3 (dongnong48), 4 (dongnong52), 27 (suinong25), 60 (heinong65) is the most sensitive. These varieties provide a reference for further study on drought tolerance and stress resistance gene screening of soybean at the molecular level. The selected soybean varieties can be planted in areas with suitable climates and frequent drought to meet the local soybean demand. In other regions, although cannot be directly grown, they can still be used as parents of selected varieties or as materials for gene screening and extraction, to assist crop breeding at the molecular level in response to increasingly severe drought stress problems under the current climate trends.

Transcriptome Level Analysis of Genes of Exogenous Ethylene Applied under Phosphorus Stress in Chinese Fir

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is a widely grown gymnosperm in China. Phosphorus (P) is an indispensable nutrient for the growth of Chinese fir. Inorganic phosphate (Pi) deficiency exists in soils of many Chinese fir planting area regions, and the trees themselves have limited efficiency in utilizing P from the soil. Ethylene is important in regulation responses to nutrient deficiencies. However, little is known about how ethylene signals participate in Pi stress in Chinese fir. A total of six different treatments were performed to reveal the transcript levels of Chinese fir under Pi, ethephon (an ethylene-releasing compound), and CoCl₂ (cobalt chloride, an ethylene biosynthesis inhibitor) treatments. We assembled a full-length reference transcriptome containing 22,243 unigenes as a reference for UMI RNA-seq (Digital RNA-seq). There were 586 Differentially Expressed Genes (DEGs) in the Pi starvation (NP) group, while DEGs from additional ethephon or CoCl₂ in NP were 708 and 292, respectively. Among the DEGs in each treatment, there were 83 TFs in these treatment groups. MYB (v-myb avian myeloblastosis viral oncogene homolog) family was the most abundant transcription factors (TFs). Three ERF (Ethylene response factor) family genes were identified when only ethylene content was imposed as a variable. Enrichment analysis indicated that the ascorbate and aldarate metabolism pathway plays a key role in resistance to Pi deficiency. This study provides insights for further elucidating the regulatory mechanism of Pi deficiency in Chinese fir.