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Rapeseed ( Brassica napus L.) is extremely sensitive to excessive NH 4 + toxicity. There remains incomplete knowledge of the causal factors behind the growth suppression in NH 4 + -nourished plants, with limited studies conducted specifically on field crop plants. In this study, we found that NH 4 + toxicity significantly increased salicylic acid (SA) accumulation by accelerating the conversion of SA precursors. Moreover, exogenous SA application significantly aggravated NH 4 + toxicity symptoms in the rapeseed shoots. Genome-wide differential transcriptomic analysis showed that NH 4 + toxicity increased the expression of genes involved in the biosynthesis, transport, signaling transduction, and conversion of SA. SA treatment significantly increased shoot NH 4 + concentrations by reducing the activities of glutamine synthase and glutamate synthase in NH 4 + -treated rapeseed plants. The application of an SA biosynthesis inhibitor, ABT, alleviated NH 4 + toxicity symptoms. Furthermore, SA induced putrescine (Put) accumulation, resulting in an elevated ratio of Put to [spermidine (Spd) + spermine (Spm)] in the NH 4 + -treated plants, while the opposite was true for ABT. The application of exogenous Put and its biosynthesis inhibitor DFMA induced opposite effects on NH 4 + toxicity in rapeseed shoots. These results indicated that the increased endogenous SA contributed noticeably to the toxicity caused by the sole NH 4 + -N supply in rapeseed shoots. This study provided fresh perspectives on the mechanism underlying excessive NH 4 + -induced toxicity and the corresponding alleviating strategies in plants.

Key Message: Integrated phenomics, ionomics, genomics, transcriptomics, and functional analyses present novel insights into the role of pectin demethylation-mediated cell wall Na + retention in positively regulating salt tolerance in oilseed rape. Genetic variations in salt stress tolerance identified in rapeseed genotypes highlight the complicated regulatory mechanisms. Westar is ubiquitously used as a transgenic receptor cultivar, while ZS11 is widely grown as a high-production and good-quality cultivar. In this study, Westar was found to outperform ZS11 under salt stress. Through cell component isolation, non-invasive micro-test, X-ray energy spectrum analysis, and ionomic profile characterization, pectin demethylation-mediated cell wall Na + retention was proposed to be a major regulator responsible for differential salt tolerance between Westar and ZS11. Integrated analyses of genome-wide DNA variations, differential expression profiling, and gene co-expression networks identified BnaC9.PME47, encoding a pectin methylesterase, as a positive regulator conferring salt tolerance in rapeseed. BnaC9.PME47, located in two reported QTL regions for salt tolerance, was strongly induced by salt stress and localized on the cell wall. Natural variation of the promoter regions conferred higher expression of BnaC9.PME47 in Westar than in several salt-sensitive rapeseed genotypes. Loss of function of AtPME47 resulted in the hypersensitivity of Arabidopsis plants to salt stress. The integrated multiomics analyses revealed novel insights into pectin demethylation-mediated cell wall Na + retention in regulating differential salt tolerance in allotetraploid rapeseed genotypes. Furthermore, these analyses have provided key information regarding the rapid dissection of quantitative trait genes responsible for nutrient stress tolerance in plant species with complex genomes., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Rapeseed (Brassica napus L.) is susceptible to nutrient stresses during growth and development; however, the CPA (cation proton antiporter) family genes have not been identified in B. napus and their biological functions remain unclear. This study was aimed to identify the molecular characteristics of rapeseed CPAs and their transcriptional responses to multiple nutrient stresses. Through bioinformatics analysis, 117 BnaCPAs, consisting of three subfamilies: Na + /H + antiporter (NHX), K + efflux antiporter (KEA), and cation/H + antiporter (CHX), were identified in the rapeseed genome. Transcriptomic profiling showed that BnaCPAs, particularly BnaNHXs, were transcriptionally responsive to diverse nutrient stresses, including Cd toxicity, K starvation, salt stress, NH 4 + toxicity, and low Pi. We found that the salt tolerance of the transgenic rapeseed lines overexpressing BnaA05.NHX2 was significantly higher than that of wild type. Subcellular localization showed that BnaA05.NHX2 was localized on the tonoplast, and TEM combined with X-ray energy spectrum analysis revealed that the vacuolar Na + concentrations of the BnaA05.NHX2-overexpressing rapeseed plants were significantly higher than those of wild type. The findings of this study will provide insights into the complexity of the BnaCPA family and a valuable resource to explore the in-depth functions of CPAs in B. napus., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Variations in the resistance to potassium (K) deficiency among rapeseed genotypes emphasize complicated regulatory mechanisms. In this study, a low-K-sensitivity accession (L49) responded to K deficiency with smaller biomasses, severe leaf chlorosis, weaker photosynthesis ability, and deformed stomata morphology compared to a low-K resistant accession (H280). H280 accumulated more K + than L49 under low K. Whole-genome resequencing (WGS) revealed a total of 5,538,622 single nucleotide polymorphisms (SNPs) and 859,184 insertions/deletions (InDels) between H280 and L49. RNA-seq identified more differentially expressed K + transporter genes with higher expression in H280 than in L49 under K deficiency. Based on the K + profiles, differential expression profiling, weighted gene coexpression network analysis, and WGS data between H280 and L49, BnaC4.AKT1 was proposed to be mainly responsible for root K absorption-mediated low K resistance. BnaC4.AKT1 was expressed preferentially in the roots and localized on the plasma membrane. An SNP and an InDel found in the promoter region of BnaC4.AKT1 were proposed to be responsible for its differential expression between rapeseed genotypes. This study identified a gene resource for improving low-K resistance. It also facilitates an integrated knowledge of the differential physiological and transcriptional responses to K deficiency in rapeseed genotypes.

The GARP genes are plant-specific transcription factors (TFs) and play key roles in regulating plant development and abiotic stress resistance. However, few systematic analyses of GARPs have been reported in allotetraploid rapeseed ( Brassica napus L.) yet. In the present study, a total of 146 BnaGARP members were identified from the rapeseed genome based on the sequence signature. The BnaGARP TFs were divided into five subfamilies: ARR , GLK , NIGT1/HRS1/HHO , KAN , and PHL subfamilies, and the members within the same subfamilies shared similar exon-intron structures and conserved motif configuration. Analyses of the Ka/Ks ratios indicated that the GARP family principally underwent purifying selection. Several cis -acting regulatory elements, essential for plant growth and diverse biotic and abiotic stresses, were identified in the promoter regions of BnaGARPs . Further, 29 putative miRNAs were identified to be targeting BnaGARPs . Differential expression of BnaGARPs under low nitrate, ammonium toxicity, limited phosphate, deficient boron, salt stress, and cadmium toxicity conditions indicated their potential involvement in diverse nutrient stress responses. Notably, BnaA9.HHO1 and BnaA1.HHO5 were simultaneously transcriptionally responsive to these nutrient stresses in both hoots and roots, which indicated that BnaA9.HHO1 and BnaA1.HHO5 might play a core role in regulating rapeseed resistance to nutrient stresses. Therefore, this study would enrich our understanding of molecular characteristics of the rapeseed GARPs and will provide valuable candidate genes for further in-depth study of the GARP-mediated nutrient stress resistance in rapeseed.

Autophagy is a common physiological process in organisms, including higher plants. The ATG8 subfamily, the core member of the autophagy-related gene (ATG) family, plays a key role in plant growth and development and nutrient stress responses. However, the core ATG8 homologs and their roles in stress resistance remain elusive in allotetraploid rapeseed (AACC, Brassica napus L.). In this study, we identified 29 ATG8 subgroup members, consisting of three phylogenetic clades, based on the analysis of genomic annotation and conserved motifs. Differential transcriptional responses of BnaATG8s to salt stress, nitrogen limitation, and other nutrient stresses were investigated, and we identified BnaA8.ATG8F as the core ATG8 member through gene co-expression network analysis. Decreased BnaA8.ATG8F expression repressed the salt tolerance of transgenic rapeseed plants by significantly reducing the root Na + retention under salt stress. Moreover, downregulation of BnaA8.ATG8F increased nitrogen (N) limitation sensitivity of transgenic rapeseed plants through decreasing N uptake, translocation, and enhancing N remobilization under nitrogen starvation. In summary, we identified the core ATG8 homologs and characterized their physiological and molecular mechanisms underlying salt stress tolerance and nitrogen limitation adaptation. Our results may provide elite genetic resources for the genetic improvement of nutrient stress tolerance in rapeseed.

Plant roots acquire nitrogen predominantly as two inorganic forms, nitrate (NO3-) and ammonium (NH4+), to which plants respond differentially. Rapeseed (Brassica napus L.) is an important oil-crop species with very low nitrogen-use efficiency (NUE), the regulatory mechanism of which was elusive due to the vastness and complexity of the rapeseed genome. In this study, a comparative transcriptomic analysis was performed to investigate the differential signatures of nitrogen-starved rapeseed in responses to NO3- and NH4+ treatments and to identify the key genes regulating rapeseed NUE. The two nitrogen sources differentially affected the shoot and root transcriptome profiles, including those of genome-wide nitrogen transporter and transcription factor (TF)-related genes. Differential expression profiling showed that BnaA6.NRT2;1 and BnaA7.AMT1;3 might be the core transporters responsible for efficient NO3- and NH4+ uptake, respectively; the TF genes responsive to inorganic nitrogen, specifically responding to NO3-, and specifically responsive to NH4+ were also identified. The genes which were commonly and most significantly affected by both NO3- and NH4+ treatments were related to glutamine metabolism. Among the glutamine synthetase (GS) family genes, we found BnaA2.Gln1;4, significantly responsive to low-nitrogen conditions and showed higher transcription abundance and GS activity in the leaf veins, flower sepals, root cortex and stele, silique petiole and stem tissues. These characters were significantly different from those of AtGln1;4. The heterologous overexpression of BnaA2.Gln1;4 in Arabidopsis increased plant biomass, NUE, GS activity and total amino acid concentrations under both sufficient- and low-nitrogen conditions. Overall, this study provided novel information about the genes involved in the adaptation to different nitrogen regimes and identified some promising candidate genes for enhancing NUE in rapeseed., (© The Author(s) 2022. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: Oilseed rape (B. napus L.) has great potential for phytoremediation of cadmium (Cd)-polluted soils due to its large plant biomass production and strong metal accumulation. Soil properties and the presence of other soluble compounds or ions, cause a heterogeneous distribution of Cd., Results: The aim of our study was to reveal the differential responses of B. napus to different Cd abundances. Herein, we found that high Cd (50 μM) severely inhibited the growth of B. napus, which was not repressed by low Cd (0.50 μM) under hydroponic culture system. ICP-MS assays showed that the Cd 2+ concentrations in both shoots and roots under 50 μM Cd were over 10 times higher than those under 0.50 μM Cd. Under low Cd, the concentrations of only shoot Ca 2+ /Mn 2+ and root Mn 2+ were obviously changed (both reduced); under high Cd, the concentrations of most cations assayed were significantly altered in both shoots and roots except root Ca 2+ and Mg 2+ . High-throughput transcriptomic profiling revealed a total of 18,021 and 1408 differentially expressed genes under high Cd and low Cd conditions, respectively. The biological categories related to the biosynthesis of plant cell wall components and response to external stimulus were over-accumulated under low Cd, whereas the terms involving photosynthesis, nitrogen transport and response, and cellular metal ion homeostasis were highly enriched under high Cd. Differential expression of the transporters responsible for Cd uptake (NRAMPs), transport (IRTs and ZIPs), sequestration (HMAs, ABCs, and CAXs), and detoxification (MTPs, PCR, MTs, and PCSs), and some other essential nutrient transporters were investigated, and gene co-expression network analysis revealed the core members of these Cd transporters. Some Cd transporter genes, especially NRAMPs and IRTs, showed opposite responsive patterns between high Cd and low Cd conditions., Conclusions: Our findings would enrich our understanding of the interaction between essential nutrients and Cd, and might also provide suitable gene resources and important implications for the genetic improvement of plant Cd accumulation and resistance through molecular engineering of these core genes under varying Cd abundances in soils., (© 2021. The Author(s).)

Background: Nitrogen (N) is an essential macronutrient to maintain plant growth and development. Plants absorb nitrate-N or ammonium-N in the environment and undergo reduction reactions catalyzed by nitrate reductase (NR), nitrite reductase (NIR), glutamine synthetase (GS), and glutamine oxoglutarate aminotransferase (GOGAT) within plants., Methods and Results: A total of 42 N assimilation-related genes (NAG) members were identified in rapeseed. Darwin's evolutionary pressure analysis showed that rapeseed NAGs underwent purification selection. Cis-element analysis revealed differences in the transcriptional regulation of NAGs between Arabidopsis and rapeseed. Expression analyses revealed that NRs were expressed mainly in old leaves, NIRs were expressed mainly in old leaves and lower stem peels, while the expression situation between different subfamilies of GSs and GOGATs was more complicated., Conclusions: Differential expression of NAGs suggested that they might be involved in abiotic stresses. The above results greatly enriched our understanding of NAGs' molecular characteristics and provided central gene resources for NAGs-mediated NUE improvement in rapeseed., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

The large size and complexity of the allotetraploid rapeseed (Brassica napus) genome present huge challenges for understanding salinity resistance in this important crop. In this study, we identified two rapeseed genotypes with significantly different degrees of salinity resistance and examined the underlying mechanisms using an integrated analysis of phenomics, ionomics, genomics, and transcriptomics. Under salinity, a higher accumulation of osmoregulation substances and better root-system architecture was observed in the resistant genotype, H159, than in the sensitive one, L339. A lower shoot Na+ concentration and a higher root vacuolar Na+ concentration indicated lower root-to-shoot translocation and higher compartmentation in H159 than in L339. Whole-genome re-sequencing (WGRS) and transcriptome sequencing identified numerous DNA variants and differentially expressed genes involved in abiotic stress responses and ion transport. Combining ionomics with transcriptomics identified plasma membrane-localized BnaC2.HKT1;1 and tonoplast-localized BnaC5.NHX2 as the central factors regulating differential root xylem unloading and vacuolar sequestration of Na+ between the two genotypes. Identification of polymorphisms by WGRS and PCR revealed two polymorphic MYB-binding sites in the promoter regions that might determine the differential gene expression of BnaC2.HKT1;1 and BnaC5.NHX2. Our multiomics approach thus identified core transporters involved in Na+ translocation and compartmentation that regulate salinity resistance in rapeseed. Our results may provide elite gene resources for the improvement of salinity resistance in this crop, and our multiomics approach can be applied to other similar studies., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Background: B-box (BBX) genes play important roles in plant growth regulation and responses to abiotic stresses. The plant growth and yield production of allotetraploid rapeseed is usually hindered by diverse nutrient stresses. However, no systematic analysis of Brassicaceae BBXs and the roles of BBXs in the regulation of nutrient stress responses have not been identified and characterized previously., Results: In this study, a total of 536 BBXs were identified from nine brassicaceae species, including 32 AtBBXs, 66 BnaBBXs, 41 BoBBXs, 43 BrBBXs, 26 CrBBXs, 81 CsBBXs, 52 BnBBXs, 93 BjBBXs, and 102 BcBBXs. Syntenic analysis showed that great differences in the gene number of Brassicaceae BBXs might be caused by genome duplication. The BBXs were respectively divided into five subclasses according to their phylogenetic relationships and conserved domains, indicating their diversified functions. Promoter cis-element analysis showed that BBXs probably participated in diverse stress responses. Protein-protein interactions between BnaBBXs indicated their functions in flower induction. The expression profiles of BnaBBXs were investigated in rapeseed plants under boron deficiency, boron toxicity, nitrate limitation, phosphate shortage, potassium starvation, ammonium excess, cadmium toxicity, and salt stress conditions using RNA-seq data. The results showed that different BnaBBXs showed differential transcriptional responses to nutrient stresses, and some of them were simultaneously responsive to diverse nutrient stresses., Conclusions: Taken together, the findings investigated in this study provided rich resources for studying Brassicaceae BBX gene family and enriched potential clues in the genetic improvement of crop stress resistance.

Fatty acid desaturase-2 (FAD2) is a key enzyme in the production of polyunsaturated fatty acids in plants. RNAi technology can reduce the expression of FAD2 genes in Brassica napus seeds and acquire transgenic B. napus plants with a high oleic acid content, but the effect of seed-specific inhibition of FAD2 expression on B. napus seed metabolites is not clear. Here we use widely targeted metabolomics to investigate the metabolites of normal-oleic-acid rapeseed (OA) and high-oleic-acid rapeseed (HOA) seeds, resulting in a total of 726 metabolites being detected. Among them, 24 differential metabolites were significantly downregulated and 88 differential metabolites were significantly upregulated in HOA rapeseed. In further lipid profile experiments, more lipids in B. napus seeds were accurately quantified. The contents of glycolipids and phospholipids that contain C18:1 increased significantly and C18:2 decreased because FAD2 expression was inhibited. The changes in the expression of key genes in related pathways were also consistent with the changes in metabolites. The insertion site of the ihpRNA plant expression vector was reconfirmed through genomewide resequencing, and the transgenic event did not change the sequence of FAD2 genes. There was no significant difference in the germination rate and germination potential between OA and HOA rapeseed seeds because the seed-specific ihpRNA plant expression vector did not affect other stages of plant growth. This work provides a theoretical and practical guidance for subsequent molecular breeding of high OA B. napus .

Background: Salinity severely inhibit crop growth, yield, and quality worldwide. Allotetraploid rapeseed (Brassica napus L.), a major glycophyte oil crop, is susceptible to salinity. Understanding the physiological and molecular strategies of rapeseed salinity resistance is a promising and cost-effective strategy for developing highly resistant cultivars., Results: First, early leaf senescence was identified and root system growth was inhibited in rapeseed plants under severe salinity conditions. Electron microscopic analysis revealed that 200 mM NaCl induced fewer leaf trichomes and stoma, cell plasmolysis, and chloroplast degradation. Primary and secondary metabolite assays showed that salinity led to an obviously increased anthocyanin, osmoregulatory substances, abscisic acid, jasmonic acid, pectin, cellulose, reactive oxygen species, and antioxidant activity, and resulted in markedly decreased photosynthetic pigments, indoleacetic acid, cytokinin, gibberellin, and lignin. ICP-MS assisted ionomics showed that salinity significantly constrained the absorption of essential elements, including the nitrogen, phosphorus, potassium, calcium, magnesium, iron, mangnese, copper, zinc, and boron nutrients, and induced the increase in the sodium/potassium ratio. Genome-wide transcriptomics revealed that the differentially expressed genes were involved mainly in photosynthesis, stimulus response, hormone signal biosynthesis/transduction, and nutrient transport under salinity., Conclusions: The high-resolution salt-responsive gene expression profiling helped the efficient characterization of central members regulating plant salinity resistance. These findings might enhance integrated comprehensive understanding of the morpho-physiologic and molecular responses to salinity and provide elite genetic resources for the genetic modification of salinity-resistant crop species.

Improving crop nitrogen (N) limitation adaptation (NLA) is a core approach to enhance N use efficiency (NUE) and reduce N fertilizer application. Rapeseed has a high demand for N nutrients for optimal plant growth and seed production, but it exhibits low NUE. Epigenetic modification, such as DNA methylation and modification from small RNAs, is key to plant adaptive responses to various stresses. However, epigenetic regulatory mechanisms underlying NLA and NUE remain elusive in allotetraploid B. napus . In this study, we identified overaccumulated carbohydrate, and improved primary and lateral roots in rapeseed plants under N limitation, which resulted in decreased plant nitrate concentrations, enhanced root-to-shoot N translocation, and increased NUE. Transcriptomics and RT-qPCR assays revealed that N limitation induced the expression of NRT1.1 , NRT1.5 , NRT1.7 , NRT2.1/NAR2.1 , and Gln1;1 , and repressed the transcriptional levels of CLCa , NRT1.8 , and NIA1 . High-resolution whole genome bisulfite sequencing characterized 5094 differentially methylated genes involving ubiquitin-mediated proteolysis, N recycling, and phytohormone metabolism under N limitation. Hypermethylation/hypomethylation in promoter regions or gene bodies of some key N-metabolism genes might be involved in their transcriptional regulation by N limitation. Genome-wide miRNA sequencing identified 224 N limitation-responsive differentially expressed miRNAs regulating leaf development, amino acid metabolism, and plant hormone signal transduction. Furthermore, degradome sequencing and RT-qPCR assays revealed the miR827-NLA pathway regulating limited N-induced leaf senescence as well as the miR171- SCL6 and miR160- ARF17 pathways regulating root growth under N deficiency. Our study provides a comprehensive insight into the epigenetic regulatory mechanisms underlying rapeseed NLA, and it will be helpful for genetic engineering of NUE in crop species through epigenetic modification of some N metabolism-associated genes.

Soil salinity is a main abiotic stress in agriculture worldwide. The Na + /H + antiporters (NHXs) play pivotal roles in intracellular Na + excretion and vacuolar Na + compartmentalization, which are important for plant salt stress resistance (SSR). However, few systematic analyses of NHXs has been reported in allotetraploid rapeseed so far. Here, a total of 18 full-length NHX homologs, representing seven subgroups (NHX1-NHX8 without NHX5), were identified in the rapeseed genome (A n A n C n C n ). Number variations of BnaNHXs might indicate their significantly differential roles in the regulation of rapeseed SSR. BnaNHXs were phylogenetically divided into three evolutionary clades, and the members in the same subgroups had similar physiochemical characteristics, gene/protein structures, and conserved Na + transport motifs. Darwin´s evolutionary pressure analysis suggested that BnaNHXs suffered from strong purifying selection. The cis-element analysis revealed the differential transcriptional regulation of NHXs between the model Arabidopsis and B. napus. Differential expression of BnaNHXs under salt stress, different nitrogen forms (ammonium and nitrate), and low phosphate indicated their potential involvement in the regulation of rapeseed SSR. Global landscapes of BnaNHXs will give an integrated understanding of their family evolution and molecular features, which will provide elite gene resources for the genetic improvement of plant SSR through regulating the NHX-mediated Na + transport., Competing Interests: The authors declare no conflict of interest.

Background: Nitrogen (N), referred to as a "life element", is a macronutrient essential for optimal plant growth and yield production. Amino acid (AA) permease (AAP) genes play pivotal roles in root import, long-distance translocation, remobilization of organic amide-N from source organs to sinks, and other environmental stress responses. However, few systematic analyses of AAPs have been reported in Brassica napus so far., Results: In this study, we identified a total of 34 full-length AAP genes representing eight subgroups (AAP1-8) from the allotetraploid rapeseed genome (A n A n C n C n , 2n = 4x = 38). Great differences in the homolog number among the BnaAAP subgroups might indicate their significant differential roles in the growth and development of rapeseed plants. The BnaAAPs were phylogenetically divided into three evolutionary clades, and the members in the same subgroups had similar physiochemical characteristics, gene/protein structures, and conserved AA transport motifs. Darwin's evolutionary analysis suggested that BnaAAPs were subjected to strong purifying selection pressure. Cis-element analysis showed potential differential transcriptional regulation of AAPs between the model Arabidopsis and B. napus. Differential expression of BnaAAPs under nitrate limitation, ammonium excess, phosphate shortage, boron deficiency, cadmium toxicity, and salt stress conditions indicated their potential involvement in diverse nutrient stress responses., Conclusions: The genome-wide identification of BnaAAPs will provide a comprehensive insight into their family evolution and AAP-mediated AA transport under diverse abiotic stresses. The molecular characterization of core AAPs can provide elite gene resources and contribute to the genetic improvement of crop stress resistance through the modulation of AA transport.

Oilseed rape (Brassica napus) has great potential for phytoremediation of cadmium (Cd)-polluted soils due to its large plant biomass production and strong metal accumulation. Enhanced plant Cd resistance (PCR) is a crucial prerequisite for phytoremediation through hyper-accumulation of excess Cd. However, the complexity of the allotetraploid genome of rapeseed hinders our understanding of PCR. To explore rapeseed Cd-resistance mechanisms, we examined two genotypes, 'ZS11' (Cd-resistant) and 'W10' (Cd-sensitive), that exhibit contrasting PCR while having similar tissue Cd concentrations, and characterized their different fingerprints in terms of plant morphophysiology (electron microscopy), ion abundance (inductively coupled plasma mass spectrometry), DNA variation (whole-genome resequencing), transcriptomics (high-throughput mRNA sequencing), and metabolomics (ultra-high performance liquid chromatography-mass spectrometry). Fine isolation of cell components combined with ionomics revealed that more Cd accumulated in the shoot vacuoles and root pectins of the resistant genotype than in the sensitive one. Genome and transcriptome sequencing identified numerous DNA variants and differentially expressed genes involved in pectin modification, ion binding, and compartmentalization. Transcriptomics-assisted gene co-expression networks characterized BnaCn.ABCC3 and BnaA8.PME3 as the central members involved in the determination of rapeseed PCR. High-resolution metabolic profiles revealed greater accumulation of shoot Cd chelates, and stronger biosynthesis and higher demethylation of root pectins in the resistant genotype than in the sensitive one. Our comprehensive examination using a multiomics approach has greatly improved our understanding of the role of subcellular reallocation of Cd in the determination of PCR., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Boron (B) is an essential micronutrient for the growth and development of plants. Oilseed rape (Brassica napus L.) is a staple oleaginous crop, which is greatly susceptible to B deficiency. Significant differences in tolerance of low-B stresses are observed in rapeseed genotypes, but the underlying mechanism remains unclear, particularly at the single-cell level. Here we provide novel insights into pectin-mediated cell wall (CW) mechanical properties implicated in the differential tolerance of low B in rapeseed genotypes. Under B deficiency, suspension cells of the low-B-sensitive genotype 'W10' showed more severely deformed morphology, lower viabilities and a more easily ruptured CW than those of the low-B-tolerant genotype 'QY10'. Cell rupture was attributed to the weakened CW mechanical strength detected by atomic force microscopy; the CW mechanical strength of 'QY10' was reduced by 13.6 and 17.4%, whereas that of 'W10' was reduced by 29.0 and 30.4% under 0.25 and 0.10 μM B conditions, respectively. The mechanical strength differences between 'QY10' and 'W10' were diminished after the removal of pectin. Further, 'W10' exhibited significantly higher pectin concentrations with much more rhamnogalacturonan II (RG-II) monomer, and also presented obviously higher mRNA abundances of pectin biosynthesis-related genes than 'QY10' under B deficiency. CW regeneration was more difficult for protoplasts of 'W10' than for those of 'QY10'. Taking the results together, we conclude that the variations in pectin-endowed CW mechanical properties play key roles in modulating the differential genotypic tolerance of rapeseed to low-B stresses at both the single-cell and the plant level, and this can potentially be used as a selection trait for low-B-tolerant rapeseed breeding., (© The Author 2017. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Allotetraploid rapeseed (Brassica napus L., An An Cn Cn , 2n = 4x = 38) is extraordinarily susceptible to boron (B) deficiency, a ubiquitous problem causing severe losses in seed yield. The breeding of B-efficient rapeseed germ plasm is a cost-effective and environmentally friendly strategy for the agricultural industry; however, genes regulating B efficiency in allotetraploid rapeseed have not yet been isolated. In this research, quantitative trait locus (QTL) fine mapping and digital gene expression (DGE) profiling were combined to identify the candidate genes underlying the major-effect QTL qBEC-A3a, which regulates B efficiency. Comparative phenotype analyses of the near-isogenic lines (NILs) indicated that qBEC-A3a plays a significant role in improving B efficiency under B deficiency. Exploiting QTL fine mapping and DGE analyses revealed a nodulin 26-like intrinsic protein (NIP) gene, which encodes a likely boric acid channel. The gene co-expression network for putative B transporters also highlighted its central role in the efficiency of B uptake. An integration of whole-genome re-sequencing (WGS) with bulked segregant analysis (BSA) authenticated the emerging availability of QTL-seq for the QTL analyses in allotetraploid rapeseed. Transcriptomics-assisted QTL mapping and comparative genomics provided novel insights into the rapid identification of quantitative trait genes (QTGs) in plant species with complex genomes., (© 2016 John Wiley & Sons Ltd.)

Proline accumulation is an important metabolic adaptative mechanism of plants under biotic and abiotic stress. P5CS, P5CR, PDH, and P5CDH are key enzymes in the glutamate-dependent proline biosynthesis pathway. Rapeseed, an important oil crop in the world, is often subjected to various biotic and abiotic stresses during its growth and development. However, no systematic analysis of these proline metabolic gene families has been reported in Brassica napus so far. In this study, 10 BnaP5CSs, 6 BnaP5CRs, 8 BnaPDHs, and 3 BnaP5CDHs were identified by using the genomic annotation information of 'Zhongshuang 11'. Phylogenetically, these gene families were divided into different evolutionary branches, and members of the same subgroups had similar physical and chemical properties, gene / protein structure, and conserved motifs. Evolutionary pressure analysis showed that these genes were subjected to strong purification selection. Cis-acting element analysis revealed that there were common and specific transcriptional regulatory mechanisms among the four kinds of gene families. In this study, rapeseed seedlings were respectively treated with salt stress, low potassium (K), low phosphate (P), and ammonium toxicity, and both shoots and roots were respectively sampled for transcriptomic analysis. The results indicated that the relative expression levels of genes related to proline synthesis were generally up-regulated under the above-mentioned four stresses, whereas the relative expression levels of genes regulating proline degradation were down-regulated under salt and low P stresses. Gene co-expression network analysis demonstrated that BnaC4.P5CS1a and BnaA5.P5CS1 might play central roles in the proline-mediated stress responsive networks in rapeseed. Through bioinformatics identification of proline metabolism gene family and analysis of transcription characteristics under various abiotic stresses, this study will provide a theoretical basis for further study of proline-mediated stress resistance, and will also provide excellent gene resources for genetic improvement of abiotic stress resistance mediated by proline metabolism in Brassica napus. [ABSTRACT FROM AUTHOR]

Brassica napus L. is one of the important oil crops in the world. However soil salt stress severely inhibited its growth and development. Previous studies have shown that under salt stress, plants increase their own salt stress resistance by expressing some miRNAs and regulating the expression of their target genes. In this study, rapeseed was cultured under 200 mmol⋅L-1 NaCl treatment and control, and took the shoot and root to construct 12 small RNA libraries for high-throughput sequencing. Through the differential expression analysis of miRNAs in the whole genome, a total of 26 differentially expressed miRNAs were identified and 171 corresponding target genes were predicted. Combining the differential expression of genes in the early transcriptome and the results of the differential expression of miRNAs in this study, it is speculated that miRNA156-SPL15-WRKY, miRNA397-LAC12-xylogen, miR169-NFYA5 and miR399-UBC29-ubiquitination pathways might be involved in the regulation of salt stress resistance in B. napus. [ABSTRACT FROM AUTHOR]

Tobacco viruses transmitted by green peach aphids, Myzus persicae (Sulzer) (Hemiptera: Aphididae), cause severe disease in flue‐cured tobacco, Nicotiana tabacum L. (Solanaceae), in China and throughout the world. Field experiments were conducted in 2016 and 2017 in Longyan City, Fujian Province, China, to determine whether M. persicae and aphid‐transmitted virus diseases are affected by intercropping of oilseed rape, Brassica napus L. (Brassicaceae), in tobacco fields. The results showed that, compared with those in monocultured fields, the densities of M. persicae and winged aphids in intercropped fields significantly decreased in both 2016 and 2017. In particular, the appearance of winged aphids was delayed by ca. 7 days. Moreover, the densities of Aphidius gifuensis Ashmead (Hymenoptera: Aphidiidae), a parasitoid of the aphid, significantly increased in 2016 and 2017. Accordingly, the incidence rates of aphid‐transmitted virus diseases (those caused by the cucumber mosaic virus, potato virus Y, and tobacco etch virus) significantly decreased in the intercropped fields in 2016 and 2017. Tobacco yields and monetary value significantly increased in 2016 (by 10–25 and 14–29%, respectively) and 2017 (by 17–22 and 22–34%, respectively). Consequently, our results suggest that intercropping oilseed rape in tobacco fields is a good approach to regulating and controlling aphids and tobacco mosaic viruses, for example potyvirus, and this intercropping can help control aphid‐transmitted virus diseases in tobacco. [ABSTRACT FROM AUTHOR]