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Background and aims: Magnesium (Mg) deficiency impacts many metabolic processes in Brassica napus (B. napus), leading to yield loss. However, the mechanism of Mg2+ uptake and translocation in B. napus remains unknown. Methods: After screening 39 genotypes of B. napus under Mg-deficient conditions, the cultivars P160 and P153 were selected according to their Mg transfer factor (TF) from root to shoot. We further characterized these two genotypes under Mg-deficiency by analyzing chlorophyll concentration, malondialdehyde and peroxidase activity, and reducing sugar concentration in leaves. Additionally, we performed transcriptomics and qRT-PCR assays on P153 and P160 shoots and roots. The identified functional genes involved in Mg transport were characterized by functional assays in yeast and Arabidopsis mutants. Results: The physiological analysis revealed that P160 (Mg tolerance cultivar; Mg-T) is more tolerant than P153 (Mg sensitive cultivar; Mg-S) under magnesium-deficient environments. Transcriptomics and qRT-PCR assays revealed that transcript levels of BnMGT1–2 and BnMGT6–1 were more significantly up-regulated in the shoot of Mg-T cultivar than that of the Mg-S cultivar under Mg limitation. Functional assays of BnMGT1–2 and BnMGT6–1 reveals that BnMGT1–2 and BnMGT6–1 are the two main functional Mg transporters mediating Mg translocation from root to shoot under low Mg conditions. Conclusion: Mg-T is more efficient in the translocation of Mg from root to shoot than Mg-S. BnMGT1–2 and BnMGT6–1 should be the two main Mg transporters associated with Mg translocation under Mg deficiency condition, which caused the different Mg efficiency between the Mg-T and Mg-S. [ABSTRACT FROM AUTHOR]

Aims: Cadmium (Cd) is the most widespread toxic heavy metal to plant growth. As the second leading oil crop, some genotypes of Brassica napus (B. napus) are potential Cd accumulators. However, the Cd translocation mechanism from root to shoot in B. napus in response to Cd toxicity remains unknown. Methods: In the present study, a couple of B. napus genotypes with contrasting Cd uptake and root-to-shoot translocation abilities, named P78 (the high Cd accumulator, HC) and P72 (the low Cd accumulator, LC), were chosen from 39 B. napus genotypes with various Cd accumulation features. Results: Physiological comparison of P78 and P72 reveals that P72 is more sensitive to Cd toxicity than P78. With genomic resequencing, transcriptomics and qRT-PCR assay, BnNramp2;1 and BnNramp4;2 were focused with highly upregulation in shoot of P78 under Cd treatment condition. Furthermore, BnNramp2;1 and BnNramp4;2 can successfully complement the function of tonoplast localized Cd transporter YCF1. And when BnNramp2;1 and BnNramp4;2 were transferred in Arabidopsis atnramp mutants, the transgenic plants showed better growth rate than mutants under higher Cd stress conditions. Conclusions: The results reveals that BnNramp2;1 and BnNramp4;2 were two main Cd transporters associated with enhanced root-to-shoot translocation and accumulation of Cd in shoot of B. napus. [ABSTRACT FROM AUTHOR]

Rapeseed (Brassica napus) is a major edible oilseed crop consumed worldwide. However, its yield is seriously affected by infection from the broad-spectrum non-obligate pathogen Sclerotinia sclerotiorum due to a lack of highly resistant germplasm. Here, we identified a Sclerotinia -resistant and light-dependent lesion mimic mutant from an ethyl methanesulfonate-mutagenized population of the rapeseed inbred Zhongshuang 11 (ZS11) named lesion mimic mutant 1 (lmm1). The phenotype of lmm1 is controlled by a single recessive gene, named LESION MIMIC MUTANT 1 (LMM1), which mapped onto chromosome C04 by bulked segregant analysis within a 2.71-Mb interval. Histochemical analysis indicated that H2O2 strongly accumulated and cell death occurred around the lesion mimic spots. Among 877 differentially expressed genes (DEGs) between ZS11 and lmm1 leaves, 188 DEGs were enriched in the defense response, including 95 DEGs involved in systemic acquired resistance, which is consistent with the higher salicylic acid levels in lmm1. Combining bulked segregant analysis and transcriptome analysis, we identified a significantly up-regulated gene, BnaC4.PR2 , which encodes β-1,3-glucanase, as the candidate gene for LMM1. Overexpression of BnaC4.PR2 may induce a reactive oxygen species burst to trigger partial cell death and systemic acquired resistance. Our study provides a new genetic resource for S. sclerotiorum resistance as well as new insights into disease resistance breeding in B. napus. [ABSTRACT FROM AUTHOR]

Background: In the oilseed crop Brassica napus (rapeseed), various metabolic processes influence seed oil content, oil quality, and biological yield. However, the role of plastid membrane proteins in these traits has not been explored. Results: Our genome-wide association study (GWAS) of 520 B. napus accessions identified the chloroplast membrane protein-localized FATTY ACID EXPORTER 1-1 (FAX1-1) as a candidate associated with biological yield. Seed transcript levels of BnaFAX1-1 were higher in a cultivar with high seed oil content relative to a low-oil cultivar. BnaFAX1-1 was localized to the plastid envelope. When expressed in Arabidopsis thaliana, BnaFAX1-1 enhanced biological yield (total plant dry matter), seed yield and seed oil content per plant. Likewise, in the field, B. napus BnaFAX1-1 overexpression lines (BnaFAX1-1-OE) displayed significantly enhanced biological yield, seed yield, and seed oil content compared with the wild type. BnaFAX1-1 overexpression also up-regulated gibberellic acid 4 (GA4) biosynthesis, which may contribute to biological yield improvement. Furthermore, oleic acid (C18:1) significantly increased in BnaFAX1-1 overexpression seeds. Conclusion: Our results indicated that the putative fatty acid exporter BnaFAX1-1 may simultaneously improve seed oil content, oil quality and biological yield in B. napus, providing new approaches for future molecular breeding. [ABSTRACT FROM AUTHOR]

Rapeseed is one of the most important oilseeds crops worldwide. Although stem development greatly affects crop yield, its molecular mechanisms remain elusive in rapeseed. This study found a stem bending 1 (stb1) mutant in rapeseed with abnormal stem development and performed phenotype characterization, genetic analysis, quantitative trait locus mapping, and transcriptome analysis. The key stage of stem bending in stb1 mutant occurred at Biologische Bundesanstalt, Bundessortenamt and CHemical industry (BBCH) stages 59–61, from the end of stem elongation to early flowering. The number of vessels and the degree of development of stem xylem, sclerenchyma, and parenchyma cells were extremely lower in stb1 mutant than in elite cultivar ZS11. Genetic analysis revealed that stb1 is controlled by a single recessive locus located between markers Bn-A01-p2421445 and Bn-A01-p4230829 on chromosome A01. Using RNA-seq, identified 1631 genes that differentially expressed between mutant and normal F 2 plants in the shoot apical meristem and stem. The down-regulated genes were mainly overrepresented in auxin transport and coenzyme metabolism processes. Combining data on the auxin concentrations in stem and expression of candidate genes within the mapping interval in the mutant, it was speculated that the phenotype of the stb1 mutant may be caused by defects in polar auxin transport, as two auxin transport-related genes were obviously down-regulated in the mutant. Among them, BnSOS3-INTERACTING PROTEIN3 , which encodes a CBL-interacting protein kinase, was considered the most promising candidate gene for further investigation. These results lay a foundation for better understanding the molecular mechanisms of stem development in rapeseed. • Abnormal stem development of a stem bending 1 (stb1) mutant was found in rapeseed at the BBCH stages 59 to 61. • The stb1 is controlled by a single recessive locus located between markers Bn-A01-p2421445 and Bn-A01-p4230829. • The phenotype of stb1 may be caused by mutation of BnSOS3-INTERACTING PROTEIN3 that controls polar auxin transport. [ABSTRACT FROM AUTHOR]

Background: Increasing seed oil content is one of the most important targets for rapeseed (Brassica napus) breeding. However, genetic mechanisms of mature seed oil content in Brassica napus (B. napus) remain little known. To identify oil content-related genes, a genome-wide association study (GWAS) was performed using 588 accessions. Results: High-throughput genome resequencing resulted in 385,692 high-quality single nucleotide polymorphism (SNPs) with a minor allele frequency (MAF) > 0.05. We identified 17 loci that were significantly associated with seed oil content, among which 12 SNPs were distributed on the A3 (11 loci) and A1 (one loci) chromosomes, and five novel significant SNPs on the C5 (one loci) and C7 (four loci) chromosomes, respectively. Subsequently, we characterized differentially expressed genes (DEGs) between the seeds and silique pericarps on main florescences and primary branches of extremely high- and low-oil content accessions (HO and LO). A total of 64 lipid metabolism-related DEGs were identified, 14 of which are involved in triacylglycerols (TAGs) biosynthesis and assembly. Additionally, we analyzed differences in transcription levels of key genes involved in de novo fatty acid biosynthesis in the plastid, TAGs assembly and lipid droplet packaging in the endoplasmic reticulum (ER) between high- and low-oil content B. napus accessions. Conclusions: The combination of GWAS and transcriptome analyses revealed seven candidate genes located within the confidence intervals of significant SNPs. Current findings provide valuable information for facilitating marker-based breeding for higher seed oil content in B. napus. [ABSTRACT FROM AUTHOR]