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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]

Plant architecture is the determining factor of yield in many crops. Rapeseed (Brassica napus) is an important oilseed crop worldwide, but the genetic basis underlying plant architecture in this species remains elusive. Here, we characterized the dwarf mutant dwarf and compact 1 (dac1) from an ethyl methanesulfonate (EMS) mutagenized population of rapeseed cv. Zhongshuang 11 (ZS11). dac1 has multiple morphological defects, such as dwarfism, narrow branch angles, delayed flowering, and dark-green, crinkled leaves. We identified the underlying gene, which encodes a glycogen synthase kinase 3 (GSK3)-like protein homologous to Arabidopsis thaliana BRASSINOSTEROID-INSENSITIVE 2 (BIN2)-LIKE 1 (BIL1), and named this gene BnaC04. BIL1. A C-to-T mutation in BnaC04. BIL1 changes proline at position 314 of the encoded protein to leucine (P314L), affecting the degradation of BnaC04. BIL1, and which represses plant architecture in a dosage-dependent manner via brassinosteroid signaling. We identified an 11-bp core sequence and one pivotal base in the promoter region of BnaC04. BIL1 that affect its expression. Importantly, heterozygotes of dac1 displayed single-locus overdominance, resembling a proposed ideotype for rapeseed. Our findings demonstrate that a gain-of-function mutation in BnaC04. BIL1 contributes to ideal plant architecture, representing a valuable resource for rapeseed breeding. • The dwarf rapeseed mutant dac1 displayed multiple morphological defects, such as delayed flowering and crinkled leaves. • A GSK3-like protein was identified as the underlying gene to dac1 morphological defects. • The heterozygotes of dac1 resembled a proposed ideotype for rapeseed 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]