In recent years, the spread of clubroot disease caused by Plasmodiophora brassicae infection has seriously affected the yield and quality of Brassica juncea (L.) Czern.. The cascade of mitogen-activated protein kinases (MAPKs), a highly conserved signaling pathway, plays an important role in plant responses to both biotic and abiotic stress conditions. To mine the MAPK genes related to clubroot disease resistance in B. juncea, we conducted a genome-wide analysis on this vegetable, and we analyzed the phylogenetic evolution and gene structure of the MAPK gene family in mustard. The 66 BjuMAPK genes identified by screening the whole genome sequence of B. juncea were unevenly distributed on 17 chromosomes. At the genomic scale, tandem repeats led to an increase in the number of MAPK genes in B. juncea. It was found that members of the same subfamily had similar gene structures, and there were great differences among different subfamilies. These predicted cis-acting elements were related to plant hormones, stress resistance, and plant growth and development. The expression of BjuMAPK02, BjuMAPK15, BjuMAPK17, and BjuMAPK19 were down-regulated or up-regulated in response to P. brassicae infection. The above results lay a theoretical foundation for further studying the functions of BjuMAPK genes in B. juncea in response to the biotic stress caused by clubroot disease.
Mustard Plant/parasitology* ; Plasmodiophorida/pathogenicity* ; Plant Diseases/genetics* ; Mitogen-Activated Protein Kinases/metabolism* ; Phylogeny ; Disease Resistance/genetics* ; Gene Expression Regulation, Plant ; Genome, Plant ; Plant Proteins/genetics*

Flowering and bolting are important agronomic traits in cruciferous crops such as Brassica juncea. Timely flowering can ensure the crop organ yield and quality, as well as seed propagation. The WRKY family plays an important role in regulating plant bolting and flowering, while the function and mechanism of WRKY12 in B. juncea remain unknown. To explore its function and mechanism in bolting and flowering of B. juncea, we cloned and characterized the BjuWRKY12 gene in B. juncea and found that its expression levels were significantly higher in flowers and inflorescences than in leaves. BjuWRKY12 belonged to the Ⅱc subfamily of the WRKY family, and subcellular localization indicated that the protein was located in the nucleus. Ectopic overexpression of BjuWRKY12 in transgenic lines promoted bolting and flowering, leading to significant increases in the expression levels of flowering integrators SOC1 and FUL. Furthermore, yeast one-hybrid and dual luciferase reporter system assays confirmed that BjuWRKY12 directly bound to the promoters of BjuSOC1 and BjuFUL, undergoing protein-DNA interactions. This discovery gives new insights into the regulation network and molecular mechanisms of BjuWRKY12, laying a theoretical foundation for the breeding of high-yield and high-quality varieties of B. juncea.
Mustard Plant/metabolism* ; Flowers/growth & development* ; Plant Proteins/physiology* ; Promoter Regions, Genetic/genetics* ; Gene Expression Regulation, Plant ; Plants, Genetically Modified/genetics* ; Transcription Factors/metabolism* ; MADS Domain Proteins/metabolism*

The WUSCHEL related-homeobox (WOX) family is one of the plant-specific transcription factor families, playing important roles in plant growth and development. In this study, 51 WOX gene family members were identified from the genome data of Brassica juncea by searching and screening with HUMMER, Smart and other software. Their protein molecular weight, amino acids numbers, and isoelectric point were analyzed by using Expasy online software. Furthermore, bioinformatics software was used to systematically analyze the evolutionary relationship, conservative region, and gene structure of the WOX gene family. The mustard WOX gene family was divided into three subfamilies: ancient clade, intermediate clade, and WUS clade/modern clade. Structural analysis showed that the type, organization form and gene structure of the conservative domain of WOX transcription factor family members in the same subfamily were highly consistent, while there was a certain diversity among different subfamilies. 51 WOX genes are distributed unevenly on 18 chromosomes of mustard. Most of the promoters of these genes contain cis acting elements related to light, hormone and abiotic stress. Using transcriptome data and real-time fluorescence quantitative PCR (qRT-PCR) analysis, it was found that the expression of mustard WOX gene was spatio-temporal specific, among which BjuWOX25, BjuWOX33, and BjuWOX49 might play an important role in the development of silique, and BjuWOX10, BjuWOX32, and BjuWOX11, BjuWOX23 respectively might play an important role in the response to drought and high temperature stresses. The above results may facilitate the functional study of mustard WOX gene family.
Mustard Plant/genetics* ; Multigene Family/genetics* ; Transcription Factors/metabolism* ; Plants/genetics* ; Promoter Regions, Genetic ; Phylogeny ; Gene Expression Regulation, Plant ; Plant Proteins/metabolism*

Brassica juncea is a yearly or biennial vegetable in Brassica of Cruciferae. The yield and quality of its product organs are affected by flowering time. WRKY proteins family can respond to biological and abiotic stresses, developmental regulation and signal transduction. WRKY75 is an important member of WRKY family which can regulate flowering, but the flowering regulation mechanism in B. juncea has not been reported. In this study, a gene BjuWRKY75 in B. juncea was cloned, and the encoded-protein belonged to the group Ⅱ of WRKY protein with highly conserved domain. BjuWRKY75 had the highest homology with BriWRKY75 of Brassica nigra. The relative expression level of BjuWRKY75 in flowers was significantly higher than that in leaves and stems, and it was expressed stably in leaves. BjuWRKY75 protein was localized in the nucleus and interacted with the promoter of the flowering integrator BjuFT, which contained the W-box response element for the interaction between protein and DNA. Thus, it could transcriptionally activate the expression of the downstream genes. The overexpression of BjuWRKY75 in Arabidopsis led to earlier flowering significantly. In conclusion, BjuWRKY75 could directly target the promoter of BjuFT and accelerate flowering. These results may facilitate further study on the regulation of flowering molecules of BjuWRKY75.
Arabidopsis/genetics* ; Flowers/genetics* ; Gene Expression Regulation, Plant ; Mustard Plant/genetics* ; Plant Proteins/metabolism* ; Promoter Regions, Genetic

HDA9, a member of the deacetylase family, plays a vital role in regulating plant flowering time through flowering integrator SOC1 and AGL24. However, it remains elusive how HDA9 interacts with SOC1 and AGL24 in flowering time control. Here, HDA9 was cloned in Brassica juncea and then its three active sites were separately replaced with Ala via overlap extension PCR. Thus, mutants of HDA9(D172A), HDA9(H174A) and HDA9(D261A) were constructed and fused into the pGADT7 vector. The yeast one-hybrid assays indicated that HDA9 mutants remained the interactions with the promoters of SOC1 and AGL24. Furthermore, the aforementioned results were confirmed in the dual luciferase assays. Interestingly, the DNA-protein interactions were weakened significantly due to the mutation in the three active sites of HDA9. It suggested that flowering signal integrator SOC1 and AGL24 were regulated by the key amino acid residues of 172th, 174th and 261th in HDA9. Our results provide valuable information for the in-depth study of the biological function and molecular regulation of HDA9 in Brassica juncea flowering time control.
Flowers ; genetics ; Gene Expression Regulation, Plant ; genetics ; Mustard Plant ; enzymology ; genetics ; Mutation ; Plant Proteins ; genetics ; metabolism ; Promoter Regions, Genetic ; genetics

In order to broaden Chinese cabbage gene pool, we conducted interspecific somatic hybridization between Chinese cabbage (Brassica campestris, 2n=20, AA) and Cabbage (B. oleracea, 2n=18, CC). Protoplasts were isolated from 10-day-old cotyledons and hypocotyls of young seedlings, and fused by 40% polyethylene glycol (PEG). Fused cells were cultured in modified K8p liquid medium supplemented with some plant growth regulators. Fusion products were characterized by their morphological, cytological and molecular biological traits. The results showed that, a total of 35 regenerated green plants were obtained from 320 calli, the plant regeneration frequency was 10.94%, and eleven of which were survived in greenhouse. All regenerants were true hybrids as confirmed by randomly amplified polymorphic DNA (RAPD) and genomic in situ hybridization (GISH) analysis. Ploidy levels of hybrid plants were determined by chromosome counting and flow cytometry. The sum of the chromosome number (2n = 38) from the two fusion patents were found in 36.4% of regeneratns; another 36.4% had chromosomes range to 58-60; 27.2% had more chromosomes ranges to 70-76. All regenerated plants produced normal flowers. We investigated the pollen fertility and seed set after self-pollination and backcrossing with the parental species. For hybrids with chromosomes more than 38 it was possible to obtain some seeds when they after self-pollination. Within the group of hybrids with 38 chromosomes, seed set were very variable, only 0.11 seeds per pod by self-pollination, 0.23-0.76 by open-pollination, 0.02-0.04 by backcrossing with Chinese cabbage. Progeny lines obtained by self-pollination had larger leaves and leaf shapes intermediate of the parental species. Pollen fertility was gradually recovered in the first and second progenies. The backcrossing progeny lines, as a whole, exhibited morphologies were similar to Chinese cabbage. Morphological variations were observed among the somatic hybrids and their progenies.
Brassica napus ; genetics ; growth & development ; Breeding ; Chromosomes, Plant ; Hybridization, Genetic ; genetics ; Mustard Plant ; genetics ; growth & development ; Plant Somatic Embryogenesis Techniques ; Ploidies ; Pollen ; physiology ; Protoplasts ; cytology ; Random Amplified Polymorphic DNA Technique ; Recombination, Genetic

Plant Dicer-like (DCL) and Argonaute (AGO) are the key enzymes involved in anti-virus post-transcriptional gene silencing (AV-PTGS). Here we show that AV-PTGS exhibited nucleotide preference by calculating a relative AV-PTGS efficiency on processing viral RNA substrates. In comparison with genome sequences of dicot-infecting Turnip mosaic virus (TuMV) and monocot-infecting Cocksfoot streak virus (CSV), viral-derived small interfering RNAs (vsiRNAs) displayed positive correlations between AV-PTGS efficiency and G+C content (GC%). Further investigations on nucleotide contents revealed that the vsiRNA populations had G-biases. This finding was further supported by our analyses of previously reported vsiRNA populations in diverse plant-virus associations, and AGO associated Arabidopsis endogenous siRNA populations, indicating that plant AGOs operated with G-preference. We further propose a hypothesis that AV-PTGS imposes selection pressure(s) on the evolution of plant viruses. This hypothesis was supported when potyvirus genomes were analysed for evidence of GC elimination, suggesting that plant virus evolution to have low GC% genomes would have a unique function, which is to reduce the host AV-PTGS attack during infections.
Arabidopsis ; enzymology ; genetics ; virology ; Base Composition ; Dactylis ; enzymology ; genetics ; virology ; Genes, Plant ; Genes, Viral ; Models, Genetic ; Mustard Plant ; enzymology ; genetics ; virology ; Plant Diseases ; genetics ; virology ; Plant Proteins ; metabolism ; Plant Viruses ; genetics ; pathogenicity ; Plants ; enzymology ; genetics ; virology ; Potyvirus ; genetics ; pathogenicity ; RNA Interference ; RNA, Plant ; genetics ; RNA, Small Interfering ; chemistry ; genetics ; metabolism ; RNA, Viral ; chemistry ; genetics ; metabolism ; RNA-Induced Silencing Complex ; metabolism ; Ribonuclease III ; metabolism ; Selection, Genetic ; Substrate Specificity

The proteins encoded by the Brassica juncea chitinase gene BjCHI1 and its derived genes BjCHI2 and BjCHI3 were expressed by Multi-copy Pichia expression system. The chitinase activity of FPLC purified BjCHI1, BjCHI2 and BjCHI3 were tested and the results showed that all the three proteins degraded both CM-chitin-RBV and colloidal chitin. The Km values of BjCHI1, BjCHI2 and BjCHI3 for CM-chitin-RBV were estimated as 0.799 mg/mL, 0.544 mg/mL and 0.793 mg/mL, respectively. When the colloidal chitin was used as substrate, the Km values were 0.281 mg/mL, 0.388 mg/mL and 1.643 mg/mL, respectively, indicating chitin-binding domain can increase affinity of chitinase to insoluble substrate. In the agglutination activity assay, only BjCHI1 shows activity when the protein concentration was more than 33 micrograms/mL, while BjCHI2 and BjCHI3 without agglutination activity even when the concentration was increased as high as 800 micrograms/mL. This means that the two chitin-binding domains in BjCHI1 are essential for agglutination and BjCHI1 is the first protein which shows both chitinase and agglutination activity identified so far in plants.
Agglutination ; Agglutinins ; genetics ; Chitinases ; genetics ; isolation & purification ; physiology ; Mustard Plant ; chemistry ; Pichia ; genetics ; Plant Proteins ; genetics ; Plasmids ; Polymerase Chain Reaction ; Recombinant Proteins ; biosynthesis ; isolation & purification