MADS-box genes play important roles in vegetative growth and reproductive development and are essential for the correct development of plants (particularly inflorescences, flowers, and fruits). However, this gene family has not been identified nor their functions analyzed in Brassica oleracea. In this study, we performed a whole-genome survey of the complete set of MADS-box genes in B. oleracea. In total, 91 MADS-box transcription factors (TFs) were identified and categorized as type I (Mα, Mβ, Mγ) and type II (MIKCC, MIKC*) groups according to the phylogeny and gene structure analysis. Among these genes, 59 were randomly distributed on 9 chromosomes, while the other 23 were assigned to 19 scaffolds and 9 genes from NCBI had no location information. Both RNA-sequencing and quantitative real-time-PCR analysis suggested that MIKC genes had more active and complex expression patterns than M type genes and most type II genes showed high flowering-related expression profiles. Additional quantitative real-time-PCR analysis of pedicel and four flower whorls revealed that the structure of the B.oleracea MIKC genes was conserved, but their homologues showed variable expression patterns compared to those in Arabidopsis thaliana. This paper gives a detailed overview of the BolMADS genes and their expression patterns. The results obtained in this study provide useful information for understanding the molecular regulation of flower development and further functional characterization of MADS-box genes in B. oleracea.

Glucosinolates (GSLs) are a group of sulfur-containing secondary metabolites, which are abundant in Brassica vegetables. GSL breakdown products (GBPs), especially isothiocyanates (ITCs) benefit human health. Chinese kale is a native Brassica vegetable in China, and its sprouts are rich in GSLs and nutritional substances. ITCs are the predominant GBPs while alternative products are formed in the presence of specifier proteins. However, fewer ITCs are formed in the sprouts. Epithiospecifier (ESP) promotes the formation of epithionitriles at the expense of ITCs in Arabidopsis, but a systematic study of different isoforms of ESPs in most vegetables is still missing. In this study, changes in the content of GBPs and the precursor GSLs, as well as thiols per plant were monitored during sprout development. The proportions of epithionitriles and ITCs in total GBPs were found to be increased and decreased, respectively. RNA-seq showed enhanced expression of numerous genes involved in GSLs biosynthesis and degradation, as well as sulfur assimilation in sprouts compared to seeds. Four copies of BoESPs were isolated and BoESP2 was the most abundant isoform. Generally, transcription of BoESPs showed a strong response to abscisic acid and gibberellin, and consequently epithionitriles increased under these treatments. Knockdown of BoESP2 expression through virus-induced gene silencing system could effectively increase total ITCs and decrease total epithionitriles. Overall, dynamic GSL metabolic flux exists in the sprouting period, and the expression of BoESPs determines the pattern of GBPs, suggesting that improving the health-promoting ITCs in Chinese kale sprouts through manipulating BoESPs by metabolic engineering is feasible.

Brassica oleracea is an agronomically important species of the Brassicaceae family, including several nutrient-rich vegetables grown and consumed across the continents. But its sustainability is heavily constrained by a range of destructive pathogens, among which, clubroot disease, caused by a biotrophic protist Plasmodiophora brassicae, has caused significant yield and economic losses worldwide, thereby threatening global food security. To counter the pathogen attack, it demands a better understanding of the complex phenomenon of Brassica-P. brassicae pathosystem at the physiological, biochemical, molecular, and cellular levels. In recent years, multiple omics technologies with high-throughput techniques have emerged as successful in elucidating the responses to biotic and abiotic stresses. In Brassica spp., omics technologies such as genomics, transcriptomics, ncRNAomics, proteomics, and metabolomics are well documented, allowing us to gain insights into the dynamic changes that transpired during host-pathogen interactions at a deeper level. So, it is critical that we must review the recent advances in omics approaches and discuss how the current knowledge in multi-omics technologies has been able to breed high-quality clubroot-resistant B. oleracea. This review highlights the recent advances made in utilizing various omics approaches to understand the host resistance mechanisms adopted by Brassica crops in response to the P. brassicae attack. Finally, we have discussed the bottlenecks and the way forward to overcome the persisting knowledge gaps in delivering solutions to breed clubroot-resistant Brassica crops in a holistic, targeted, and precise way.

Some broccoli (Brassica oleracea L. italic) accessions have purple sepals and cold weather would deepen the purple color, while the sepals of other broccoli lines are always green even in cold winter. The related locus or gene is still unknown. In this study, a high-density genetic map was constructed based on specific locus amplified fragment (SLAF) sequencing in a doubled-haploid segregation population with 127 individuals. And mapping of the purple sepal trait in flower heads based on phenotypic data collected during three seasons was performed. A genetic map was constructed, which contained 6694 SLAF markers with an average sequencing depth of 81.37-fold in the maternal line, 84-fold in the paternal line, and 15.76-fold in each individual population studied. In all of the annual data recorded, three quantitative trait loci (QTLs) were identified that were all distributed within the linkage group (LG) 1. Among them, a major locus, qPH.C01–2, located at 36.393 cM LG1, was consistently detected in all analysis. Besides this locus, another two minor loci, qPH.C01–4 and qPH.C01–5, were identified near qPH.C01–2, based on the phenotypic data from spring of 2018. The purple sepal trait could be controlled by a major single locus and two minor loci. The genetic map and location of the purple sepal trait of flower heads provide an important foundation for mapping other compound traits and the identification of the genes related to purple sepal trait in broccoli.

Background: Curd architecture is one of the most important characters determining the curd morphology of cauliflower. However, the genetic mechanism dissection of this complex trait at molecular level is lacking. Genes/QTLs responsible for the morphological differences between present-day loose-curd and compact-curd cauliflower haven’t been well revealed.Results: Herein, by using a common compact-curd parent and two loose-curd parents, we developed two double haploid (DH) populations including 122 and 79 lines, respectively. For each population, we decomposed the curd architecture concept into four parameters (basal diameter, stalk length, stalk angle and curd solidity), and collected corresponding phenotypic data for each parameter across two environments. The Kosambi function and composite interval mapping algorithm were conducted to construct the linkage map and analyze the QTLs associated with curd architecture parameters. A total of 20 QTLs were detected with the minimum likelihood of odd (LOD) values ranging from 2.61 to 8.38 and the percentage of the phenotypic variance explained by each QTL (PVE) varying between 7.69 and 25.10%. Of these, two QTLs controlling stalk length (qSL.C6–1, qSL.C6–2) and two QTLs controlling curd solidity (qCS.C6–1 and qCS.C6–2) were steadily expressed in both environments. Further, qSL.C6–1, qSL.C6–2, qCS.C6–1 and qCS.C6–4 fell into the same chromosomal region of the reference genome, indicating that these loci are involved in pleiotropic effects or are tightly linked.Conclusion: The current study identified a series of QTLs associated with curd architecture parameters, which might contribute essentially to the formation of present-day loose-curd cauliflower that is widely cultivated in China. These results may pave the way for intensive deciphering the molecular mechanisms of curd development and for marker-assisted selection of curd morphology in cauliflower breeding.