The domestication of Brassica oleracea has resulted in diverse morphological types with distinct patterns of organ development. Here we report a graph-based pan-genome of B. oleracea constructed from high-quality genome assemblies of different morphotypes. The pan-genome harbors over 200 structural variant hotspot regions enriched in auxin- and flowering-related genes. Population genomic analyses revealed that early domestication of B. oleracea focused on leaf or stem development. Gene flows resulting from agricultural practices and variety improvement were detected among different morphotypes. Selective-sweep and pan-genome analyses identified an auxin-responsive small auxin up-regulated RNA gene and a CLAVATA3/ESR-RELATED family gene as crucial players in leaf-stem differentiation during the early stage of B. oleracea domestication and the BoKAN1 gene as instrumental in shaping the leafy heads of cabbage and Brussels sprouts. Our pan-genome and functional analyses further revealed that variations in the BoFLC2 gene play key roles in the divergence of vernalization and flowering characteristics among different morphotypes, and variations in the first intron of BoFLC3 are involved in fine-tuning the flowering process in cauliflower. This study provides a comprehensive understanding of the pan-genome of B. oleracea and sheds light on the domestication and differential organ development of this globally important crop species.

Anthocyanins perform diverse biological functions in plants and are beneficial to human health. Leaf color is the most important trait of ornamental kale and the characteristics of changes in leaf color make it an ideal material to elucidate genetic mechanisms of anthocyanins accumulation in Brassica oleracea. To elucidate the anthocyanin distribution, metabolic profiles and differentially expressed anthocyanin biosynthetic genes between different colored accessions can pave the way for understanding the genetic regulatory mechanisms of anthocyanin biosynthesis and accumulation in ornamental kale. In this study, anthocyanin distributions in red- and white-leaved ornamental kale accessions were determined. Thirty-four anthocyanins were detected in the red-leaved accession. The complete set of anthocyanin biosynthetic genes in the B. oleracea reference genome was identified and differential expression analysis based on RNA-seq was conducted. Eighty-one anthocyanin biosynthetic genes were identified in the B. oleracea reference genome. The expression patterns and differential expressions of these genes in different leaf types indicated that late biosynthetic genes (BoDFR1, BoANS1 and 2, and BoUGT79B1.1), positive regulatory genes (BoTTG1, BoTT8, and Bol012528), a negative regulatory gene (BoMYBL2.1), and transport genes (BoTT19.1 and BoTT19.2) may play roles in anthocyanin accumulation in ornamental kale. A genetic regulatory network of anthocyanin accumulation in ornamental kale was constructed. The distribution of pigments and anthocyanin profiles explained the leaf color phenotypes of ornamental kales. The identification of key genes and construction of genetic regulatory network in anthocyanin accumulation in ornamental kale elucidated the genetic basis of leaf color variants. These findings enhance the understanding of the genetic mechanisms and regulatory network of anthocyanin accumulation in B. oleracea, and provide a theoretical basis for breeding new cultivars of Brassica vegetables with enhanced ornamental and nutritional value.

The RNA-binding glycine-rich proteins (RBGs) of the glycine-rich protein family play vital roles in regulating gene expression both at the transcriptional and post-transcriptional levels. However, the members and functions in response to abiotic stresses of the RBG gene family remain unclear in Brassica oleracea. In this study, a total of 19 BoiRBG genes were identified through genome-wide analysis in broccoli. The characteristics of BoiRBG sequences and their evolution were examined. An analysis of synteny indicated that the expansion of the BoiRBG gene family was primarily driven by whole-genome duplication and tandem duplication events. The BoiRBG expression patterns revealed that these genes are involved in reaction to diverse abiotic stress conditions (i.e., simulated drought, salinity, heat, cold, and abscisic acid) and different organs. In the present research, the up-regulation of BoiRBGA13 expression was observed when subjected to both NaCl-induced and cold stress conditions in broccoli. Moreover, the overexpression of BoiRBGA13 resulted in a noteworthy reduction in taproot lengths under NaCl stress, as well as the inhibition of seed germination under cold stress in broccoli, indicating that RBGs play different roles under various stresses. This study provides insights into the evolution and functions of BoiRBG genes in Brassica oleracea and other Brassicaceae family plants.

The Bax inhibitor-1 (BI-1) gene family, which is important for plant growth, development, and stress tolerance, remains largely unexplored in cauliflower. In this study, we identified and characterized cauliflower BI-1 family genes. Based on aligned homologous sequences and collinearity with Arabidopsis genes, we identified nine cauliflower BI-1 genes, which encode proteins that varied in length, molecular weight, isoelectric point, and predicted subcellular localization, including the Golgi apparatus, plasma membrane, and various compartments within the chloroplast. Phylogenetic analyses detected evolutionary conservation and divergence among these genes. Ten structural motifs were identified, with Motif 5 found to be crucial for inhibiting apoptosis. According to the cis-regulatory elements in their promoters, these genes likely influence hormone signaling and stress responses. Expression profiles among tissues highlighted the functional diversity of these genes, with particularly high expression levels observed in the silique and root. Focusing on BobBIL4, we investigated its role in brassinosteroid (BR)-mediated root development and salt stress tolerance. BobBIL4 expression levels increased in response to BR and salt treatments. The functional characterization of this gene in Arabidopsis revealed that it enhances root growth and salinity tolerance. These findings provide insights into BI-1 gene functions in cauliflower while also highlighting the potential utility of BobBIL4 for improving crop stress resistance.