The SWEET (sugars will eventually be exported transporter) family was identified as a new class of sugar transporters that function as bidirectional uniporters/facilitators and facilitate the diffusion of sugars across cell membranes along a concentration gradient. SWEETs are found widely in plants and play central roles in many biochemical processes, including the phloem loading of sugar for long-distance transport, pollen nutrition, nectar secretion, seed filling, fruit development, plant–pathogen interactions and responses to abiotic stress. This review focuses on advances of the plant SWEETs, including details about their discovery, characteristics of protein structure, evolution and physiological functions. In addition, we discuss the applications of SWEET in plant breeding. This review provides more in-depth and comprehensive information to help elucidate the molecular basis of the function of SWEETs in plants.

TIFY, a plant-specific gene family with the conserved motif TIF[F/Y]XG, plays important roles in various plant biological processes. Here, a total of 36 TIFY genes were identified in the Brassica oleracea genome and classified into JAZ (22 genes), TIFY (7 genes), ZML (5 genes), and PPD (2 genes) subfamilies based on their conserved motifs, which were distributed unevenly across nine chromosomes with different lengths (339–1077 bp) and exon numbers (1–8). Following phylogenetic analysis with A. thaliana and B. rapa TIFY proteins, ten clades were obtained. The expression of these TIFY genes was organ-specific, with thirteen JAZ genes and two PPD genes showing the highest expression in roots and leaves, respectively. More importantly, the JAZs showed divergent responses to various pathogen infections and different phytohormone treatments. Compared with the susceptible line, most JAZs were activated after Plasmodiophora brassicae infection, while there were both induced and inhibited JAZs after Fusarium oxysporum or Xanthomonas campestris infection in the resistance line, indicating their probably distinct roles in disease resistance or susceptibility. Further, the JAZs were all upregulated after MeJA treatment, but were mostly downregulated after SA/ET treatment. In summary, these results contribute to our understanding of the TIFY gene family, revealing that JAZs may play crucial and divergent roles in phytohormone crosstalk and plant defense.

Clubroot is a soil-borne disease in cabbage (Brassica oleracea L. var. capitata L.) caused by Plasmodiophora brassicae, which poses a great threat to cabbage production. However, clubroot resistance (CR) genes in Brassica rapa could be introduced into the cabbage via breeding to make it clubroot resistant. In this study, CR genes from B. rapa were introduced into the cabbage genome and the mechanism of gene introgression was explored. Two methods were used to create CR materials: (i) The fertility of CR Ogura CMS cabbage germplasms containing CRa was restored by using an Ogura CMS restorer. After cytoplasmic replacement and microspore culture, CRa-positive microspore individuals were obtained. (ii) Distant hybridization was performed between cabbage and B. rapa, which contained three CR genes (CRa, CRb, and Pb8.1). Finally, BC₂ individuals containing all three CR genes were obtained. Inoculation results showed that both CRa-positive microspore individuals and BC₂ individuals containing three CR genes were resistant to race 4 of P. brassicae. Sequencing results from CRa-positive microspore individuals with specific molecular markers and genome-wide association study (GWAS) showed penetration at the homologous position of the cabbage genome by a 3.42 Mb CRa containing a fragment from B. rapa; indicating homoeologous exchange (HE) as the theoretical basis for the introgression of CR resistance. The successful introduction of CR into the cabbage genome in the present study can provide useful clues for creating introgression lines within other species of interest.

Broccoli (Brassica oleracea L. var. italica) is one of the most important vegetable crops cultivated worldwide. The market demand for broccoli is still increasing due to its richness in vitamins, anthocyanins, mineral substances, fiber, secondary metabolites and other nutrients. The famous secondary metabolites, glucosinolates, sulforaphane and selenium have protective effects against cancer. Significant progress has been made in fine-mapping and cloning genes that are responsible for important traits; this progress provides a foundation for marker-assisted selection (MAS) in broccoli breeding. Genetic engineering by the well-developed Agrobacterium tumefaciens-mediated transformation in broccoli has contributed to the improvement of quality; postharvest life; glucosinolate and sulforaphane content; and resistance to insects, pathogens and abiotic stresses. Here, we review recent progress in the genetics and molecular breeding of broccoli. Future perspectives for improving broccoli are also briefly discussed.

Cabbage (Brassica oleracea var. capitata) is a vegetable rich in glucosinolates (GSLs) that have proven health benefits. To gain insights into the synthesis of GSLs in cabbage, we systematically analyzed GSLs biosynthetic genes (GBGs) in the entire cabbage genome. In total, 193 cabbage GBGs were identified, which were homologous to 106 GBGs in Arabidopsis thaliana. Most GBGs in cabbage have undergone negative selection. Many homologous GBGs in cabbage and Chinese cabbage differed in expression patterns indicating the unique functions of these homologous GBGs. Spraying five exogenous hormones significantly altered expression levels of GBGs in cabbage. For example, MeJA significantly upregulated side chain extension genes BoIPMILSU1-1 and BoBCAT-3-1, and the expression of core structure construction genes BoCYP83A1 and BoST5C-1, while ETH significantly repressed the expression of side chain extension genes such as BoIPMILSU1-1, BoCYP79B2-1, and BoMAMI-1, and some transcription factors, namely BoMYB28-1, BoMYB34-1, BoMYB76-1, BoCYP79B2-1, and BoMAMI-1. Phylogenetically, the CYP83 family and CYP79B and CYP79F subfamilies may only be involved in GSL synthesis in cruciferous plants. Our unprecedented identification and analysis of GBGs in cabbage at the genome-wide level lays a foundation for the regulation of GSLs synthesis through gene editing and overexpression.