Brassica oleracea has been developed into many important crops, including cabbage, kale, cauliflower, broccoli and so on. The genome and gene annotation of cabbage (cultivar JZS), a representative morphotype of B. oleracea, has been widely used as a common reference in biological research. Although its genome assembly has been updated twice, the current gene annotation still lacks information on untranslated regions (UTRs) and alternative splicing (AS). Here, we constructed a high-quality gene annotation (JZSv3) using a full-length transcriptome acquired by nanopore sequencing, yielding a total of 59452 genes and 75684 transcripts. Additionally, we re-analyzed the previously reported transcriptome data related to the development of different tissues and cold response using JZSv3 as a reference, and found that 3843 out of 11908 differentially expressed genes (DEGs) underwent AS during the development of different tissues and 309 out of 903 cold-related genes underwent AS in response to cold stress. Meanwhile, we also identified many AS genes, including BolLHCB5 and BolHSP70, that displayed distinct expression patterns within variant transcripts of the same gene, highlighting the importance of JZSv3 as a pivotal reference for AS analysis. Overall, JZSv3 provides a valuable resource for exploring gene function, especially for obtaining a deeper understanding of AS regulation mechanisms.

Non-heading Chinese cabbage, a variety of Brassica campestris, is an important vegetable crop in the Yangtze River Basin of China. However, the immaturity of its stable transformation system and its low transformation efficiency limit gene function research on non-heading Chinese cabbage. Agrobacterium rhizogenes-mediated (ARM) transgenic technology is a rapid and effective transformation method that has not yet been established for non-heading Chinese cabbage plants. Here, we optimized conventional ARM approaches (one-step and two-step transformation methods) suitable for living non-heading Chinese cabbage plants in nonsterile environments. Transgenic roots in composite non-heading Chinese cabbage plants were identified using phenotypic detection, fluorescence observation, and PCR analysis. The transformation efficiency of a two-step method on four five-day-old non-heading Chinese cabbage seedlings (Suzhouqing, Huangmeigui, Wuyueman, and Sijiu Caixin) was 43.33%–51.09%, whereas using the stout hypocotyl resulted in a transformation efficiency of 54.88% for the 30-day-old Sijiu Caixin. The one-step method outperformed the two-step method; the transformation efficiency of different varieties was above 60%, and both methods can be used to obtain transgenic roots for functional studies within one month. Finally, optimized ARM transformation methods can easily, quickly, and effectively produce composite non-heading Chinese cabbage plants with transgenic roots, providing a reliable foundation for gene function research and non-heading Chinese cabbage genetic improvement breeding.

Cytokinins are a class of phytohormones that promote cell division and differentiation and are thought to affect plant immunity to multiple pathogens. However, a comprehensive analysis of cytokinin dehydrogenase/oxidase (CKX) family genes in cabbage has not been reported. In this study, a total of 36 CKX genes were identified using a genome-wide search method. Phylogenetic analysis classified these genes into three groups. They were distributed unevenly across nine chromosomes in B. oleracea, and 15 of them did not contain any introns. The results of colinearity analysis showed that 36 CKX gene in Arabidopsis was present in several copies in the Brassica oleracea genome. An analysis of cis-acting elements indicated that all genes possessed at least one stress or hormone responsive cis-acting element. A heatmap of CKX gene expression showed the patterns of expression of these genes in various tissues and organs. Three genes (Bol028363, Bol031036 and Bol018140) were relatively highly expressed in all of the investigated tissues under normal conditions, showing the expression profile of housekeeping genes. Generally, the expression patterns of CKX genes in Jingfeng 1 and Xiangan 336 were quite different under the same treatment. Notably, three genes (Bol020547, Bol028392 and Bol045724) were significantly down-regulated and up-regulated in the susceptible and resistant material, respectively, after inoculation, which may indicate their crucial roles in resistance to clubroot disease. The results provide insights for better understanding the roles of CKX genes in the B. oleracea–P. brassicae interaction.