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.

Fusarium wilt of cabbage (Brassica oleracea var. capitata), caused by Fusarium oxysporum f. sp. conglutinans (Foc), poses a significant threat to global cabbage production. Although resistance screening and the initial cloning of resistance genes in cabbage have been previously reported, the specific molecular mechanisms underlying cabbage resistance to Foc remain largely unknown. To elucidate the underlying mechanisms, we performed RNA sequencing analysis on a near-isogenic resistant line YR01_20 and a susceptible NIL line S01_20 by comparing both Foc-inoculated and mock-inoculated conditions. A total of 508.6 million sequencing raw reads (76.8 Gb data volume) were generated across all samples. Bioinformatics analysis of differentially expressed genes (DEGs) between S01_20 and YR01_20 revealed significant enrichment in plant hormone signaling and mitogen-activated protein kinase (MAPK) pathways. Notably, BolC06g030650.2J, encoding the plant defensin protein PDF1.2, was significantly upregulated in both pathways. Real-time quantitative PCR (RT-qPCR) analysis confirmed that PDF1.2 was significantly upregulated in the resistant line at 12 h post-inoculation and remained elevated for up to 144 h. Furthermore, transgenic cabbage overexpressing PDF1.2 exhibited significantly enhanced resistance to Foc. Taken together, these findings advance our understanding of the molecular mechanisms governing cabbage resistance to Fusarium wilt and identify PDF1.2 as a genetic target for breeding Foc-resistant cabbage cultivars through molecular approaches.

Cabbage (Brassica oleracea var. capitata) Fusarium wilt (CFW) is a disease that poses a critical threat to global cabbage production. Screening for resistant resources in order to support the breeding of resistant cultivars is the most reliable approach to control this disease. CFW is caused by Fusarium oxysporum f. sp. conglutinans (Foc), which consists of two physiological races (race 1 and 2). While many studies have focused on resistance screening, gene mining, and inheritance-based research associated with resistance to Foc race 1, there have been few studies specifically analyzing resistance to Foc race 2, which is a potential threat that can overcome type A resistance. Here, 166 cabbage resources collected from around the world were evaluated for the resistance to both Foc races, with 46.99% and 38.55% of these cabbage lines being resistant to Foc race 1 and race 2, respectively, whereas 33.74% and 48.80% were susceptible to these two respective races. Of these 166 analyzed cabbage lines, 114 (68.67%) were found to be more susceptible to race 2 than to race 1, and 28 of them were resistant to race 1 while susceptible to race 2, underscoring the highly aggressive nature of Foc race 2. To analyze the inheritance of Foc race 2 resistance, segregated populations derived from the resistant parental line ‘Badger Inbred 16’ and the susceptible one ‘01-20’ were analyzed with a major gene plus polygene mixed genetic model. The results of this analysis revealed Foc race 2-specific resistance to be under the control of two pairs of additive-dominant-epistatic major genes plus multiple additive-dominant-epistatic genes (model E). The heritability of these major genes in the BC₁P₁, BC₁P₂, and F₂ generations were 32.14%, 72.80%, and 70.64%, respectively. In summary, these results may aid in future gene mining and breeding of novel CFW-resistant cabbage cultivars.