Transcriptome Analysis of Cabbage Near-Isogenic Lines Reveals the Involvement of the Plant Defensin Gene PDF1.2 in Fusarium Wilt Resistance

<i>Fusarium</i> wilt of cabbage (<i>Brassica oleracea</i> var. <i>capitata</i>), caused by <i>Fusarium oxysporum</i> f. sp. <i>conglutinans</i> (<i>Foc</i>), 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 <i>Foc</i> 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 <i>Foc</i>-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, <i>BolC06g030650.2J</i>, encoding the plant defensin protein PDF1.2, was significantly upregulated in both pathways. Real-time quantitative PCR (RT-qPCR) analysis confirmed that <i>PDF1.2</i> was significantly upregulated in the resistant line at 12 h post-inoculation and remained elevated for up to 144 h. Furthermore, transgenic cabbage overexpressing <i>PDF1.2</i> exhibited significantly enhanced resistance to <i>Foc</i>. Taken together, these findings advance our understanding of the molecular mechanisms governing cabbage resistance to <i>Fusarium</i> wilt and identify <i>PDF1.2</i> as a genetic target for breeding <i>Foc</i>-resistant cabbage cultivars through molecular approaches.