Graduate School of Agricultural Science, Kobe University, Rokkodai, Nada-ku, Kobe, 657-8501, Japan.
Iwate Biotechnology Research Center, Narita, Kitakami, Iwate, 024-0003, Japan.
Plant Cell Rep. 2017 Dec;36(12):1841-1854. doi: 10.1007/s00299-017-2198-9. Epub 2017 Aug 17.
Resistant and susceptible lines in Brassica rapa have different immune responses against Fusarium oxysporum inoculation. Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans (Foc) is an important disease of Brassicaceae; however, the mechanism of how host plants respond to Foc is still unknown. By comparing with and without Foc inoculation in both resistant and susceptible lines of Chinese cabbage (Brassica rapa var. pekinensis), we identified differentially expressed genes (DEGs) between the bulked inoculated (6, 12, 24, and 72 h after inoculation (HAI)) and non-inoculated samples. Most of the DEGs were up-regulated by Foc inoculation. Quantitative real-time RT-PCR showed that most up-regulated genes increased their expression levels from 24 HAI. An independent transcriptome analysis at 24 and 72 HAI was performed in resistant and susceptible lines. GO analysis using up-regulated genes at 24 HAI indicated that Foc inoculation activated systemic acquired resistance (SAR) in resistant lines and tryptophan biosynthetic process and responses to chitin and ethylene in susceptible lines. By contrast, GO analysis using up-regulated genes at 72 HAI showed the overrepresentation of some categories for the defense response in susceptible lines but not in the resistant lines. We also compared DEGs between B. rapa and Arabidopsis thaliana after F. oxysporum inoculation at the same time point, and identified genes related to defense response that were up-regulated in the resistant lines of Chinese cabbage and A. thaliana. Particular genes that changed expression levels overlapped between the two species, suggesting that they are candidates for genes involved in the resistance mechanisms against F. oxysporum.
白菜抗感品种接种尖孢镰刀菌后表现出不同的免疫反应。由尖孢镰刀菌融合群（Fusarium oxysporum f. sp. conglutinans，Foc）引起的黄萎病是十字花科植物的一种重要病害；然而，寄主植物如何响应 Foc 的机制尚不清楚。通过比较白菜抗感品种接种和未接种尖孢镰刀菌（接种后 6、12、24 和 72 小时（HAI））的 bulked 样本，我们鉴定了差异表达基因（DEGs）。大多数 DEGs 被 Foc 接种上调。实时定量 RT-PCR 显示，大多数上调基因的表达水平从 24 HAI 开始增加。在抗感品种中，我们还分别在 24 和 72 HAI 进行了独立的转录组分析。使用 24 HAI 上调基因进行的 GO 分析表明，Foc 接种激活了抗性品种的系统性获得抗性（SAR），而在感病品种中激活了色氨酸生物合成过程和对几丁质和乙烯的反应。相比之下，使用 72 HAI 上调基因进行的 GO 分析显示，在感病品种中，防御反应的一些类别过度表达，但在抗性品种中没有。我们还比较了尖孢镰刀菌接种后同一时间点的白菜和拟南芥的 DEGs，并鉴定了在白菜抗性品种和拟南芥中上调的与防御反应相关的基因。两个物种之间表达水平变化的特定基因重叠，表明它们是参与抗尖孢镰刀菌机制的候选基因。
