甘蓝型油菜异分支酸合酶基因的克隆及信号通路相关基因的诱导表达

BnICS1 induced expression and related signaling pathway from Brassica napus

为了解异分支酸合酶1(ICS1,水杨酸合成的限速酶)在甘蓝型油菜抗病过程中的功能,以甘蓝型油菜耐菌核病品种宁RS-1为材料,在核盘菌侵染时,研究甘蓝型油菜ICS1基因和水杨酸信号通路相关基因的诱导表达。首先利用同源序列法克隆得到宁RS-1中ICS1基因的c DNA序列,命名为Bn ICS1。Bn ICS1序列全长1 719bp,编码572个氨基酸残基,含有1个分支酸结合域。表明油菜中也存在异分支酸途径。接种核盘菌前、后及不同时期荧光实时定量PCR结果发现Bn ICS1在核盘菌接种后6hpi(接种后6h)表达量升高,但是24hpi后降低;而MPK4基因的表达量在6hpi降低,24hpi后升高,说明SA合成先是被核盘菌诱导,但随后又被抑制。EDS5基因和PR1基因表达量从接种后6hpi持续升高,而PDF1.2基因的表达量不断降低,说明SA信号通路最终受核盘菌诱导形成病斑,而茉莉酸途径及其诱导的植物防御反应受到抑制。

Key enzyme of SA（ salicylic acid） synthesis is isochorismate synthase 1（ ICS1）. To better understand the function of this enzyme gene in Brassica napus against infection by Sclerotinia sclerotiorum,c DNA of Bn ICS1 was cloned based on homologous sequence in B. rapa. The complete open reading frame of Bn ICS1 is 1 719 bp long,encoding 572 amino acids with a predictd chorismate- bind domain. Real- time RT- PCR showed that Bn ICS1 expression increased at 6 hpi（ hours post- inoculation）,but decreased after 24 hpi. SA signaling pathway genes were induced. MPK4 expression decreased at 6 hpi,but increased after 24 hpi. These revealed that SA synthesis was induced by S. sclerotiorum at the beginning,but suppressed after necrotic lesions appeared. Expressions of EDS5 and PR1 were increased from 6 hpi,and PDF1. 2 was decreased after inoculation. Results indicated that SA signaling pathway eventually led to necrotic lesions,while jasmonic acid pathway was inhibited.