关键词: 甜橙, 柑橘溃疡病, CsNBS-LRR, 水杨酸, PR基因

Abstract: The citrus CsNBS-LRR gene was cloned and analyzed for its expression profiles induced by citrus canker and phytohormones. The function was verified by over-expression in Wanjincheng（Citrus sinensis），and further analysis was carried out for the mechanisms. The results showed that the open reading frame of CsNBS-LRR was 3 633 bp，encoding 1 210 amino acids. It was down-regulated by Xanthomonas citri subsp. citri（Xcc）in the susceptible variety Wanjincheng，and up-regulated in the resistant variety Calamondin（Citrus madurensis）. In Calamondin，CsNBS-LRR was significantly up-regulated by salicylic acid（SA），while in Wanjincheng it was slightly increased. In the two varieties，CsNBS-LRR was not significantly induced by methyl jasmonate（MeJA）. Overexpression（OE）of CsNBS-LRR significantly results in significantly enhanced resistance to citrus bacterial canker（CBC）in the transgenic lines，as revealed by the disease severity which was 75%–88% of the wild type. The salicylicacid content in the transgenic plants and the transcription level of key genes in the salicylic acid biosynthesis were significantly increased. Transcriptional levels of key genes in salicylic acid signaling pathway are also enhanced and more sensitive to the Xcc infection. Over all，CsNBS-LRR is a potential disease resistance gene of CBC，which can improve CBC resistance through the regulation of salicylic acid signaling pathway.

Key words: sweet orange, citrus bacterial canker（CBC）, CsNBS-LRR, salicylic acid, PR gene