关键词: 柑橘, 信号肽, 抗菌肽, 柑橘溃疡病, 遗传转化, 抗性

Abstract: A Citrus canker caused by Xanthomonas axonopodis pv. citri（Xac）is a very destructive
disease，which affects the citrus industry in most citrus-producing areas of the world. Here，we reported the
production of transgenic Tarocco blood orange（C. sinensis Osbeck）containing the synthetic antibacterial
peptide genes and the evaluation of transgenic plants for resistance to Xac. Two new Cecropin B（CB）
antibacterial peptide genes PR1aCB and AATCB with signal peptide（SP）sequence were synthesized by PCR. Transient RFP expression showed that fluorescence accumulation was observed predominantly in
intercellular space surrounding the onion epidermal cells transformed with PR1aCB︰rfp and AATCB︰rfp
genes compared with CB︰rfp without SP，indicating the SPs could direct protein secretion to the apoplast.
PR1aCB and AATCB gene cassettes driven by CaMV 35S were introduced into Tarocco blood orange by
Agrobacterium-mediated transformation. Integration of transgenes into citrus genome was confirmed by
GUS histochemical staining，PCR and Southern blot. Transcriptions of PR1aCB and AATCB genes were
detected by Real-time quantitative PCR in transgenic plants. Transgenic leaves were in vitro inoculated
with suspension of Xac. Compared to control（nontrangenic plants and pGN transgenic plants without
antibacterial gene），ten transgenic lines showed significant increase in resistance to citrus canker. The
levels of the resistance of the transgenic lines were equivalent to that of the highly resistant varieties：
Nanfeng Miju（C. succosa Hort. Ex Tan）and Calamondin（C. madurensis）.

Key words: Citrus, signal peptide, antibacterial peptide, citrus canker, genetic transformation, resistance