金柑FcRGA1抗溃疡病机制初探

Preliminary Study on Mechanisms of Resistance to Citrus Canker of Kumquat FcRGA1

NBS-LRR类抗病蛋白是植物中最丰富的一类R蛋白成员,该家族含有典型的NB-ARC结构域与LRR结构域,主要参与植物抵御病原物入侵的防御过程。从金柑(Fortunella crassifolia)中克隆了1个含有NB-ARC结构域的R基因,命名为FcRGA1。该基因含有3954 bp的完整开放阅读框,编码1317个氨基酸。qRT-PCR分析表明,FcRGA1在金柑的根、茎、叶中均有表达,叶片中最高,根中最低。溃疡病菌侵染可促进FcRGA1表达上调,接种后12 h表达量为对照的12.3倍。通过VIGS技术沉默金柑叶片FcRGA1后,溃疡病菌侵染的叶片失绿更为严重,病斑面积更大,菌落数与相对电导率显著增加,同时叶绿素含量与过氧化氢含量显著低于对照,表明FcRGA1可能通过对活性氧的调控影响金柑对溃疡病的抗性。

NBS-LRR resistant proteins are the most abundant R protein members in plants.This family contains typical NB-ARC domains and LRR domains,which are mainly involved in the defense process of plants against pathogen’s invasion.In this study,an R gene containing the NB-ARC domain was cloned from kumquat(Fortunella crassifolia)and named FcRGA1.This gene contained a complete open reading frame(ORF)of 3954 bp and encoded 1317 amino acids.qRT-PCR analysis showed that the FcRGA1 gene was expressed in the roots,stems and leaves of kumquat,with the highest expression level in the leaves and the lowest in the roots.Furthermore,the expression of FcRGA1 gene was up-regulated by infection with canker bacteria and reached the highest value at 12 h,which was 12.3 times higher than that of the control.After silencing the FcRGA1 gene by VIGS(Virus-induced Gene Silencing),kumquat leaves in the silenced group showed more severe chlorosis symptom than those in control group after inoculated by Xcc(Xanthomonas citri subsp.citri),concurrent with significantly higher lesion area,bacterial growth and relative electrolytic leakage.Whereas,the chlorophyll content and hydrogen peroxide content were significantly lower in comparison with the control group,indicating that FcRGA1 might affect the resistance of kumquat to citrus canker through the regulation of reactive oxygen species.