Acta Horticulturae Sinica ›› 2022, Vol. 49 ›› Issue (7): 1441-1457.doi: 10.16420/j.issn.0513-353x.2021-0553

• Research Papers • Previous Articles     Next Articles

Gene Cloning and Expression Analysis of NAC Gene in Citrus in Response to Huanglongbing

ZHENG Lin, WANG Shuai, LIU Yunuo, DU Meixia, PENG Aihong, HE Yongrui, CHEN Shanchun(), ZOU Xiuping()   

  1. Citrus Research Institute,Southwest University/Chinese Academy of Agricultural Sciences,Chongqing 400712,China
  • Received:2022-02-08 Revised:2022-04-25 Online:2022-07-25 Published:2022-07-29
  • Contact: CHEN Shanchun,ZOU Xiuping;


Citrus Huanglongbing(HLB)has become a major disease and limiting factor of production in citrus areas that have become infected. It can cause production extinction when the damage to citrus industry is serious,and there is no effective prevention and treatment method for this disease. The key to solve this problem is to excavate citrus resistance genes for disease resistance breeding. Therefor,in this study,based on the transcriptome data of Candidatus Liberibacter asiaticus(CLas)in the root and midrib in the early stage of infection(2 months),nine NAC(NAM,ATAF1/2,CUC2)genes were screened in response to HLB infection,and three genes with high differential expression were cloned,named as CsNAC21/22,CsNAC68 and CsNAC78,respectively. Bioinformatics analysis showed that CsNAC21/22,CsNAC68 and CsNAC78 encoded 306,503 and 152 amino acids respectively,and the isoelectric point(pI) was 5.43,6.59 and 8.39,respectively. The conserved domain analysis showed that CsNAC21/22,CsNAC68 and CsNAC78 contained five subdomains of the conserved domain A-E,and the A,C and D parts were relatively conserved,which was consistent with the characteristics of the NAC gene family. Phylogenetic tree analysis showed that CsNAC21/22 was closely related to Glycine max and Populus trichocarpa,and CsNAC68 and CsNAC78 were closely related to Arabidopsis thaliana and Populus trichocarpa. Subcellular localization analysis showed that CsNAC68 located in the nucleus,and CsNAC21/22 and CsNAC78 located in the nucleus and cytoplasm. Real-time fluorescent quantitative PCR(qRT-PCR)analysis showed that the three candidate genes showed significantly different tissue and pathogen induced expression characteristics in HLB susceptible Jincheng(Citrus sinensis)and HLB resistant Mafenggan(C. hystrix)and Jiulixiang(Murraya exotica). With healthy plants as the control,the expression levels of CsNAC68 and CsNAC78 were significantly up-regulated in the Jincheng root in response to CLas infection,while CsNAC68 was in response to CLas infection in the mesophyll of Jiulixiang and the root of Mafenggan significantly up-regulated expression. The expression of CsNAC21/22 was significantly down-regulated in the root of Jincheng and the mesophyll of Mafenggan. Using Jincheng leaves as the test material,the expression characteristics of candidate genes in response to plant hormone induction were analyzed by qRT-PCR. The results showed that the three genes may be involved in the signal transduction pathway of abscisic acid(ABA),and CsNAC68 may be involved in the signal transduction pathway of salicylic acid(SA)and jasmonic acid(JA),and CsNAC78 may be involved in the signal transduction pathway of ethylene(ETH).

Key words: Citrus, Huanglongbing, NAC, gene cloning, expression analysis

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