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Acta Horticulturae Sinica ›› 2024, Vol. 51 ›› Issue (9): 2168-2182.doi: 10.16420/j.issn.0513-353x.2023-0792

• Plant Protection • Previous Articles     Next Articles

Expression Characteristics and Function Analysis of CsMEKK1-1 Gene in Response to Huanglongbing in Citrus

DONG Liting, QU Rongrong, PANG Shuwei, MO Kaiqin, CHEN Shuang, SHANG Lanyue, ZOU Xiuping*()   

  1. Integrative Science Center of Germplasm Creation in Western China(Chongqing)Science City,Citrus Research Institute,Southwest University,Chongqing 400712,China
  • Received:2024-05-29 Revised:2024-08-08 Online:2024-09-25 Published:2024-09-19
  • Contact: ZOU Xiuping

Abstract:

It has been shown that MAPK(mitogen-activated protein kinase)signaling pathway plays a key role in regulating citrus Huanglongbing(HLB)disease,but the key genes and mechanisms involved in this pathway need to be elucidated. Comparative transcriptome analysis of the mesophyll and midrib tissues from‘Jincheng’oranges[Citrus sinensis (L.) Osbeck]at the early stage(four months)of“CandidatusLiberibacter asiaticus”(CLas)infection revealed that differentially expressed genes(DEGs) were significantly enriched in the MAPK signaling pathway. Among these DEGs,four MEKK1 genes involved in the first cascade of the MAPK signaling pathway were up-regulated in the mesophylls,but they had no differential expression in midribs. Real-time fluorescence quantitative PCR(qRT-PCR)analysis showed that the expression of four CsMEKK1 genes were significantly different in different tissues from the HLB-susceptible‘Jincheng’orange and the HLB-tolerant‘Mafenggan’orange(Citrus hystrix)during CLas infection. CsMEKK1-1 showing the most significantly differential expression was selected for further analysis. Bioinformatics analysis showed that CsMEKK1-1 belongs to the MEKK gene family. Tobacco subcellular localization showed that CsMEKK1-1 was localized in the cell cytoplasm,nucleus and chloroplast. Expression characteristics of CsMEKK1-1 gene in response to salicylic acid(SA),jasmonic acid(JA),abscisic acid(ABA),ethylene(ETH)and CLas-flg22 in healthy‘Jincheng’leaves were analyzed by qRT-PCR. The results showed that CsMEKK1-1 expression was downregulated by SA,JA and ETH and CLas-flg22 mainly down-regulated CsMEKK1-1 expression. To evaluate CsMEKK1-1 function,MEKK1-1 overexpression and RNA interference(RNAi)vectors were constructed,and were introduced into CLas-infected‘Jincheng’branches to generate transgenic hairy roots using Agrobacterium rhizogenes-mediated citrus transformation. Quantitative PCR analysis showed that CsMEKK1-1 positively promoted CLas proliferation in hairy roots,indicating that CsMEKK1-1 is a susceptible gene for HLB disease.

Key words: Citrus, Huanglongbing, MAPK signaling pathway, CsMEKK1-1, disease-susceptible gene