Abstract: Huanglongbing（HLB）often causes the loss and abnormal distribution of zinc（Zn）element in citrus plant. Zn，which is required for activity of alcohol dehydrogenases（ADH），plays important roles in regulation of ADH responding to biotic- and abiotic-stress. Our proteome sequencing showed that a citrus alcohol dehydrogenase 1（CsADH1）had significantly different expression in HLB-affected citrus compared with healthy control. Here，the 1 143 bp-long CDS sequence of CsADH1，which encodes a protein of 380 amino acid residues，was cloned from‘Wanjincheng’orange（Citrus sinensis Osbeck）. Informatic analysis showed that CsADH1 had the GroES and ADH_zinc_N functional domains. Sequence alignment showed that CsADH1 shared high amino acid identities with alcohol dehydrogenase（ADH）members from Arabidopsis，castor and lotus. Subcellular localization analysis showed that CsADH1 protein located in the cytoplasm of onion epidermic cells. Real-time quantitative analysis revealed that CsADH1 had up-regulated expression in root and midrib of‘Wanjincheng’orange after HLB pathogen infection and the expression level in root was 10 times higher than that in midrib. CsADH1 expression was also upregulated by Zn ion，salicylic acid（SA），auxin（IAA）and abscisic acid（ABA）induction and its expression levels in roots were obviously higher than that in leaves. The results suggested that CsADH1 play a more important role in the responses of citrus roots to HLB infection compared with midrib.

Key words: citrus, Huanglongbing（HLB）, gene expression, subcellular localization, qPCR, Zn ion, CsADH1