Identifying the role of cellulase gene CsCEL20 upon the infection of Xanthomonas citri subsp. citri in citrus

Yi Li; Huijie Lou; Hongyan Fu; Hanying Su; Chenxing Hao; Jianming Luo; Nan Cai; Yan Jin; Jian Han; Ziniu Deng; Yunlin Cao; Xianfeng Ma

doi:10.1007/s11032-024-01531-3

Identifying the role of cellulase gene CsCEL20 upon the infection of Xanthomonas citri subsp. citri in citrus

Mol Breed. 2025 Jan 6;45(1):10. doi: 10.1007/s11032-024-01531-3. eCollection 2025 Jan.

Authors

Yi Li^{1

2}, Huijie Lou^{1

2}, Hongyan Fu³, Hanying Su^{1

2}, Chenxing Hao^{1

2}, Jianming Luo^{1

2}, Nan Cai^{1

2}, Yan Jin^{1

2}, Jian Han³, Ziniu Deng^{1

2

4}, Yunlin Cao^{1

2}, Xianfeng Ma^{1

2}

Affiliations

¹ Engineering Research Center of Education Ministry for Germplasm Innovation and Breeding New Varieties of Horticultural Crops, College of Horticulture, Hunan Agricultural University, Changsha, 410128 China.
² National Center for Citrus Improvement-Changsha, College of Horticulture, Hunan Agricultural University, Changsha, 410128 China.
³ Hunan Horticultural Research Institute, Hunan Academy of Agricultural Sciences, Changsha, 410125 China.
⁴ Nanling Institute of Citrus Industry, Chenzhou, 423000 China.

PMID: 39781329
PMCID: PMC11704107 (available on 2026-01-06)
DOI: 10.1007/s11032-024-01531-3

Abstract

Citrus canker is a devastating disease caused by Xanthomonas citri subsp. citri (Xcc), which secretes the effector PthA4 into host plants to trigger transcription of the susceptibility gene CsLOB1, resulting in pustule formation. However, the molecular mechanism underlying CsLOB1-mediated susceptibility to Xcc remains elusive. This study identified CsCEL20 as a target gene positively regulated by CsLOB1. Cell expansion and cell wall degradation were observed in sweet orange leaves after Xcc infection. A total of 69 cellulase genes were retrieved within the Citrus sinensis genome, comprising 40 endoglucanase genes and 29 glucosidase genes. Transcriptomic analysis revealed that expression levels of CsCEL8, CsCEL9, CsCEL20, and CsCEL26 were induced by Xcc invasion in sweet orange leaves, but not in the resistant genotype Citron C-05. Among them, CsCEL20 exhibited the highest expression level, with an over 430-fold increase following Xcc infection. Additionally, RT-qPCR analysis confirmed that CsCEL20 expression was induced in susceptible genotypes (Sweet orange, Danna citron, Lemon) upon Xcc invasion, but not in resistant genotypes (Citron C-05, Aiguo citron, American citron). A Single-Nucleotide Polymorphism (SNP) at -423 bp was identified in the CEL20 promoters and exhibits a difference between eight susceptible citrus genotypes and three resistant ones. Moreover, CsCEL20 expression was upregulated in CsLOB1-overexpression transgenic lines compared to the wild type. Dual-luciferase reporter assays indicated that CsLOB1 can target the -505 bp to -168 bp region of CsCEL20 promoter to trans-activate its expression. These findings suggest that CsCEL20 may function as a candidate gene for citrus canker development and may be a promising target for biotechnological breeding of Xcc-resistant citrus genotypes.

Supplementary information: The online version contains supplementary material available at 10.1007/s11032-024-01531-3.

Keywords: Cellulase; Citrus Canker; CsCEL20; CsLOB1; Endoglucanase.

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