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. 2025 Jul 30;26(15):7359.
doi: 10.3390/ijms26157359.

Transcriptomic Reprogramming and Key Molecular Pathways Underlying Huanglongbing Tolerance and Susceptibility in Six Citrus Cultivars

Xiaohong Chen  1 , Fang Fang  1 , Tingting Chen  1 , Jinghua Wu  1 , Zheng Zheng  1 , Xiaoling Deng  1
Affiliations

Transcriptomic Reprogramming and Key Molecular Pathways Underlying Huanglongbing Tolerance and Susceptibility in Six Citrus Cultivars

Xiaohong Chen et al. Int J Mol Sci. .

Abstract

Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), is the most devastating disease threatening global citrus production. Although no commercial citrus varieties exhibit complete HLB resistance, genotype-specific tolerance variations remain underexplored. This study conducted a comparative transcriptomic profiling of six commercially citrus cultivars in South China, four susceptible cultivars (C. reticulata cv. Tankan, Gongkan, Shatangju, and C. sinensis Osbeck cv. Newhall), and two tolerant cultivars (C. limon cv. Eureka; C. maxima cv Guanxi Yu) to dissect molecular mechanisms underlying HLB responses. Comparative transcriptomic analyses revealed extensive transcriptional reprogramming, with tolerant cultivars exhibiting fewer differentially expressed genes (DEGs) and targeted defense activation compared to susceptible genotypes. The key findings highlighted the genotype-specific regulation of starch metabolism, where β-amylase 3 (BAM3) was uniquely upregulated in tolerant varieties, potentially mitigating starch accumulation. Immune signaling diverged significantly: tolerant cultivars activated pattern-triggered immunity (PTI) via receptor-like kinases (FLS2) and suppressed ROS-associated RBOH genes, while susceptible genotypes showed the hyperactivation of ethylene signaling and oxidative stress pathways. Cell wall remodeling in susceptible cultivars involved upregulated xyloglucan endotransglucosylases (XTH), contrasting with pectin methylesterase induction in tolerant Eureka lemon for structural reinforcement. Phytohormonal dynamics revealed SA-mediated defense and NPR3/4 suppression in Eureka lemon, whereas susceptible cultivars prioritized ethylene/JA pathways. These findings delineate genotype-specific strategies in citrus-CLas interactions, identifying BAM3, FLS2, and cell wall modifiers as critical targets for breeding HLB-resistant cultivars through molecular-assisted selection. This study provides a foundational framework for understanding host-pathogen dynamics and advancing citrus immunity engineering.

Keywords: citrus cultivar; host response; huanglongbing; susceptible; tolerant.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Representative leaf phenotypes and CLas quantification in six citrus cultivars. CLas titers measured by qPCR in leaves (mean ± SD, n = 3).
Figure 2
Figure 2
Statistical plot of differentially expressed genes (DEGs) in six citrus varieties in response to Candidatus Liberibacter asiaticus infection.
Figure 3
Figure 3
Venn diagram of differentially expressed genes (DEGs) in six varieties in response to Candidatus Liberibacter asiaticus infection.
Figure 4
Figure 4
Heatmaps of differentially expressed genes (DEGs) involved in starch and sucrose metabolism, secondary metabolism, and transcription factors.
Figure 5
Figure 5
Heatmaps of differentially expressed genes (DEGs) involved in innate immune signaling, phytohormone metabolism, and cell wall metabolism.
See this image and copyright information in PMC

References

    1. Bové J.M. Huanglongbing: A destructive, newly-emerging, century-old disease of citrus. J. Plant Pathol. 2006;88:7–37.
    1. Zheng Z., Chen J.C., Deng X.L. Historical perspectives, management, and current research of citrus HLB in Guangdong Province of China, where the disease has been endemic for over a hundred years. Phytopathology. 2018;108:1224–1236. doi: 10.1094/PHYTO-07-18-0255-IA. - DOI - PubMed
    1. Jagoueix S., Bové J.M., Garnier M. The phloem-limited bacterium of greening disease of citrus is a member of the α subdivision of the Proteobacteria. Int. J. Syst. Evol. Microbiol. 1994;44:379–386. doi: 10.1099/00207713-44-3-379. - DOI - PubMed
    1. Teixeira D.D.C., Saillard C., Eveillard S., Danet J.L., Costa P.I.D., Ayres A.J., Bové J.M. ‘Candidatus Liberibacter americanus’, associated with citrus huanglongbing (greening disease) in São Paulo State, Brazil. Int. J. Syst. Evol. Microbiol. 2005;55:1857–1862. doi: 10.1099/ijs.0.63677-0. - DOI - PubMed
    1. Folimonova S.Y., Robertson C.J., Garnsey S.M., Gowda S., Dawson W.O. Examination of the responses of different genotypes of citrus to huanglongbing (citrus greening) under different conditions. Phytopathology. 2009;99:1346–1354. doi: 10.1094/PHYTO-99-12-1346. - DOI - PubMed

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