| Summary: | Huanglongbing (HLB), a bacterial disease caused by <i>Candidatus</i> Liberibacter asiaticus (<i>C</i>Las), is a major threat to the citrus industry. In a previous study conducted by our laboratory, several citrus transgenic trees expressing the <i>Arabidopsis thaliana NPR1</i> (<i>AtNPR1</i>) gene remained HLB-free when grown in a field site under high HLB disease pressure. To determine the molecular mechanisms behind <i>AtNPR1-</i>mediated tolerance to HLB, a transcriptome analysis was performed using <i>AtNPR1</i> overexpressing transgenic trees and non-transgenic trees as control, from which we identified 57 differentially expressed genes (DEGs). Data mining revealed the enhanced transcription of genes encoding pathogen-associated molecular patterns (PAMPs), transcription factors, leucine-rich repeat receptor kinases (LRR-RKs), and putative ankyrin repeat-containing proteins. These proteins were highly upregulated in the <i>AtNPR1</i> transgenic line compared to the control plant. Furthermore, analysis of protein−protein interactions indicated that AtNPR1 interacts with CsNPR3 and CsTGA5 in the nucleus. Our results suggest that <i>AtNPR1</i> positively regulates the innate defense mechanisms in citrus thereby boosting resistance and effectively protecting the plant against HLB.
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