Chitosan Nanoparticles Encapsulate Antimicrobial Peptides for the Prevention and Control of Citrus reticulata Huanglongbing and Their Distribution in Plants

Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas), is a serious Bacterial disease affecting citrus. This study found that the expression of long stable antimicrobial peptide (LSAMP) increases with citrus immune genes CsPR1, CsPR2, and CsNPR1, indicating a link to citrus immunity. Additionally, cut antimicrobial peptide (CAMP) functions similarly to stable antimicrobial peptide (SAMP) in inhibiting CLas proliferation and boosting immunity in periwinkle (Catharanthus roseus). Chitosan nanoparticles (CS-NPs) were synthesized to encapsulate CAMP (CAMP-NPs) and SAMP (SAMP-NPs), which improved their stability and bioavailability. Both CAMP-NPs and SAMP-NPs outperformed their unencapsulated forms in inhibiting CLas proliferation and enhancing immunity in HLB-infected periwinkle and citrus; they also enhance citrus photosynthesis. Confocal microscopy revealed that CS-NPs mainly localized in the leaf apoplast but also penetrated chloroplasts. This study offers a novel biological control strategy for HLB and provides a practical framework for utilizing CS-NPs loaded with antimicrobial peptides (AMPs) for plant disease resistance.

chitosan nanoparticles; citrus huanglongbing; cut antimicrobial peptides.