Li Xue, Zhou Yue, Chen Hang, Guo Zetian, Zhang Jinlian, Chen Wenli
MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, School of Optoelectronic Science and Engineering, South China Normal University, Guangzhou, 510631, China.
Microbiology Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, 530007, China.
Plant Cell Rep. 2025 Jan 26;44(2):38. doi: 10.1007/s00299-024-03397-3.
The three SDEs of CLas were expressed in citrus leaves by AuNPs-PEI mediated transient expression system, and promoted the proliferation of CLas and inhibited citrus immunity. Huanglongbing (HLB) is the most severe bacterial disease of citrus caused by Candidatus Liberibacter asiaticus (CLas). CLas suppress host immune responses and promote infection by sec-dependent effectors (SDEs), thus insight into HLB pathogenesis is urgently needed to develop effective management strategies. In this study, we focused on the roles of SDE4310, SDE4435 and SDE4955 in citrus. We found that the expression of SDE4310, SDE4435 and SDE4955 to increase with increasing citrus immune genes CsPR1, CsPR2, CsPR5, CsNPR1, CsRBOHD, CsMAP3K and CsBIK1, suggesting that the level of citrus immunity could be judged by the expression of SDE. To further explore the relationship between these three SDEs and citrus immunity, we established a transient expression system in citrus leaves, using gold nanoparticle-polyethyleneimine (AuNPs-PEI) to deliver recombinant plasmid containing SDE4310, SDE4435 or SDE4955 respectively into citrus leaves. Results showed that SDE4310, SDE4435 and SDE4955 were successfully expressed in citrus leaves using this transient expression system, and found that SDE4310, SDE4435 and SDE4955 could promote the CLas proliferation by decreasing the immune gene expression of the citrus. Additionally, we used AuNPs-PEI to deliver siRNA to citrus cells, significantly reducing the expression of SDE4310 within 3 days. Although the suppression of SDE4310 expression did not inhibit the CLas proliferation, it increased the expression level of CsPR1, CsNPR1 and CsBIK1. This is also the first time that AuNPs-PEI has been found to be able to deliver exogenous plasmids into citrus cells and express the target protein, providing a new method for future studies on citrus HLB.
柑橘黄龙病菌（CLas）的三个依赖Sec的效应子（SDEs）通过金纳米粒子-聚乙烯亚胺（AuNPs-PEI）介导的瞬时表达系统在柑橘叶片中表达，促进了CLas的增殖并抑制了柑橘的免疫反应。黄龙病（HLB）是由亚洲韧皮杆菌（Ca. Liberibacter asiaticus，CLas）引起的最严重的柑橘细菌性病害。CLas通过依赖Sec的效应子抑制宿主免疫反应并促进感染，因此迫切需要深入了解HLB的发病机制以制定有效的管理策略。在本研究中，我们聚焦于SDE4310、SDE4435和SDE4955在柑橘中的作用。我们发现SDE4310、SDE4435和SDE4955的表达随着柑橘免疫基因CsPR1、CsPR2、CsPR5、CsNPR1、CsRBOHD、CsMAP3K和CsBIK1表达的增加而增加，这表明柑橘免疫水平可以通过SDE的表达来判断。为了进一步探究这三个SDE与柑橘免疫之间的关系，我们在柑橘叶片中建立了一个瞬时表达系统，利用金纳米粒子-聚乙烯亚胺（AuNPs-PEI）分别将含有SDE4310、SDE4435或SDE4955的重组质粒导入柑橘叶片。结果表明，利用该瞬时表达系统，SDE4310、SDE4435和SDE4955在柑橘叶片中成功表达，并且发现SDE4310、SDE4435和SDE4955可通过降低柑橘免疫基因的表达来促进CLas的增殖。此外，我们利用AuNPs-PEI将小干扰RNA（siRNA）导入柑橘细胞，在3天内显著降低了SDE4310的表达。虽然抑制SDE4310的表达并未抑制CLas的增殖，但它增加了CsPR1、CsNPR1和CsBIK1的表达水平。这也是首次发现AuNPs-PEI能够将外源质粒导入柑橘细胞并表达目标蛋白，为未来柑橘HLB的研究提供了一种新方法。
