Citrus leprosis virus C (CiLV-C, genus Cilevirus, family Kitaviridae) is an atypical virus that does not spread systemically in its plant hosts. Upon its inoculation by Brevipalpus mites, only localized lesions occur, and the infection remains limited to cells around mite feeding sites. Here, we aimed to gain insights into the putative causes of viral unfitness in plants by expanding the limited knowledge of the molecular mechanisms underlying plant/kitavirid interactions. Firstly, we quantified the CiLV-C viral RNAs during the infection in Arabidopsis thaliana plants using RT-qPCR and systematized it by defining three stages of distinguishing subgenomic and genomic RNA accumulation: i) 0–24 h after infestation, ii) 2–4 days after infestation (dai), and iii) 6–10 dai. Accordingly, the global plant response to CiLV-C infection was assessed by RNA-Seq at each period. Results indicated a progressive reprogramming of the plant transcriptome in parallel to the increasing viral loads. Gene ontology enrichment analysis revealed the induction of cell growth-related processes at the early stages of the infection and the triggering of the SA-mediated pathway, ROS burst and hypersensitive response (HR) at the presymptomatic stage. Conversely, infected plants downregulated JA/ET-mediated pathways and processes involved in the primary metabolism including photosynthesis. Marker genes of unfolded protein response were also induced, suggesting a contribution of the endoplasmic reticulum stress to the cell death caused by the viral infection. Finally, we transiently expressed CiLV-C proteins in Nicotiana benthamiana plants to undertake their roles in the elicited plant responses. Expression of the CiLV-C P61 protein consistently triggered ROS burst, upregulated SA- and HR-related genes, increased SA levels, reduced JA levels, and caused cell death. Mimicry of responses typically observed during CiLV-C–plant interaction indicates P61 as a putative viral effector causing the HR-like symptoms associated with the infection. Our data strengthen the hypothesis that symptoms of CiLV-C infection might be the outcome of a hypersensitive-like response during an incompatible interaction. Consequently, the locally restricted infection of CiLV-C, commonly observed across infections by kitavirids, supports the thesis that these viruses, likely arising from an ancestral arthropod-infecting virus, are unable to fully circumvent plant defenses.

柑橘麻风病病毒C（CiLV-C，属 轮状病毒，家人 avi科）是一种非典型病毒，不会在其植物宿主中系统传播。接种后短足猫在螨虫中，仅发生局部病变，并且感染仍然限于螨虫摄食部位周围的细胞。在这里，我们的目标是通过扩大对植物/ kitavirid相互作用基础的分子机制的了解，以了解植物中病毒不适当的可能原因。首先，我们在感染期间对CiLV-C病毒RNA进行了定量拟南芥植物使用RT-qPCR并通过定义区分亚基因组和基因组RNA积累的三个阶段将其系统化：i）侵染后0–24 h，ii）侵染（dai）后2–4天，iii）6–10 dai。因此，在每个时期通过RNA-Seq评估了全球植物对CiLV-C感染的反应。结果表明，与病毒载量的增加并行，植物转录组的逐步重编程。基因本体富集分析显示在感染的早期诱导细胞生长相关过程，并在症状发生前触发SA介导的途径，ROS爆发和超敏反应（HR）。相反，受感染植物下调了JA / ET介导的途径和过程，这些途径和过程涉及包括光合作用在内的主要代谢。还诱导了未反应蛋白反应的标记基因，表明内质网应激对病毒感染引起的细胞死亡的贡献。最后，我们瞬时表达了CiLV-C蛋白烟草植物在引起的植物反应中发挥作用。CiLV-C P61蛋白的表达持续触发ROS爆发，上调SA和HR相关基因，增加SA水平，降低JA水平并引起细胞死亡。在CiLV-C-植物相互作用期间通常观察到的反应模仿表明P61是假定的病毒效应子，可引起与感染相关的HR样症状。我们的数据强化了以下假设：CiLV-C感染的症状可能是在不相容的相互作用过程中类似超敏反应的结果。因此，通常在kitaviridus的各种感染中观察到的局部受限制的CiLV-C感染支持以下论点：这些病毒可能源自祖传节肢动物感染病毒，无法完全避开植物防御。