Tromas Nicolas, Zwart Mark P, Lafforgue Guillaume, Elena Santiago F
Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, València, Spain.
Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, València, Spain ; The Santa Fe Institute, Santa Fe, New Mexico, United States of America.
PLoS Genet. 2014 Feb 27;10(2):e1004186. doi: 10.1371/journal.pgen.1004186. eCollection 2014 Feb.
A multicellular organism is not a monolayer of cells in a flask; it is a complex, spatially structured environment, offering both challenges and opportunities for viruses to thrive. Whereas virus infection dynamics at the host and within-cell levels have been documented, the intermediate between-cell level remains poorly understood. Here, we used flow cytometry to measure the infection status of thousands of individual cells in virus-infected plants. This approach allowed us to determine accurately the number of cells infected by two virus variants in the same host, over space and time as the virus colonizes the host. We found a low overall frequency of cellular infection (<0.3), and few cells were coinfected by both virus variants (<0.1). We then estimated the cellular contagion rate (R), the number of secondary infections per infected cell per day. R ranged from 2.43 to values not significantly different from zero, and generally decreased over time. Estimates of the cellular multiplicity of infection (MOI), the number of virions infecting a cell, were low (<1.5). Variance of virus-genotype frequencies increased strongly from leaf to cell levels, in agreement with a low MOI. Finally, there were leaf-dependent differences in the ease with which a leaf could be colonized, and the number of virions effectively colonizing a leaf. The modeling of infection patterns suggests that the aggregation of virus-infected cells plays a key role in limiting spread; matching the observation that cell-to-cell movement of plant viruses can result in patches of infection. Our results show that virus expansion at the between-cell level is restricted, probably due to the host environment and virus infection itself.
多细胞生物体并非培养瓶中的单层细胞；它是一个复杂的、具有空间结构的环境，为病毒的繁衍提供了挑战与机遇。尽管已经记录了病毒在宿主和细胞内水平的感染动态，但细胞间水平的中间环节仍知之甚少。在这里，我们使用流式细胞术来测量病毒感染植物中数千个单个细胞的感染状态。这种方法使我们能够准确确定同一宿主中两种病毒变体在病毒侵染宿主的过程中，在空间和时间上感染的细胞数量。我们发现细胞感染的总体频率较低（<0.3），同时被两种病毒变体共同感染的细胞很少（<0.1）。然后，我们估计了细胞传染率（R），即每个被感染细胞每天的二次感染数量。R的范围从2.43到与零无显著差异的值，并且通常随时间下降。感染复数（MOI）的估计值较低，即感染一个细胞的病毒粒子数量较低（<1.5）。病毒基因型频率的方差从叶片水平到细胞水平显著增加，这与低MOI一致。最后，叶片在被侵染的难易程度以及有效侵染叶片的病毒粒子数量方面存在依赖于叶片的差异。感染模式建模表明，病毒感染细胞的聚集在限制传播中起关键作用；这与植物病毒细胞间运动可导致感染斑块的观察结果相符。我们的结果表明，病毒在细胞间水平的扩散受到限制，这可能是由于宿主环境和病毒感染本身所致。
