For viroids, pollen transmission is an important transmission pathway to progeny seeds and new hosts. In the current study, we found that Tomato planta macho viroid (TPMVd)—but not Potato spindle tuber viroid (PSTVd)—was horizontally transmitted by pollen from petunia plants. Using tissue-printing hybridization to track the changes in viroid distribution after pollination, we noted that TPMVd was present in petunia stigma, styles, and eventually ovaries, whereas PSTVd was detected in the stigma and upper style but not the ovary. These findings suggest that horizontal transmission of viroids depends on the infection of the lower style and ovary during the elongation of pollen tubes after pollination. Additionally, TPMVd was transmitted horizontally, leading to systematic infection, when we used TPMVd-infected petunia pollen to pollinate the flowers of healthy tomato plants. Fertilization typically does not occur after heterologous pollination and thus likely is not required to accomplish horizontal transmission of viroids.

对于类病毒，花粉传播是后代种子和新宿主的重要传播途径。在当前的研究中，我们发现了番茄大男子气概的类固醇（TPMVd），但没有发现马铃薯纺锤块茎状的类固醇（PSTVd）-由矮牵牛植物的花粉水平传播。使用组织印刷杂交追踪授粉后类病毒分布的变化，我们注意到TPMVd存在于矮牵牛的柱头，花柱和最终的卵巢中，而PSTVd以柱头和上部花柱而不是卵巢出现。这些发现表明类病毒的水平传播取决于授粉后花粉管伸长过程中下部花粉和卵巢的感染。此外，当我们使用TPMVd感染的矮牵牛花粉对健康番茄植株的花朵进行授粉时，TPMVd水平传播，从而导致系统感染。在异源授粉后通常不会发生受精，因此可能不需要完成类病毒的水平传播。