Steinbachová Lenka, Matoušek Jaroslav, Steger Gerhard, Matoušková Helena, Radišek Sebastjan, Honys David
Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojová 263, 165 02 Prague 6, Czech Republic.
Biology Centre of the Czech Academy of Sciences, Department of Molecular Genetics, Institute of Plant Molecular Biology, Branišovská 31, 37005 České Budějovice, Czech Republic.
Plants (Basel). 2021 Nov 6;10(11):2398. doi: 10.3390/plants10112398.
Viroids are small, non-coding, parasitic RNAs that promote developmental distortions in sensitive plants. We analyzed pollen of after infection and/or ectopic transformation with cDNAs of citrus bark cracking viroid (CBCVd), apple fruit crinkle viroid (AFCVd) and potato spindle tuber viroid (PSTVd) variant AS1. These viroids were seed non-transmissible in . All viroids propagated to high levels in immature anthers similar to leaves, while their levels were drastically reduced by approximately 3.6 × 10, 800 and 59 times in mature pollen of CBCVd, AFCVd and PSTVd infected respectively, in comparison to leaves. These results suggest similar elimination processes during male gametophyte development as in the we presented in our previous study. Mature pollen of showed no apparent defects in infected plants although all three viroids induced strong pathological symptoms on leaves. While species have naturally bicellular mature pollen, we noted a rare occurrence of mature pollen with three nuclei in CBCVd-infected . Changes in the expression of ribosomal marker proteins in AFCVd-infected pollen were detected, suggesting some changes in pollen metabolism. transformed with 35S-driven viroid cDNAs showed strong symptoms including defects in pollen development. A large number of aborted pollen (34% and 62%) and a slight increase of young pollen grains (8% and 15%) were found in mature pollen of AFCVd and CBCVd transformants, respectively, in comparison to control plants (3.9% aborted pollen and 0.3% young pollen). Moreover, pollen grains with malformed nuclei or trinuclear pollen were found in CBCVd-transformed plants. Our results suggest that "forcing" overexpression of seed non-transmissible viroid led to strong pollen pathogenesis. Viroid adaptation to pollen metabolism can be assumed as an important factor for viroid transmissibility through pollen and seeds.
类病毒是小型、非编码的寄生性RNA，可导致敏感植物发育畸变。我们分析了柑橘裂皮类病毒（CBCVd）、苹果果皱类病毒（AFCVd）和马铃薯纺锤块茎类病毒（PSTVd）变体AS1感染和/或异位转化后的花粉。这些类病毒在[具体植物名称未给出]中不能通过种子传播。所有类病毒在未成熟花药中繁殖到高水平，类似于叶片中的情况，而与叶片相比，在感染CBCVd、AFCVd和PSTVd的[具体植物名称未给出]的成熟花粉中，它们的水平分别急剧降低了约3.6×10、800和59倍。这些结果表明，在雄配子体发育过程中存在与我们之前研究中所展示的[具体植物名称未给出]类似的消除过程。尽管所有三种类病毒在叶片上诱导出强烈的病理症状，但[具体植物名称未给出]的成熟花粉在受感染植株中未表现出明显缺陷。虽然[具体植物名称未给出]物种天然具有双细胞成熟花粉，但我们注意到在感染CBCVd的[具体植物名称未给出]中罕见地出现了具有三个细胞核的成熟花粉。在感染AFCVd的花粉中检测到核糖体标记蛋白表达的变化，表明花粉代谢发生了一些变化。用35S驱动的类病毒cDNA转化的[具体植物名称未给出]表现出强烈症状，包括花粉发育缺陷。与对照植株（3.9%的败育花粉和0.3%的幼嫩花粉）相比，在AFCVd和CBCVd转化体的成熟花粉中分别发现了大量败育花粉（34%和62%）和幼嫩花粉粒略有增加（8%和15%）。此外，在CBCVd转化植株中发现了细胞核畸形的花粉粒或三核花粉。我们的结果表明，“强制”种子不可传播类病毒的过表达会导致强烈的花粉致病作用。可以认为类病毒对花粉代谢的适应是类病毒通过花粉和种子传播的一个重要因素。
