Mitter Neena, Sulistyowati Emy, Dietzgen Ralf G
Queensland Department of Primary Industries, Agency for Food and Fibre Sciences, Agricultural Biotechnology and Cooperative Research Centre for Tropical Plant Protection, The University of Queensland, St. Lucia Qld 4072, Australia.
Mol Plant Microbe Interact. 2003 Oct;16(10):936-44. doi: 10.1094/MPMI.2003.16.10.936.
Post-transcriptional gene silencing (PTGS), an intrinsic plant defense mechanism, can be efficiently triggered by double stranded (ds)RNA-producing transgenes and can provide high level virus resistance by specific targeting of cognate viral RNA. The discovery of virus-encoded suppressors of PTGS led to concerns about the stability of such resistance. Here, we show that Cucumber mosaic virus (CMV) is able to suppress dsRNA-induced PTGS and the associated Potato virus Y (PVY) immunity in tobacco. CMV suppression supported only a transient PVY accumulation and did not prevent recovery of the transgenic plants from PVY infection. CMV inoculation resulted in strongly increased transgene mRNA levels due to suppression of PTGS, but accumulation of PVY-specific small interfering (si)RNA was unaffected. However, PVY accumulation in previously immune plants resulted in increased PVY siRNA levels and transgene mRNA was no longer detected, despite the presence of CMV. Transgene mRNA returned to high levels once PVY was no longer detected in CMV-infected plants. Recovered and chronically CMV-infected tissues were immune to further PVY infection.
转录后基因沉默（PTGS）是植物固有的一种防御机制，可被产生双链（ds）RNA的转基因有效触发，并能通过特异性靶向同源病毒RNA提供高水平的病毒抗性。病毒编码的PTGS抑制子的发现引发了人们对这种抗性稳定性的担忧。在此，我们表明黄瓜花叶病毒（CMV）能够抑制烟草中dsRNA诱导的PTGS以及相关的马铃薯Y病毒（PVY）免疫。CMV的抑制作用仅支持PVY的短暂积累，并且不能阻止转基因植物从PVY感染中恢复。由于PTGS受到抑制，CMV接种导致转基因mRNA水平大幅增加，但PVY特异性小干扰（si）RNA的积累未受影响。然而，在先前免疫的植物中，PVY的积累导致PVY siRNA水平升高，尽管存在CMV，但转基因mRNA不再被检测到。一旦在CMV感染的植物中未再检测到PVY，转基因mRNA就会恢复到高水平。恢复的和长期受CMV感染的组织对进一步的PVY感染具有免疫力。
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