endres, matthew , xin, ge , bowman, lewis , vance, vicki .
HC-Pro suppression of RNA silencing requires the putative transcription factor RAV2 .
RNA silencing is a conserved RNA degradation mechanism that targets invading nucleic acids such as viruses, transgenes or transposons. Helper component proteinase (HC-Pro) is a viral protein that suppresses RNA silencing in plants. In addition to being suppressed for silencing, transgenic plants expressing HC-Pro exhibit developmental anomalies and have defects in the microRNA (miRNA) pathway. Here we report the identification of a tobacco DNA binding protein (termed ntRAV) that interacts with HC-Pro in the yeast two-hybrid system. Initial experiments in tobacco suggested that ntRAV plays a role in silencing. Over-expression of ntRAV impaired transgene silencing whereas reduction in ntRAV levels resulted in acceleration of the onset of silencing. We hypothesize that ntRAV encodes an endogenous suppressor of RNA silencing that may act early in development to regulate the onset of RNA silencing. To determine if ntRAV is required for any aspect of HC-Pro function, we took advantage of tools available in the model genetic plant Arabidopsis thaliana. Salk line 070847 carrying a T-DNA insert in the RAV2 gene, an Arabidopsis gene closely related to ntRAV, was obtained and characterized. F2 plants carrying the HC-Pro transgene in the rav2 knockout background were generated. In the absence of RAV2, HC-Pro expressing plants lost the ability to suppress silencing induced by a geminivirus. Additionally, HC-Pro-associated developmental anomalies were also nearly alleviated. In contrast, HC-Pro-associated defects in miRNA biogenesis and function were largely independent of RAV2. These results demonstrate that the effects of HC-Pro on the miRNA pathway can be uncoupled from its effects on development and suppression of RNA silencing.
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1 - university of south carolina, biology, 700 sumter street, coker life sciences bldg rm#601, columbia, sc, 29205, usa
2 - university of south carolina, biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM