The influence of salicylic acid and jasmonic acid on expression of RNA-dependent RNA polymerase 1 in Arabidopsis

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• Lydia Hunter
• Thursday 31 May 2012, 15:30-16:00
• Department of Plant Sciences, Large Lecture Theatre.

If you have a question about this talk, please contact Suzy Stoodley.

Cellular RNA dependent RNA polymerases (RDRs) promote the amplification of RNA silencing and RDRs1 and 6 have been shown to play roles in anti-viral silencing in plants. In tobacco RDR1 transcript levels are increased in response to a number of factors including treatment with salicylic acid (SA), an important signal in induced pathogen resistance. This has led to suggestions that RDR1 activity contributes to SA-induced resistance to viruses. However, despite the apparent importance of RDR1 , its regulation by defensive signal transduction pathways has not been investigated in detail. My PhD project investigates the role of RDR1 in reducing viral accumulation in potato plants, which was covered in some detail in my first year talk, and the regulation of RDR1 expression by plant defence pathways in Arabidopsis, which will be the focus of my third year presentation. By conducting detailed time-course experiments I have demonstrated that SA and methyljasmonic acid (MeJA), a derivative of jasmonic acid (JA), another important defensive signal, both induce transient gene expression of AtRDR1, and with very similar kinetics. Wounding Arabidopsis leaves also induces RDR1 expression, which is consistent with regulation of RDR1 expression by JA. The results are surprising because the SA- and JA-dependent signalling pathways are often antagonistic and induce distinct sets of genes. Working with Arabidopsis mutant lines harbouring defects in defensive signalling I have found that full SA-induced RDR1 expression is dependent on the transcriptional activator ‘non-expressor of pathogenesis-related genes 1’ (NPR1). Thus, the mechanism governing increased RDR1 transcription appears to be similar to that involved in the regulation of many other SA-induced defence-related genes. However, the induction of increased RDR1 transcript accumulation following MeJA is unaltered in coronatine-insensitive 1 (coi1) mutant plants. This is surprising because the majority of JA-dependent genes are dependent on the functioning of COI1 (a Skp1-Cullin1-F box) protein that mediates perception of JA. I will discuss my ongoing work on the interplay of SA, JA and potentially other signals in the regulation of this enigmatic component of RNA silencing.

This talk is part of the Plant Sciences Research Seminars series.

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