Molecular analysis of ARGONAUTE7 function

• Applicant: Professor Dr. Alexis Maizel
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2013 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 227756690

• Final Report Year: 2017

Final Report Abstract

Plants produce specific small RNA molecules called small interfering RNA (siRNA) which are produced by cleavage of perfectly double stranded RNA molecules generated by RNA dependent RNA polymerases (RDRs). siRNA have role in antiviral defence but also important endogenous functions, including the control of chromatin structure and the regulation of cellular gene expression. A sub class of these siRNA, called trans acting (ta-)siRNAs are produced by the initial ARGONAUTE (AGO)/microRNA (miR)-mediated cleavage of TAS RNAs which subsequently are processed by RDR to generate siRNAs. This mode of production is evolutionary ancient and has been implicated in several aspects of plant development including leaf patterning and root growth. The ta-siRNA pathway allows amplification of the effect of the miRNA and also of the propagation of its effects several cells away, as siRNA have been shown to be mobile. What determines how, upon miRNA cleavage, only TAS precursors but not any other miRNA-cleaved mRNA, enter the siRNA pathway is unknown. Unravelling this mystery is essential for our understanding of the RNA silencing machinery. In this project, we aimed at determining how the ARGONAUTE protein AGO7 efficiently trigger production of siRNA. For this we devised an approach based on building chimera proteins between AGO7 and AGO1 a related protein which only conditionally leads to production of ta-siRNAs. Unfortunately this approach revealed technically difficult to carry on and we had to resort to alternative approaches. We could identify a domain of AGO7 which is well conserved and not found in AGO1. We identified two new proteins that are interacting with AGO7 via this domain. The characterisation of these two new proteins is ongoing.

Publications

• (2014). Post-transcriptional regulation in root development. Wiley Interdiscip Rev RNA 5, 679–696
  Stauffer, E., and Maizel, A.
  
• (2014). Traffic into silence: endomembranes and posttranscriptional RNA silencing. EMBO J. 33, 968–980
  Kim, Y.J., Maizel, A., and Chen, X.