Moritz Thran

Suche


C2 Functional analysis of the interaction between host chaperones and viral transport proteins

Principal investigator
Uwe Sonnewald

Mentor
Alexander Steinkasserer

PhD exam: 20.12.2012

Identification and Characterization of Silencing Suppressors in Arabidopsis

Post-transcriptional gene silencing (PTGS) often limits the overexpression of transgenes in transgenic plants. It involves RNA DEPENDENT RNA POLYMERASE 6 (RDR6), which recognizes aberrant transcripts, such as inaccurately processed or uncapped mRNA and consequently triggers silencing of target transcripts.
The thesis aims to isolate and characterize Arabidopsis mutants displaying increased transgene silencing (its). One candidate mutant designated as its1 was identified and characterized. Reduced accumulation of transgene mRNA in the its1 mutant background was accompanied by an accumulation of transgene specific siRNAs and could be overcome by potyvirus infection. Therefore, we speculated that ITS1 is a suppressor of PTGS. Map-based cloning and subsequent complementation revealed that ITS1 encodes DECAPPING 2 (DCP2), which is crucial for decapping, a prerequisite for mRNA degradation. In agreement with the proposed function of DCP2 we found a reduced accumulation of uncapped mRNA within its1 mutants. Furthermore, silencing in its1 was dependent on RDR6 function suggesting that reduced decapping leads to an accumulation of aberrant capped mRNA. Hence, we provide evidence for a class of aberrant mRNA which accumulates upon impaired mRNA decapping and triggers PTGS in Arabidopsis.

 

Figure:(left) Transgenes, such as eGFP are target of PTGS in the its1 mutant background. Silencing in its1 can be overcome by TuMV infection and by loss of RDR6.
(right) The interplay between mRNA decay and PTGS in Arabidopsis. Intermediates of mRNA decay can serve as substrates for RDR6 mediated PTGS.

 

Publications

Thran, M., Link, K. and Sonnewald, U. (2012). The Arabidopsis DCP2 gene is required for proper mRNA turnover and prevents transgene silencing in Arabidopsis. Plant J 72(3), 368-377.

 

Presentations

July 2012 4th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
The Arabidopsis DCP2 gene is required for proper mRNA turnover and prevents transgene silencing in Arabidopsis
Talk
     
October 2011 First International SFB 796 Conference: Mechanisms of viral host cell manipulations: from plants to humans, Bamberg, Germany
Loss of DCP2 triggers gene silencing in Arabidopsis
Poster
     
July 2011 3rd Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Loss of DCP2 triggers gene silencing in Arabidopsis
Talk and Poster
     
September 2010 2nd Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Identification of silencing suppressors in Arabidopsis
Talk
     
September 2009 First Annual Retreat, Erlangen School of Molecular Communication, Schloss Atzelsberg, Atzelsberg, Germany
Identification of silencing suppressors in Arabidopsis
Talk
     
September 2009 Botanikertagung 2009 – Plants for the future, Leipzig, Germany
Reduced mRNA stability in rsx1-1 mutant Arabidopsis plants suggests a role of a pectate lyase like protein in gene silencing
Poster

 

Awards

Poster Award
First International SFB 796 Conference: Mechanisms of viral host cell manipulations: from plants to humans
Bamberg, Germany, October 2011
Loss of DCP2 triggers gene silencing in Arabidopsis.