Global key players of chloroplast gene expression

• Applicant: Privatdozent Dr. Jörg Meurer
• Subject Area: Plant Biochemistry and Biophysics ; Plant Genetics and Genomics
• Term: from 2013 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 238561773

The chloroplast Ribonuclease E (RNE) plays an important key role in processing of many transcripts and therefore belongs to the major RNA processing factors in chloroplasts. By means of forward and reverse genetics in Arabidopsis and tagging approaches in combination with mass spectrometry we recently identified a degradosome-like complex (DLC), which contains RNE, RNJ, one helicase, two ribosomal proteins with presumably extraribosomal functions and unknown proteins, like RHON1 and a pentatricopeptide repeat (PPR) protein. A degradosome was previously thought not to exist in chloroplasts. The essential and plant specific RHON1 protein was found to bind specifically to those RNA regions, which are not processed efficiently in rne and rhon1 mutants. Therefore, we hypothesize that RHON1 supports the function of RNE presumably by delivering the target RNAs to the DLC. Interestingly, rne and rhon1 mutants have numerous and tiny chloroplasts strongly supporting an important role in plastid division. Another global player in plastid gene expression is represented by pale cress (PAC). We showed that PAC directly interacts with proteins and RNA. This project aims to analyse the function and importance of interaction partners of RNE, RHON1 and PAC, to identify the precise RNA targets of PAC and to investigate a putative regulatory role in plastid gene expression and the function of PAC in ribosome assembly. We anticipate that future research on the DLC and PAC, their compartmentalization within the chloroplast and association partners will shed new light on chloroplast gene expression, division and development.

• DFG Programme: Research Grants