RNase J participates in a pentatricopeptide repeat protein-mediated 5' end maturation of chloroplast mRNAs.
Nucleus-encoded ribonucleases and RNA-binding proteins influence chloroplast gene expression through their roles in RNA maturation and stability. One mechanism for mRNA 5' end maturation posits that sequence-specific pentatricopeptide repeat (PPR) proteins define termini by blocking the 5'→3' exonucleolytic activity of ribonuclease J (RNase J). To test this hypothesis in vivo, virus-induced gene silencing was used to reduce the expression of three PPR proteins and RNase J, both individually and jointly, in Nicotiana benthamiana. In accordance with the stability-conferring function of the PPR proteins PPR10, HCF152 and MRL1, accumulation of the cognate RNA species atpH, petB and rbcL was reduced when the PPR-encoding genes were silenced. In contrast, RNase J reduction alone or combined with PPR deficiency resulted in reduced abundance of polycistronic precursor transcripts and mature counterparts, which were replaced by intermediately sized species with heterogeneous 5' ends. We conclude that RNase J deficiency can partially mask the absence of PPR proteins, and that RNase J is capable of processing chloroplast mRNAs up to PPR protein-binding sites. These findings support the hypothesis that RNase J is the major ribonuclease responsible for maturing chloroplast mRNA 5' termini, with RNA-binding proteins acting as barriers to its activity.
Boyce Thompson Institute for Plant Research, Ithaca, New York 14850, USA and Hawkesbury Institute for the Environment, University of Western Sydney, Richmond 2753, Australia.
Scott
S
Luro
Arnaud
A
Germain
Robert E
RE
Sharwood
David B
DB
Stern
D018506:Gene Expression Regulation, Plant; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional; D018747:RNA, Chloroplast / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012343:RNA, Transfer / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D012260:Ribonucleases / Q000378:metabolism* / Q000502:physiology; D014026:Nicotiana / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism
D010940:Plant Proteins; D018747:RNA, Chloroplast; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012343:RNA, Transfer; D012260:Ribonucleases