The RNA recognition motif protein CP33A is a global ligand of chloroplast mRNAs and is essential for plastid biogenesis and plant development

Plant J. 2017 Feb;89(3):472-485. doi: 10.1111/tpj.13396. Epub 2017 Jan 25.


Chloroplast RNA metabolism depends on a multitude of nuclear-encoded RNA-binding proteins (RBPs). Most known chloroplast RBPs address specific RNA targets and RNA-processing functions. However, members of the small chloroplast ribonucleoprotein family (cpRNPs) play a global role in processing and stabilizing chloroplast RNAs. Here, we show that the cpRNP CP33A localizes to a distinct sub-chloroplastic domain and is essential for chloroplast development. The loss of CP33A yields albino seedlings that exhibit aberrant leaf development and can only survive in the presence of an external carbon source. Genome-wide RNA association studies demonstrate that CP33A associates with all chloroplast mRNAs. For a given transcript, quantification of CP33A-bound versus free RNAs demonstrates that CP33A associates with the majority of most mRNAs analyzed. Our results further show that CP33A is required for the accumulation of a number of tested mRNAs, and is particularly relevant for unspliced and unprocessed precursor mRNAs. Finally, CP33A fails to associate with polysomes or to strongly co-precipitate with ribosomal RNA, suggesting that it defines a ribodomain that is separate from the chloroplast translation machinery. Collectively, these findings suggest that CP33A contributes to globally essential RNA processes in the chloroplasts of higher plants.

Keywords: Arabidopsis thaliana; RNA binding; RNA stability; RRM domain; albino; chloroplast; cpRNP; ribonucleoprotein; splicing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Chloroplast Proteins / genetics
  • Chloroplast Proteins / metabolism*
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant
  • Immunoblotting
  • Mutation
  • Plants, Genetically Modified
  • Plastids / genetics
  • Plastids / metabolism
  • Protein Binding
  • RNA Splicing
  • RNA, Chloroplast / genetics
  • RNA, Chloroplast / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Ribonucleoproteins / genetics
  • Ribonucleoproteins / metabolism*
  • Seedlings / genetics
  • Seedlings / growth & development
  • Seedlings / metabolism


  • Arabidopsis Proteins
  • Chloroplast Proteins
  • RNA, Chloroplast
  • RNA, Messenger
  • RNA-Binding Proteins
  • Ribonucleoproteins
  • chloroplast RNA-binding protein 33, Arabidopsis