PLANT PHYSIOLOGY , Vol 106, Issue 1 303-311, Copyright © 1994 by American Society of Plant Biologists
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MOLECULAR BIOLOGY AND GENE REGULATION |
An Arabidopsis Chloroplast RNA-Binding Protein Gene Encodes Multiple mRNAs with Different 5[prime] Ends
S. H. Cheng, K. Cline and A. J. DeLisle
Biochemistry Department, University of Nevada, Reno, Nevada 89557-0014 (S.-H.C., A.J.D.)
An Arabidopsis cDNA (Atrbp33) encoding a nuclear-encoded chloroplast
RNA-binding protein (RBP) has been isolated (A.J.DeLisle [1993] Plant
Physiol 102: 313-314). ATRBP33 shares global structural homology with all
known chloroplast RBPs: a chloroplast transit peptide in the amino
terminus, followed by a unique acidic domain and a tandem pair of
ribonucleoprotein consensus sequence-type RNA-binding domains in the
carboxyl end. In vitro translation products of Atrbp33 were found to be
imported into chloroplasts, suggesting that ATRBP33 is localized in
chloroplasts. The expression of Atrbp33 was higher in
chloroplast-containing organs than in nonchloroplast-containing organs.
Furthermore, Atrbp33 was expressed in a light-dependent manner. These
features are consistent with its postulated role in posttranscriptional
control of chloroplast genes. Northern analyses and RNase protection assays
showed that as many as nine messages are encoded by the single Atrbp33
gene. Sequence analysis of the cDNAs indicated that some of the transcripts
have truncated 5[prime] ends. Most interestingly, the multiple mRNAs
potentially encode different polypeptides, one of which lacks a chloroplast
transit peptide and acidic domain and contains only one intact RNA-binding
domain. Unlike the chloroplast-localized ATRBP33, the truncated polypeptide
may function in other cellular compartments.
