Post-translational modifications, but not transcriptional regulation, of major chloroplast RNA-binding proteins are related to Arabidopsis seedling development.
Chloroplast RNA-binding proteins are involved in stabilizing stored chloroplast mRNAs and in recruiting site-specific factors that mediate RNA metabolism. In the present study, we characterized two major chloroplast RNA-binding proteins, cp29A and cp29B, by MALDI-TOF MS, N-terminal sequencing, and ESI-MS/MS following 2D-PAGE separation. Polypeptides derived from cp29A were recovered with free N-terminus or with N-terminal acetylation. In addition to the two isoforms found for cp29A, an isoform derived from cp29B was also observed to have five amino acids cleaved from its N-terminus. Results of quantitative real-time RT-PCR indicate that both genes reached maximal rates of transcription 96 h after commencement of germination and maintained relatively high levels throughout the whole life cycle. Transcription of cp29A and cp29B did not vary significantly under light or dark conditions, although production of the acetylated and N-terminally cleaved protein isoforms exhibited light dependence. Exposure of etiolated Arabidopsis seedlings to light conditions for as short as 9 h restored the modified isoforms to levels similar to those found in green plants. Identification of post-translational modifications in major chloroplast RNA-binding proteins may help elucidate their roles in seedling development and in plant RNA stabilization during the greening process.
The National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing, PR China.
Bai-Chen
BC
Wang
Hong-Xia
HX
Wang
Jian-Xun
JX
Feng
Da-Zhe
DZ
Meng
Li-Jia
LJ
Qu
Yu-Xian
YX
Zhu
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D002736:Chloroplasts / Q000737:chemistry* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D008027:Light; D008969:Molecular Sequence Data; D018521:Plant Physiological Phenomena; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D040901:Proteomics / Q000379:methods*; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins / Q000737:chemistry*; D036226:Seedlings / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D016601:RNA-Binding Proteins