Poster: Regulation of gene expression

Abs # 780: Characterization of nuclear encoded proteins that impact chloroplast translation initiation

Presenter:	Somanchi, Aravind , somanar@auburn.edu
Authors	Somanchi, Aravind  (A)   Davis, Virginia C (A)
Affiliations:	(A): Auburn University

Translation initiation involves the stepwise assembly of a translation-competent ribosome at the initiation codon of the mRNA. While translation initiation in chloroplasts is thought to be similar to that in prokaryotes, the assembly of the chloroplast translation initiation complex is not well understood. Translation initiation in prokaryotes is mediated by initiation factors that facilitate the assembly of ribosomes, mRNA and tRNA-fMet to form the initiation complex. Biochemical and genetic studies have implied that translation initiation in the chloroplast requires several nuclear encoded proteins. This suggests that several nuclear encoded protein factors may participate in both the assembly of the translation initiation complex and the modulation of translation initiation. Analysis of complete genome sequences of several photosynthetic organisms identified several nuclear encoded genes with putative chloroplast transit sequences and possible associations with mRNA, tRNA and ribosomes. We have cloned several of these genes from Chlamydomonas reinhardtii to characterize their biochemical role in the initiation and regulation of translation in the chloroplast. The cloned genes include putative translation initiation factors as well as proteins that might impact the assembly of the translation initiation complex. Chlamydomonas reinhardtii strains transformed with constructs expressing these genes containing a C-terminal tag (GFP and FLAG) will be used to establish the sub-cellular localization of these proteins. Analysis of the interaction of these proteins with chloroplast mRNAs and other associating proteins will facilitate the identification of the role they play in chloroplast translational regulation.