This project is a study of the structure, function, and splicing mechanisms of the group II and group III introns and twintrons (""""""""introns-within-introns"""""""") of the plastid genomes of Euglena gracilis and related protists. These organisms are the richest known source of group II introns, and have the only known group II and group III twintrons.
The specific aims i nclude: (1) Characterization of novel group II and group III introns and twintrons in species related to Euglena gracilis as a means to explore (i) possible """"""""founder"""""""" events of intron invasion, (ii) whether group II and group III intorns shared a common conserved structural motifs required for RNA splicing; (2) An investigation of the role of the group III intron spicing, and (3) Analysis of cis-acting domains of group II and group III intorns required for in vivo splicing in transgenic I. gracilis chloroplasts.
This aim will be expanded to include site-directed mutagenesis of intron maturases if sufficient technical progress in plastid transformation is achieved. This work is addressed at understanding fundamental questions about the origins and evolution of introns and twintrons. A working hypothesis is that group II and group III introns, as well as nuclear pre-mRNA spliceosomal intorns, may have all shared a common evolutionary ancestor. Therefore, studies on unusual variants among the smallest group II and group III introns should be relevant to understanding the RNA structures at the heart of all splicing reactions.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Molecular Biology Study Section (MBY)
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University of Arizona
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Sheveleva, Elena V; Hallick, Richard B (2004) Recent horizontal intron transfer to a chloroplast genome. Nucleic Acids Res 32:803-10
Sheveleva, Elena V; Giordani, Nicole V; Hallick, Richard B (2002) Identification and comparative analysis of the chloroplast alpha-subunit gene of DNA-dependent RNA polymerase from seven Euglena species. Nucleic Acids Res 30:1247-54
Doetsch, N A; Favreau, M R; Kuscuoglu, N et al. (2001) Chloroplast transformation in Euglena gracilis: splicing of a group III twintron transcribed from a transgenic psbK operon. Curr Genet 39:49-60
Doetsch, N A; Thompson, M D; Favreau, M R et al. (2001) Comparison of psbK operon organization and group III intron content in chloroplast genomes of 12 Euglenoid species. Mol Gen Genet 264:682-90
Doetsch, N A; Thompson, M D; Hallick, R B (1998) A maturase-encoding group III twintron is conserved in deeply rooted euglenoid species: are group III introns the chicken or the egg? Mol Biol Evol 15:76-86
Stevenson, J K; Hallick, R B (1994) The psaA operon pre-mRNA of the Euglena gracilis chloroplast is processed into photosystem I and II mRNAs that accumulate differentially depending on the conditions of cell growth. Plant J 5:247-60
Hong, L; Hallick, R B (1994) Gene structure and expression of a novel Euglena gracilis chloroplast operon encoding cytochrome b6 and the beta and epsilon subunits of the H(+)-ATP synthase complex. Curr Genet 25:270-81
Drager, R G; Hallick, R B (1993) A novel Euglena gracilis chloroplast operon encoding four ATP synthase subunits and two ribosomal proteins contains 17 introns. Curr Genet 23:271-80
Drager, R G; Hallick, R B (1993) A complex twintron is excised as four individual introns. Nucleic Acids Res 21:2389-94
Copertino, D W; Shigeoka, S; Hallick, R B (1992) Chloroplast group III twintron excision utilizing multiple 5'- and 3'-splice sites. EMBO J 11:5041-50

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