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Lariat formation and a hydrolytic pathway in plant chloroplast group II intron splicing.

ABSTRACT: Lariat formation has been studied intensively only with a few self-splicing group II introns, and little is known about how the numerous diverse introns in plant organelles are excised. Several of these introns have branch-points that are not a single bulge but are adjoined by A:A, A:C, A:G and G:G pairs. Using a highly sensitive in vivo approach, we demonstrate that all but one of the barley chloroplast introns splice via the common pathway that produces a branched product. RNA editing does not improve domain 5 and 6 structures of these introns. The conserved branch-point in tobacco rpl16 is chosen even if an adjacent unpaired adenosine is available, suggesting that spatial arrangements in domain 6 determine correct branch-point selection. Lariats were not detected for the chloroplast trnV intron, which lacks an unpaired adenosine in domain 6. Instead, this intron is released as linear molecules that undergo further polyadenylation. trnV, which is conserved throughout plant evolution, constitutes the first example of naturally occurring hydrolytic group II intron splicing in vivo.

SUBMITTER: Vogel J

PROVIDER: S-EPMC126105 | biostudies-literature | 2002 Jul

REPOSITORIES: biostudies-literature

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Lariat formation and a hydrolytic pathway in plant chloroplast group II intron splicing.

Vogel Jörg J Börner Thomas T

The EMBO journal 20020701 14

Lariat formation has been studied intensively only with a few self-splicing group II introns, and little is known about how the numerous diverse introns in plant organelles are excised. Several of these introns have branch-points that are not a single bulge but are adjoined by A:A, A:C, A:G and G:G pairs. Using a highly sensitive in vivo approach, we demonstrate that all but one of the barley chloroplast introns splice via the common pathway that produces a branched product. RNA editing does not ...[more]

PMID: 12110591

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Project description:Group II introns are large catalytic RNAs (ribozymes) which are found in bacteria and organellar genomes of several lower eukaryotes, but are particularly prevalent within the mitochondrial genomes (mtDNA) in plants, where they reside in numerous critical genes. Their excision is therefore essential for mitochondria biogenesis and respiratory functions, and is facilitated in vivo by various protein cofactors. Typical group II introns are classified as mobile genetic elements, consisting of the self-splicing ribozyme and its intron-encoded maturase protein. A hallmark of maturases is that they are intron specific, acting as cofactors which bind their own cognate containing pre-mRNAs to facilitate splicing. However, the plant organellar introns have diverged considerably from their bacterial ancestors, such as they lack many regions which are necessary for splicing and also lost their evolutionary related maturase ORFs. In fact, only a single maturase has been retained in the mtDNA of various angiosperms: the matR gene encoded in the fourth intron of the NADH-dehydrogenase subunit 1 (nad1 intron 4). Their degeneracy and the absence of cognate ORFs suggest that the splicing of plant mitochondria introns is assisted by trans-acting cofactors. Interestingly, in addition to MatR, the nuclear genomes of angiosperms also harbor four genes (nMat 1-4), which are closely related to maturases and contain N-terminal mitochondrial localization signals. Recently, we established the roles of two of these paralogs in Arabidopsis, nMAT1 and nMAT2, in the splicing of mitochondrial introns. In addition to the nMATs, genetic screens led to the identification of other genes encoding various factors, which are required for the splicing and processing of mitochondrial introns in plants. In this review we will summarize recent data on the splicing and processing of mitochondrial introns and their implication in plant development and physiology, with a focus on maturases and their accessory splicing cofactors.

Dataset Information

Lariat formation and a hydrolytic pathway in plant chloroplast group II intron splicing.

Publications

Lariat formation and a hydrolytic pathway in plant chloroplast group II intron splicing.

Similar Datasets

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