Putative Group I Introns in the Nuclear Internal Transcribed Spacer of the Basidiomycete Fungus Gautieria Vittad

2021 ◽  
Vol 55 (5) ◽  
pp. 471-479
Author(s):  
Ergin Sahin
Keyword(s):  
Internal Transcribed Spacer ◽  
Group I Introns ◽  
Group I ◽  
Basidiomycete Fungus

scholarly journals Organellar Introns in Fungi, Algae, and Plants

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 2001
Author(s):  
Jigeesha Mukhopadhyay ◽  
Georg Hausner
Keyword(s):  
Gene Expression ◽  
Ribosomal Proteins ◽  
Heterologous Gene Expression ◽  
Group I Introns ◽  
Group Ii Introns ◽  
Homing Endonucleases ◽  
Organellar Genomes ◽  
Chloroplast Genomes ◽  
Group I ◽  
Group Ii

Introns are ubiquitous in eukaryotic genomes and have long been considered as ‘junk RNA’ but the huge energy expenditure in their transcription, removal, and degradation indicate that they may have functional significance and can offer evolutionary advantages. In fungi, plants and algae introns make a significant contribution to the size of the organellar genomes. Organellar introns are classified as catalytic self-splicing introns that can be categorized as either Group I or Group II introns. There are some biases, with Group I introns being more frequently encountered in fungal mitochondrial genomes, whereas among plants Group II introns dominate within the mitochondrial and chloroplast genomes. Organellar introns can encode a variety of proteins, such as maturases, homing endonucleases, reverse transcriptases, and, in some cases, ribosomal proteins, along with other novel open reading frames. Although organellar introns are viewed to be ribozymes, they do interact with various intron- or nuclear genome-encoded protein factors that assist in the intron RNA to fold into competent splicing structures, or facilitate the turn-over of intron RNAs to prevent reverse splicing. Organellar introns are also known to be involved in non-canonical splicing, such as backsplicing and trans-splicing which can result in novel splicing products or, in some instances, compensate for the fragmentation of genes by recombination events. In organellar genomes, Group I and II introns may exist in nested intronic arrangements, such as introns within introns, referred to as twintrons, where splicing of the external intron may be dependent on splicing of the internal intron. These nested or complex introns, with two or three-component intron modules, are being explored as platforms for alternative splicing and their possible function as molecular switches for modulating gene expression which could be potentially applied towards heterologous gene expression. This review explores recent findings on organellar Group I and II introns, focusing on splicing and mobility mechanisms aided by associated intron/nuclear encoded proteins and their potential roles in organellar gene expression and cross talk between nuclear and organellar genomes. Potential application for these types of elements in biotechnology are also discussed.

scholarly journals Mutations in nuclear gene cyt-4 of Neurospora crassa result in pleiotropic defects in processing and splicing of mitochondrial RNAs.

Genetics ◽  
1989 ◽  
Vol 123 (1) ◽  
pp. 97-108 ◽  
Author(s):  
K F Dobinson ◽  
M Henderson ◽  
R L Kelley ◽  
R A Collins ◽  
A M Lambowitz
Keyword(s):  
Neurospora Crassa ◽  
Mitochondrial Protein ◽  
Nuclear Gene ◽  
Northern Hybridization ◽  
Rrna Gene ◽  
Mitochondrial Rna ◽  
Group I Introns ◽  
Group I ◽  
Processing Pathways ◽  
Aberrant Rna

Abstract The nuclear cyt-4 mutants of Neurospora crassa have been shown previously to be defective in splicing the group I intron in the mitochondrial large rRNA gene and in 3' end synthesis of the mitochondrial large rRNA. Here, Northern hybridization experiments show that the cyt-4-1 mutant has alterations in a number of mitochondrial RNA processing pathways, including those for cob, coI, coII and ATPase 6 mRNAs, as well as mitochondrial tRNAs. Defects in these pathways include inhibition of 5' and 3' end processing, accumulation of aberrant RNA species, and inhibition of splicing of both group I introns in the cob gene. The various defects in mitochondrial RNA synthesis in the cyt-4-1 mutant cannot be accounted for by deficiency of mitochondrial protein synthesis or energy metabolism, and they suggest that the cyt-4-1 mutant is defective in a component or components required for processing and/or turnover of a number of different mitochondrial RNAs. Defective splicing of the mitochondrial large rRNA intron in the cyt-4-1 mutant may be a secondary effect of failure to synthesize pre-rRNAs having the correct 3' end. However, a similar explanation cannot be invoked to account for defective splicing of the cob pre-mRNA introns, and the cyt-4-1 mutation may directly affect splicing of these introns.

The Origin and Evolution of Protist Group I Introns

Protist ◽  
1998 ◽  
Vol 149 (2) ◽  
pp. 113-122 ◽  
Author(s):  
Debashish Bhattacharya
Keyword(s):  
Group I Introns ◽  
Origin And Evolution ◽  
Group I

scholarly journals Mobile Self-Splicing Group I Introns from thepsbA Gene of Chlamydomonas reinhardtii: Highly Efficient Homing of an Exogenous Intron Containing Its Own Promoter

2001 ◽  
Vol 21 (10) ◽  
pp. 3472-3481 ◽  
Author(s):  
Obed W. Odom ◽  
Stephen P. Holloway ◽  
Nita N. Deshpande ◽  
Jaesung Lee ◽  
David L. Herrin
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Open Reading Frames ◽  
Group I Introns ◽  
Resistance Marker ◽  
Free Standing ◽  
Spectinomycin Resistance ◽  
Highly Efficient ◽  
Group I ◽  
Short Exon ◽  
Self Splicing

ABSTRACT Introns 2 and 4 of the psbA gene of Chlamydomonas reinhardtii chloroplasts (Cr.psbA2 andCr.psbA4, respectively) contain large free-standing open reading frames (ORFs). We used transformation of an intronless-psbA strain (IL) to test whether these introns undergo homing. Each intron, plus short exon sequences, was cloned into a chloroplast expression vector in both orientations and then cotransformed into IL along with a spectinomycin resistance marker (16Srrn). For Cr.psbA2, the sense construct gave nearly 100% cointegration of the intron whereas the antisense construct gave 0%, consistent with homing. For Cr.psbA4, however, both orientations produced highly efficient cointegration of the intron. Efficient cointegration of Cr.psbA4 also occurred when the intron was introduced as a restriction fragment lacking any known promoter. Deletion of most of the ORF, however, abolished cointegration of the intron, consistent with homing. TheCr.psbA4 constructs also contained a 3-(3,4-dichlorophenyl)-1,1-dimethylurea resistance marker in exon 5, which was always present when the intron integrated, thus demonstrating exon coconversion. Remarkably, primary selection for this marker gave >100-fold more transformants (>10,000/μg of DNA) than did the spectinomycin resistance marker. A trans homing assay was developed for Cr.psbA4; the ORF-minus intron integrated when the ORF was cotransformed on a separate plasmid. This assay was used to identify an intronic region between bp −88 and −194 (relative to the ORF) that stimulated homing and contained a possible bacterial (−10, −35)-type promoter. Primer extension analysis detected a transcript that could originate from this promoter. Thus, this mobile, self-splicing intron also contains its own promoter for ORF expression. The implications of these results for horizontal intron transfer and organelle transformation are discussed.

Group I Intron Versus its Sequences in Phylogeny of Cetrarioid Lichens

1999 ◽  
Vol 31 (5) ◽  
pp. 441-449 ◽  
Author(s):  
Arne Thell
Keyword(s):  
Ribosomal Rna ◽  
Internal Transcribed Spacer ◽  
Phylogenetic Trees ◽  
Group I Intron ◽  
Ribosomal Genes ◽  
Its Sequences ◽  
Its Sequence ◽  
Ribosomal Rna Gene ◽  
18S Ribosomal Rna Gene ◽  
Group I

AbstractPhylogenetic trees based on group I intron sequences and on internal transcribed spacer (ITS) sequences of mycobiont ribosomal genes were calculated and compared. Eight cetrarioid and four non-cetrarioid species of the Parmeliaceae were compared. The phylogeny based on group I intron sequences is partly congruent with the ITS sequence phylogeny. Group I intron sequences are presumably less informative for infragenic studies. The introns have a length of 214–233 nucleotides, and differ at up to 33% of the bases between species. All introns analysed are located between the positions 1516 and 1517 of the fungal 18S ribosomal RNA gene. Cetrarioid lichens form a non-homogeneous group within the Parmeliaceae according to both group I intron and ITS sequences.

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