rośliny-i-grzyby: Intron

Evidence: 100 • authority: 72

An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word intron is derived from the term intragenic region, i.e., a region inside a gene. The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons. Introns are found in the genes of most eukaryotes and many eukaryotic viruses, and they can be located in both protein-coding genes and genes that function as RNA (noncoding genes). There are four main types of introns: tRNA introns, group I introns, group II introns, and…

Evidence: 84 • authority: 88

Distinct Expansion of Group II Introns During Evolution of Prokaryotes and Possible Factors Involved in Its Regulation. Group II introns (G2Is) are ribozymes that have retroelement characteristics in prokaryotes. Although G2Is are suggested to have been an important evolutionary factor in the prokaryote-to-eukaryote transition, comprehensive analyses of these introns among the tens of thousands of prokaryotic genomes currently available are still limited. Here, we developed a bioinformatic pipeline that systematically collects G2Is and applied it to prokaryotic genomes. We found that in bacteria, 25% (447 of 1,790) of the total representative genomes had an average of 5.3 G2Is, and in archa…

Evidence: 84 • authority: 88

Distinct Expansion of Group II Introns Depends on the Type of Intron-encoded Protein and Genomic Signatures in Prokaryotes. Abstract Group II introns (G2Is) are self-splicing ribozymes that have retroelement characteristics in prokaryotes. Although G2Is are considered an important factor in the evolution of prokaryotes, comprehensive analyses of these introns among the tens of thousands of prokaryotic genomes currently available are still limited. Here, we developed a bioinformatic pipeline that systematically collects G2Is and applied it to prokaryotic genomes. We found that in bacteria, 25% (447 of 1,790) of the total representative species had an average of 5.3 G2Is, and in archaea, 9% (…

Evidence: 67 • authority: 92

Single-cell transcriptomics reveals lateral transfers of multiple functional genes from prokaryotes to free-living ciliated protists in detrital food webs.. Lateral gene transfer (LGT) is a key driver of evolutionary innovation, underlying protists' lifestyles and interactions in anaerobic environments. Yet, its significance in free-living protists remains underexplored. Here, we address this gap by presenting the first single-cell transcriptomes of Metopus yantaiensis and genome-wide LGT screens across 36 omics datasets from nine anaerobic APM ciliates (classes Armophorea, Muranotrichea, and Parablepharismea)-a group in soil/sediment environments. Through phylogenetic analyses and validati…

Evidence: 51 • authority: 88

Putative introns in tRNA genes of prokaryotes.. Sequences of two putative tRNA genes, for serine and leucine, from the archaebacterium Sulfolobus solfataricus contain intervening sequences in the anticodon region. Furthermore, the genes lack encoded CCA 3' termini and are flanked by A + T-rich DNA segments. The introns can both form the same secondary structure, which is a double-helical extension of the anticodon stalk. The resulting structure contains two symmetrically placed 3-base bulge loops, in which are located cleavage sites for the introns. In the one case tested, the gene occurs as a single copy in the genome.

Evidence: 51 • authority: 80

Why Prokaryotes Genomes Lack Genes with Introns Processed by Spliceosomes?

Evidence: 51 • authority: 80

Self-splicing introns in prokaryotes: Migrant fossils?

Evidence: 51 • authority: 92

Mobile intron RNA from a bacterial predator accumulates in dead archaeal cells.. Introns in prokaryotes are classified as mobile genetic elements normally located within essential genes. Their RNA transcripts are functional if spliced by the intron´s ribozyme activity. The excised intron RNA is assumed to proliferate by leaving the host cell and being integrated into foreign genomes. Here we show the presence of a bacterial intron´s RNA in archaeal cells. The predatory ultramicrobial epibiont Candidatus Velamenicoccus archaeovorus contains a group I intron in its 23 S ribosomal RNA gene. In search for predation evidence, we visualized the intron RNA by in situ hybridization and observed it…