RESUMEN
The sequence of the chloroplast genome, which is inherited maternally, contains useful information for many scientific fields such as plant systematics, biogeography and biotechnology because its characteristics are highly conserved among species. There is an increase in chloroplast genomes of angiosperms that have been sequenced in recent years. In this study, the nucleotide sequence of the chloroplast genome (cpDNA) of Veratrum patulum Loes. (Melanthiaceae, Liliales) was analyzed completely. The circular double-stranded DNA of 153,699 bp consists of two inverted repeat (IR) regions of 26,360 bp each, a large single copy of 83,372 bp, and a small single copy of 17,607 bp. This plastome contains 81 protein-coding genes, 30 distinct tRNA and four genes of rRNA. In addition, there are six hypothetical coding regions (ycf1, ycf2, ycf3, ycf4, ycf15 and ycf68) and two open reading frames (ORF42 and ORF56), which are also found in the chloroplast genomes of the other species. The gene orders and gene contents of the V. patulum plastid genome are similar to that of Smilax china, Lilium longiflorum and Alstroemeria aurea, members of the Smilacaceae, Liliaceae and Alstroemeriaceae (Liliales), respectively. However, the loss rps16 exon 2 in V. patulum results in the difference in the large single copy regions in comparison with other species. The base substitution rate is quite similar among genes of these species. Additionally, the base substitution rate of inverted repeat region was smaller than that of single copy regions in all observed species of Liliales. The IR regions were expanded to trnH_GUG in V. patulum, a part of rps19 in L. longiflorum and A. aurea, and whole sequence of rps19 in S. china. Furthermore, the IGS lengths of rbcL-accD-psaI region were variable among Liliales species, suggesting that this region might be a hotspot of indel events and the informative site for phylogenetic studies in Liliales. In general, the whole chloroplast genome of V. patulum, a potential medicinal plant, will contribute to research on the genetic applications of this genus.
Asunto(s)
Cloroplastos/genética , Genoma del Cloroplasto , Genómica , Filogenia , ARN de Planta/genética , Veratrum/genética , Cloroplastos/clasificación , Mapeo Cromosómico , ADN Circular , Secuencias Invertidas Repetidas , Liliaceae/clasificación , Liliaceae/genética , ARN de Planta/clasificación , ARN Ribosómico/clasificación , ARN Ribosómico/genética , ARN de Transferencia/clasificación , ARN de Transferencia/genética , Smilacaceae/clasificación , Smilacaceae/genética , Veratrum/clasificaciónRESUMEN
5-Methylaminomethyl-2-selenouridine (mnm(5)Se(2)U) is found in the first position of the anticodon in certain tRNAs from bacteria, archaea and eukaryotes. This selenonucleoside is formed in Escherichia coli from the corresponding thionucleoside mnm(5)S(2)U by the monomeric enzyme YbbB. This nucleoside is present in the tRNA of Methanococcales, yet the corresponding 2-selenouridine synthase is unknown in archaea and eukaryotes. Here we report that a bipartite ybbB ortholog is present in all members of the Methanococcales. Gene deletions in Methanococcus maripaludis and in vitro activity assays confirm that the two proteins act in trans to form in tRNA a selenonucleoside, presumably mnm(5)Se(2)U. Phylogenetic data suggest a primal origin of seleno-modified tRNAs.
Asunto(s)
Proteínas Arqueales/metabolismo , Methanococcus/genética , Compuestos de Organoselenio/metabolismo , ARN de Transferencia/metabolismo , Selenio/metabolismo , Tiosulfato Azufretransferasa/metabolismo , Uridina/análogos & derivados , Secuencia de Aminoácidos , Animales , Proteínas Arqueales/química , Proteínas Arqueales/clasificación , Proteínas Arqueales/genética , Ligasas/química , Ligasas/clasificación , Ligasas/genética , Ligasas/metabolismo , Methanococcus/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Compuestos de Organoselenio/química , Filogenia , Estructura Terciaria de Proteína , ARN de Transferencia/clasificación , ARN de Transferencia/genética , Alineación de Secuencia , Tiosulfato Azufretransferasa/química , Tiosulfato Azufretransferasa/genética , Uridina/química , Uridina/genética , Uridina/metabolismoRESUMEN
Proteins containing the 21st amino acid selenocysteine (Sec) are present in the three domains of life. However, within lower eukaryotes, particularly parasitic protists, the dependence on the trace element selenium is variable as many organisms lost the ability to utilize Sec. Herein, we analyzed the genomes of Trypanosoma and Leishmania for the presence of genes coding for Sec-containing proteins. The selenoproteomes of these flagellated protozoa have three selenoproteins, including distant homologs of mammalian SelK and SelT, and a novel multidomain selenoprotein designated SelTryp. In SelK and SelTryp, Sec is near the C-terminus, and in all three selenoproteins, it is within predicted redox motifs. SelTryp has neither Sec- nor cysteine-containing homologs in the human host and appears to be a Kinetoplastida-specific protein. The use of selenium for protein synthesis was verified by metabolically labeling Trypanosoma cells with 75Se. In addition, genes coding for components of the Sec insertion machinery were identified in the Kinetoplastida genomes. Finally, we found that Trypanosoma brucei brucei cells were highly sensitive to auranofin, a compound that specifically targets selenoproteins. Overall, these data establish that Trypanosoma, Leishmania and likely other Kinetoplastida utilize and depend on the trace element selenium, and this dependence is due to occurrence of selenium in at least three selenoproteins.