Most tooth-bearing non-mammalian vertebrates have the capacity to replace their teeth throughout life. This capacity was lost in mammals, which replace their teeth only once at most. Not surprisingly, continuous tooth replacement has attracted much attention. Classical morphological studies (e.g. to analyse patterns of replacement) are now being complemented by molecular studies that investigate the expression of genes involved in tooth formation. This review focuses on ray-finned fish (actinopterygians), which have teeth often distributed throughout the mouth and pharynx, and more specifically on teleost fish, the largest group of extant vertebrates. First we highlight the diversity in tooth distribution and in tooth replacement patterns. Replacement tooth formation can start from a distinct (usually discontinuous and transient) dental lamina, but also in the absence of a successional lamina, e.g. from the surface epithelium of the oropharynx or from the outer dental epithelium of a predecessor tooth. The relationship of a replacement tooth to its predecessor is closely related to whether replacement is the result of a prepattern or occurs on demand. As replacement teeth do not necessarily have the same molecular signature as first-generation teeth, the question of the actual trigger for tooth replacement is discussed. Much emphasis has been laid in the past on the potential role of epithelial stem cells in initiating tooth replacement. The outcome of such studies has been equivocal, possibly related to the taxa investigated, and the permanent or transient nature of the dental lamina. Alternatively, replacement may result from local proliferation of undifferentiated progenitors, stimulated by hitherto unknown, perhaps mesenchymal, factors. So far, the role of the neurovascular link in continuous tooth replacement has been poorly investigated, despite the presence of a rich vascularisation surrounding actinopterygian (as well as chondrichthyan) teeth and despite a complete arrest of tooth replacement after nerve resection. Lastly, tooth replacement is possibly co-opted as a process to expand the number of teeth in a dentition ontogenetically whilst conserving features of the primary dentition. That neither a dental lamina, nor stem cells appear to be required for tooth replacement places teleosts in an advantageous position as models for tooth regeneration in humans, where the dental lamina regresses and epithelial stem cells are considered lost.
- MeSH
- biologická evoluce MeSH
- ryby * fyziologie MeSH
- zuby * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The nematode Spinitectus notopteri Karve et Naik, 1951 was collected from two species of freshwater fish belonging to the family Notopteridae, namely Chitala ornata (Gray) and Notopterus notopterus (Pallas), at Khun Thale Swamp in Surat Thani province of southern Thailand. The overall prevalence of the parasite was found to be 88% (94 fish infected/106 fish examined). A higher prevalence was found in C. ornata (96%), while a higher intensity was noted for N. notopterus (117 parasites/fish). The most important morphological characters were the presence of cephalic and cuticular structures, precloacal ridges, and genital papillae. Specimens were genetically characterised using cox1 mtDNA. Morphological characteristics were most similar to Spinitectus petterae Boomker, 1993 from Clarias gariepinus (Burchell) in Africa, while the genetic data were dissimilar to all available data for the genus. Therefore, the identification of nematode specimens using a combination of morphological and molecular techniques is stressed. This study also presents the first molecular analysis of S. notopteri infecting Thai freshwater fish and a new geographical record for S. notopteri.
- MeSH
- fylogeneze MeSH
- hlístice klasifikace anatomie a histologie genetika izolace a purifikace MeSH
- infekce hlísticemi řádu Spirurida veterinární parazitologie epidemiologie MeSH
- nemoci ryb * parazitologie epidemiologie MeSH
- ryby parazitologie MeSH
- sladká voda * MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Thajsko MeSH
Pseudomonas mandelii SW-3, isolated from the Napahai plateau wetland, can survive in cold environments. The mechanisms underlying the survival of bacteria in low temperatures and high altitudes are not yet fully understood. In this study, the whole genome of SW-3 was sequenced to identify the genomic features that may contribute to survival in cold environments. The results showed that the genome size of strain SW-3 was 6,538,059 bp with a GC content of 59%. A total of 67 tRNAs, a 34,110 bp prophage sequence, and a large number of metabolic genes were found. Based on 16S rRNA gene phylogeny and average nucleotide identity analysis among P. mandelii, SW-3 was identified as a strain belonging to P. mandelii. In addition, we clarified the mechanisms by which SW-3 survived in a cold environment, providing a basis for further investigation of host-phage interaction. P. mandelii SW-3 showed stress resistance mechanisms, including glycogen and trehalose metabolic pathways, and antisense transcriptional silencing. Furthermore, cold shock proteins and glucose 6-phosphate dehydrogenase may play pivotal roles in facilitating adaptation to cold environmental conditions. The genome-wide analysis provided us with a deeper understanding of the cold-adapted bacterium.
- MeSH
- DNA bakterií genetika MeSH
- fylogeneze * MeSH
- fyziologická adaptace * genetika MeSH
- genom bakteriální * MeSH
- nízká teplota * MeSH
- profágy genetika MeSH
- Pseudomonas * genetika klasifikace MeSH
- RNA ribozomální 16S * genetika MeSH
- sekvenování celého genomu MeSH
- zastoupení bazí MeSH
- Publikační typ
- časopisecké články MeSH
- MeSH
- biologická evoluce * MeSH
- fyziologické jevy MeSH
- genomika MeSH
- lidé MeSH
- molekulární evoluce MeSH
- původ života MeSH
- vědomí MeSH
- život MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
- MeSH
- biologická evoluce MeSH
- buňky MeSH
- čití, cítění fyziologie MeSH
- kognice fyziologie MeSH
- lidé MeSH
- mozek fyziologie MeSH
- původ života MeSH
- uvědomování si MeSH
- vědomí * fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
Satellite DNAs (satDNAs) are abundant components of eukaryotic genomes, playing pivotal roles in chromosomal organization, genome stability, and evolution. Here, we combined cytogenetic and genomic methods to characterize the satDNAs in the genomes of Leptidea butterflies. Leptidea is characterized by the presence of a high heterochromatin content, large genomes, and extensive chromosomal reshuffling as well as the occurrence of cryptic species. We show that, in contrast to other Lepidoptera, satDNAs constitute a considerable proportion of Leptidea genomes, ranging between 4.11% and 11.05%. This amplification of satDNAs, together with the hyperactivity of transposable elements, contributes to the substantial genome expansion in Leptidea. Using chromosomal mapping, we show that, particularly LepSat01-100 and LepSat03-167 satDNAs, are preferentially localized in heterochromatin exhibiting variable distribution that may have contributed to the highly diverse karyotypes within the genus. The satDNAs also exhibit W-chromosome accumulation, suggesting their involvement in sex chromosome evolution. Our results provide insights into the dynamics of satDNAs in Lepidoptera genomes and highlight their role in genome expansion and chromosomal organization, which could influence the speciation process. The high proportion of repetitive DNAs in the genomes of Leptidea underscores the complex evolutionary dynamics revealing the interplay between repetitive DNAs and genomic architecture in the genus.
The family Phyllobacteriaceae is a heterogeneous assemblage of more than 146 species of bacteria assigned to its existing 18 genera. Phylogenetic analyses have shown great phylogenetic diversity and also suggested about incorrect classification of several species that need to be reassessed for their proper phylogenetic classification. However, almost 50% of the family members belong to the genus Mesorhizobium only, of which the majority are symbiotic nitrogen fixers associated with different legumes. Other major genera are Phyllobacterium, Nitratireductor, Aquamicrobium, and Aminobacter. Nitrogen-fixing, legume nodulating members are present in Aminobacter and Phyllobacterium as well. Aquamicrobium spp. can degrade environmental pollutants, like 2,4-dichlorophenol, 4-chloro-2-methylphenol, and 4-chlorophenol. Chelativorans, Pseudaminobacter, Aquibium, and Oricola are the other genera that contain multiple species having diverse metabolic capacities, the rest being single-membered genera isolated from varied environments. In addition, heavy metal and antibiotic resistance, chemolithoautotrophy, poly-β-hydroxybutyrate storage, cellulase production, etc., are the other notable characteristics of some of the family members. In this report, we have comprehensively reviewed each of the species of the family Phyllobacteriaceae in their eco-physiological aspects and found that the family is rich with ecologically and metabolically highly diverse bacteria having great potential for human welfare and environmental clean-up.
The synchronous research and analysis of total and active soil microbial communities can provide insight into how these communities are impacted by continuous cropping years and pathogen infection. The diversity of total and active bacteria in rhizospheric soil of 2-year-old and 3-year-old healthy and diseased Panax notoginseng can comprehensively reveal the bacterial response characteristics in continuous cropping practice. The results showed that 4916 operational taxonomic units (OTUs) were found in the rhizospheric soil bacterial community of P. notoginseng at the DNA level, but only 2773 OTUs were found at the RNA level. The rhizospheric environment had significant effects on the active and bacterial communities, as indicated by the number of OTUs, Shannon, Chao1, Faith's phylogenetic diversity (Faith's PD), and Simpson's diversity indexes. The DNA level can better show the difference in diversity level before and after infection with root rot. The bacterial Chao1 and Faith's PD diversity indexes of 2-year-old root rot-diseased P. notoginseng rhizospheric soil (D2) were higher than that of healthy plants, while the bacterial Shannon diversity index of 3-year-old root rot-diseased P. notoginseng rhizospheric soil (D3) was the lowest in the total bacteria. Principal coordinate analysis (PCoA) illustrated that the total bacterial species composition changed markedly after root rot disease. There were significant differences in the composition of active bacterial species between the 2-year and 3-year rhizospheres. In conclusion, the total and active edaphic rhizospheric bacterial communities could provide important opportunities to understand the responses of bacteria to continuous cropping of P. notoginseng.
- MeSH
- Bacteria * klasifikace genetika izolace a purifikace MeSH
- biodiverzita * MeSH
- DNA bakterií genetika MeSH
- fylogeneze * MeSH
- kořeny rostlin mikrobiologie MeSH
- nemoci rostlin mikrobiologie MeSH
- Panax notoginseng * mikrobiologie MeSH
- půda chemie MeSH
- půdní mikrobiologie * MeSH
- rhizosféra * MeSH
- RNA ribozomální 16S genetika MeSH
- Publikační typ
- časopisecké články MeSH
