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The African grass or Nile rat (NR) (Arvicanthis niloticus) is a herbivorous diurnal rodent which is used as a biological model for research on type 2 diabetes mellitus (T2DM) and the circadian rhythm. Similar to humans, male NRs develop T2DM with high-carbohydrate diets. The NR thus provides a unique opportunity to identify the nutritional and underlying genetic factors that characterise human T2DM, as well as the effects of potential anti-diabetic phytochemicals such as Water-Soluble Palm Fruit Extract. Whole genome sequencing (WGS) could help identify possible genetic causes why NRs spontaneously develop T2DM in captivity. In this study, we performed WGS on a hepatic deoxyribonucleic acid (DNA) sample isolated from a male NR using PacBio high-fidelity long-read sequencing. The WGS data obtained were then de novo assembled and annotated using PacBio HiFi isoform sequencing (Iso-Seq) data as well as previous Illumina RNA sequencing (RNA-Seq) data. Genes related to insulin and circadian rhythm pathways were present in the NR genome, similar to orthologues in the rat, mouse and human genomes. T2DM development in the NR is thus most likely not attributable to structural differences in these genes when compared to other biological models. Further studies are warranted to gain additional insights on the genetic-environmental factors which underlie the genetic permissiveness of NRs to develop T2DM.

The fluctuation experiment, devised by Luria and Delbrück in 1943, remains the method of choice for measuring microbial mutation rates in the laboratory. While most inference problems commonly encountered in a fluctuation experiment can be tackled by existing standard algorithms, investigators from time to time run into nonstandard problems not amenable to any existing algorithms. A major obstacle to solving these nonstandard problems is the construction of confidence intervals for mutation rates. This note describes methods for two important categories of nonstandard problems, namely, pooling data from separate experiments and analyzing grouped mutant count data, focusing on the construction of likelihood ratio confidence intervals. In addition to illustrative examples using real-world data, simulation results are presented to help assess the proposed methods.

There has been a continuous interest in understanding the patterns of genetic diversity in natural populations because of the role of intraspecific genetic diversity as the basis of all evolutionary change and thus, its potential effects on population persistence when facing environmental changes. Here, we provided the first description of genetic diversity distribution and population structure of Anacardium occidentale L. (cashew) from the Brazilian Cerrado, one of the most economically important tropical crops in the world. We applied Bayesian clustering approaches (STRUCTURE and POPS) that allow predicting the effects of future climatic changes on the population genetic structure of A. occidentale. We identified distinct genetic groups corresponding to the southwestern, central, and northern regions of the species' range. The characterized genetic clusters will disappear under future climate change scenarios, leading to a homogenization of genetic variability across the landscape. Our findings suggest a high likelihood for the loss of genetic diversity, which in turn will reduce the evolutionary potential of the species to cope with predicted future climatic changes. Results from this study may help develop management strategies to conserve the genetic diversity and structure of natural cashew populations.

Identifying homologs is an important process in the analysis of genetic patterns underlying traits and evolutionary relationships among species. Analysis of gene families is often used to form and support hypotheses on genetic patterns such as gene presence, absence, or functional divergence which underlie traits examined in functional studies. These analyses often require precise identification of all members in a targeted gene family. Manual pipelines where homology search and orthology assignment tools are used separately are the most common approach for identifying small gene families where accurate identification of all members is important. The ability to curate sequences between steps in manual pipelines allows for simple and precise identification of all possible gene family members. However, the validity of such manual pipeline analyses is often decreased by inappropriate approaches to homology searches including too relaxed or stringent statistical thresholds, inappropriate query sequences, homology classification based on sequence similarity alone, and low-quality proteome or genome sequences. In this article, we propose several approaches to mitigate these issues and allow for precise identification of gene family members and support for hypotheses linking genetic patterns to functional traits.

The Drosophila GAGA-factor encoded by the Trithorax-like (Trl) gene is DNA-binding protein with unusually wide range of applications in diverse cell contexts. In Drosophila spermatogenesis, reduced GAGA expression caused by Trl mutations induces mass autophagy leading to germ cell death. In this work, we investigated the contribution of mitochondrial abnormalities to autophagic germ cell death in Trl gene mutants. Using a cytological approach, in combination with an analysis of high-throughput RNA sequencing (RNA-seq) data, we demonstrated that the GAGA deficiency led to considerable defects in mitochondrial ultrastructure, by causing misregulation of GAGA target genes encoding essential components of mitochondrial molecular machinery. Mitochondrial anomalies induced excessive production of reactive oxygen species and their release into the cytoplasm, thereby provoking oxidative stress. Changes in transcription levels of some GAGA-independent genes in the Trl mutants indicated that testis cells experience ATP deficiency and metabolic aberrations, that may trigger extensive autophagy progressing to cell death.

The light-dark cycle significantly impacts the growth and development of animals. Mantis shrimps (Oratosquilla oratoria) receive light through their complex photoreceptors. To reveal the adaptive expression mechanism of the mantis shrimp induced in a dark environment, we performed comparative transcriptome analysis with O. oratoria cultured in a light environment (Oo-L) as the control group and O. oratoria cultured in a dark environment (Oo-D) as the experimental group. In the screening of differentially expressed genes (DEGs) between the Oo-L and Oo-D groups, a total of 88 DEGs with |log2FC| > 1 and FDR < 0.05 were identified, of which 78 were upregulated and 10 were downregulated. Then, FBP1 and Pepck were downregulated in the gluconeogenesis pathway, and MKNK2 was upregulated in the MAPK classical pathway, which promoted cell proliferation and differentiation, indicating that the activity of mantis shrimp was slowed and the metabolic rate decreases in the dark environment. As a result, the energy was saved for its growth and development. At the same time, we performed gene set enrichment analysis (GSEA) on all DEGs. In the KEGG pathway analysis, each metabolic pathway in the dark environment showed a slowing trend. GO was enriched in biological processes such as eye development, sensory perception and sensory organ development. The study showed that mantis shrimp slowed down metabolism in the dark, while the role of sensory organs prominent. It provides important information for further understanding the energy metabolism and has great significance to study the physiology of mantis shrimp in dark environment.

Ionotropic glutamate receptors are ligand-gated nonselective cation channels that mediate neurotransmission in the central nervous system of animals. Plants possess homologous proteins called glutamate receptor-like channels (GLRs) which are involved in vital physiological processes including seed germination, long-distance signaling, chemotaxis, Ca²⁺ signaling etc. Till now, a comprehensive genome-wide analysis of the GLR gene family members in different economically important species of Brassica is missing. Considering the origin of allotetraploid Brassica napus from the hybridization between the diploid Brassica oleracea and Brassica rapa, we have identified 11, 27 and 65 GLR genes in B. oleracea, B. rapa and B. napus, respectively showing an expansion of this gene family in B. napus. Chromosomal locations revealed several tandemly duplicated GLR genes in all the three species. Moreover, the gene family expanded in B. napus after allopolyploidization. The phylogenetic analysis showed that the 103 GLRs are classified into three main groups. The exon-intron structures of these genes are not very conserved and showed wide variation in intron numbers. However, protein sequences are much conserved as shown by the presence of ten short amino acid sequence motifs. Predicted cis-acting elements in 1 kb promoters of GLR genes are mainly involved in light, stress and hormone responses. RNA-seq analysis showed that in B. oleracea and B. rapa, some GLRs are more tissue specific than others. In B. napus, some GLRs are downregulated under cold stress, while others are upregulated. In summary, this bioinformatic study of the GLR gene family of the three Brassica species provides evidence for the expansion of this gene family in B. napus and also provided useful information for in-depth studies of their biological functions in Brassica.

The scarlet macaw, Ara macao, is a neotropical parrot that contains two described subspecies with broadly discrete geographical distributions. One subspecies, A. m. macao, is found from South America north into southwestern Costa Rica, while the second subspecies, A. m. cyanoptera, is found from eastern Costa Rica north into central Mexico. Our previous research using mitochondrial data to examine phylogeographical divergence across the collective range of these two subspecies concluded that they represent distinct evolutionary entities, with minimal contemporary hybridization between them. Here we further examine phylogenetic relationships and patterns of genetic variation between these two subspecies using a dataset of genetic markers derived from their nuclear genomes. Our analyses show clear nuclear divergence between A. m. macao and A. m. cyanoptera in Central America. Collectively however, samples from this region appear genetically more similar to one another than they do to the examined South American (Brazilian) A. m. macao sample. This observation contradicts our previous assessments based on mitochondrial DNA analyses that A. m. macao in Central and South America represent a single phylogeographical group that is evolutionarily distinct from Central American A. m. cyanoptera. Nonetheless, in agreement with our previous findings, ongoing genetic exchange between the two subspecies appears limited. Rather, our analyses indicate that incomplete lineage sorting is the best supported explanation for cytonuclear discordance within these parrots. High-altitude regions in Central America may act as a reproductive barrier, limiting contemporary hybridization between A. m. macao and A. m. cyanoptera. The phylogeographic complexities of scarlet macaw taxa in this region highlight the need for additional evolutionary examinations of these populations.

In the Neotropical region, one of the most diverse families of freshwater fishes is the monophyletic Serrasalmidae. Karyotypically, the family shows high diversity in chromosome numbers (2n = 54 to 64). However, little is discussed about whether the chromosomal changes are associated with cladogenetic events within this family. In the present study, we evaluated the role of chromosomal changes in the evolutionary diversification of Serrasalmidae. Our phylogenetic sampling included 36 species and revealed three main clades. The ancestral chromosome number reconstruction revealed the basic number 2n = 54 and a high frequency of ascending dysploid events in the most derived lineages. Our biogeographic reconstruction suggests an Amazonian origin of the family at 48-38 Mya, with independent colonization of other basins between 15 and 8 Mya. We did not find specific chromosomal changes or increased diversification rates correlated with the colonization of a new environment. On the other hand, an increase in the diversification rate was detected involving the genus Serrasalmus and Pygocentrus in the Miocene, correlated with the stasis of 2n = 60. Our data demonstrate that chromosomal rearrangements might have played an important evolutionary role in major cladogenetic events in Serrasalmidae, revealing them as a possible evolutionary driver in their diversification.