RESUMO
The maintenance of germ cells is critical for the prosperity of offspring. The amount of food consumption is known to be closely related to reproduction, i.e., the number of eggs decreases under calorie-restricted conditions in various organisms. Previous studies in Caenorhabditis elegans have reported that calorie restriction reduces the number of eggs and the reduction can be rescued by methionine. However, the effect of methionine on the reproductive process has not been fully understood. In this study, to assess the gonadal function of methionine metabolism, we firstly demonstrated that a depletion in dietary methionine resulted in reduced levels of S-adenosyl-l-methionine (SAM) and S-adenosyl homocysteine (SAH) in wild-type N2, but not in glp-1 mutants, which possess only a few germ cells. Second, we found no recovery in egg numbers upon methionine administration in SAM synthase (sams)-1 mutants. Furthermore, a reduced number of proliferative zone nuclei exhibited in the sams-1 mutants was not rescued via methionine. Thus, our results have shown that dietary methionine is required for the normal establishment of both the germline progenitor pool and fecundity, mediated by sams-1.
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The causes and consequences of sex-ratio dynamics constitutes a pivotal subject in evolutionary biology1. Under conditions of evolutionary equilibrium, the male-to-female ratio tends to be approximately 1:1; however, this equilibrium is susceptible to distortion by selfish genetic elements exemplified by driving sex chromosomes and cytoplasmic elements2,3. Although previous studies have documented instances of these genetic elements distorting the sex ratio, studies specifically tracking the process with which these distorters spread within populations, leading to a transition from balanced parity to a skewed, female-biased state, are notably lacking. Herein, we present compelling evidence documenting the rapid spread of the cytoplasmic endosymbiont Wolbachia within a localized population of the pierid butterfly Eurema hecabe (Figure 1A). This spread resulted in a shift in the sex ratio from near parity to an exceedingly skewed state overwhelmingly biased toward females, reaching 93.1% within a remarkably brief period of 4 years.
Assuntos
Borboletas , Razão de Masculinidade , Simbiose , Wolbachia , Animais , Wolbachia/fisiologia , Wolbachia/genética , Borboletas/microbiologia , Borboletas/fisiologia , Borboletas/genética , Feminino , MasculinoRESUMO
Wolbachia, cytoplasmically inherited endosymbionts of arthropods, are known to hijack their host reproduction in various ways to increase their own vertical transmission. This may lead to the selective sweep of associated mitochondria, which can have a large impact on the evolution of mitochondrial lineages. In Japan, two different Wolbacahia strains (wCI and wFem) are found in two sister species of pierid butterflies, Eurema mandarina and Eurema hecabe. In both species, females infected with wCI (C females) produce offspring with a nearly 1:1 sex ratio, while females infected with both wCI and wFem (CF females) produce all-female offspring. Previous studies have suggested the historical occurrence of hybrid introgression in C individuals between the two species. Furthermore, hybrid introgression in CF individuals is suggested by the distinct mitochondrial lineages between C females and CF females of E. mandarina. In this study, we performed phylogenetic analyses based on nuclear DNA and mitochondrial DNA markers of E. hecabe with previously published data on E. mandarina. We found that the nuclear DNA of this species significantly diverged from that of E. mandarina. By contrast, mitochondrial DNA haplotypes comprised two clades, mostly reflecting Wolbachia infection status rather than the individual species. Collectively, our results support the previously suggested occurrence of two independent historical events wherein the cytoplasms of CF females and C females moved between E. hecabe and E. mandarina through hybrid introgression.
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OBJECTIVE: In insects, closely related species are often difficult or impossible to distinguish solely by morphological traits. Mitochondrial DNA (mtDNA) markers are often useful and reliable for distinguishing closely related species. However, useful mtDNA markers can be unavailable, particularly when such species pairs experienced hybrid introgression in the past. Although polymorphic nuclear DNA markers would be necessary to distinguish such species pairs, recombination, multiple copies, and slower mutation rates of the nuclear DNA compared with those of mtDNA often make it challenging. The objective of this study was to develop a multiplex polymerase chain reaction that can reliably amplify and distinguish the Tpi sequences of Eurema mandarina and Eurema hecabe. RESULTS: We successfully analyzed the nucleotide sequences of the Z chromosome-linked triose phosphate isomerase (Tpi) gene to develop a multiplex polymerase chain reaction (PCR) that amplified ca. 120-bp products for E. mandarina and ca. 375-bp products for E. hecabe. We suggest that multiplex PCR using Tpi with appropriately designed primers can be used to accurately and reliably distinguish between other closely related Lepidoptera species.
Assuntos
Borboletas/genética , Reação em Cadeia da Polimerase Multiplex , Triose-Fosfato Isomerase/genética , Animais , Feminino , Masculino , Especificidade da EspécieRESUMO
The tricarboxylic acid (TCA) cycle (or citric acid cycle) is responsible for the complete oxidation of acetyl-CoA and formation of intermediates required for ATP production and other anabolic pathways, such as amino acid synthesis. Here, we uncovered an additional mechanism that may help explain the essential role of the TCA cycle in the early embryogenesis of Caenorhabditis elegans. We found that knockdown of citrate synthase (cts-1), the initial and rate-limiting enzyme of the TCA cycle, results in early embryonic arrest, but that this phenotype is not because of ATP and amino acid depletions. As a possible alternative mechanism explaining this developmental deficiency, we observed that cts-1 RNAi embryos had elevated levels of intracellular acetyl-CoA, the starting metabolite of the TCA cycle. Of note, we further discovered that these embryos exhibit hyperacetylation of mitochondrial proteins. We found that supplementation with acetylase-inhibiting polyamines, including spermidine and putrescine, counteracted the protein hyperacetylation and developmental arrest in the cts-1 RNAi embryos. Contrary to the hypothesis that spermidine acts as an acetyl sink for elevated acetyl-CoA, the levels of three forms of acetylspermidine, N1-acetylspermidine, N8-acetylspermidine, and N1,N8-diacetylspermidine, were not significantly increased in embryos treated with exogenous spermidine. Instead, we demonstrated that the mitochondrial deacetylase sirtuin 4 (encoded by the sir-2.2 gene) is required for spermidine's suppression of protein hyperacetylation and developmental arrest in the cts-1 RNAi embryos. Taken together, these results suggest the possibility that during early embryogenesis, acetyl-CoA consumption by the TCA cycle in C. elegans prevents protein hyperacetylation and thereby protects mitochondrial function.
Assuntos
Caenorhabditis elegans/embriologia , Caenorhabditis elegans/metabolismo , Ciclo do Ácido Cítrico , Desenvolvimento Embrionário , Proteínas Mitocondriais/metabolismo , Acetilação , Trifosfato de Adenosina/metabolismo , Animais , Ácido Aspártico/metabolismo , Caenorhabditis elegans/citologia , Caenorhabditis elegans/genética , Citrato (si)-Sintase/deficiência , Citrato (si)-Sintase/genética , Ácido Cítrico/metabolismo , Ácido Glutâmico/metabolismo , Espaço Intracelular/metabolismo , Fatores de TempoRESUMO
RNAs are post-transcriptionally modified in all kingdoms of life. Of these modifications, base methylations are highly conserved in eukaryote ribosomal RNA (rRNA). Recently, rRNA processing protein 8 (Rrp8) and nucleomethylin (NML) were identified as factors of N1-methyladenosine (m1A) modification in yeast 25 S and mammalian 28 S rRNA, respectively. However, m1A modification of rRNA is still poorly understood in Caenorhabditis elegans (C. elegans). Here, using the liquid chromatography/tandem mass spectrometry analysis and RNA immunoprecipitation assay, we have identified that the m1A modification is located around position 674 (A674) of 26 S rRNA in C. elegans. Furthermore, quantitative PCR-based analysis revealed that T07A9.8, a C. elegans homolog of yeast Rrp8 and human NML, is responsible for m1A modification at A674 of 26 S rRNA. This m1A modification site in C. elegans corresponds to those in yeast 25 S rRNA and human 28 S rRNA. Intriguingly, T07A9.8 is not associated with pre-rRNA transcription under normal nutrient conditions. Since the m1A modification of 26 S rRNA requires T07A9.8 in C. elegans, we designated the gene as rRNA adenine methyltransferase-1 (rram-1).
Assuntos
Adenina/metabolismo , Caenorhabditis elegans/genética , RNA Ribossômico/metabolismo , DNA Metiltransferases Sítio Específica (Adenina-Específica)/metabolismo , Animais , Caenorhabditis elegans/enzimologia , Caenorhabditis elegans/metabolismo , Metilação , RNA Ribossômico/química , Reação em Cadeia da Polimerase Via Transcriptase Reversa , DNA Metiltransferases Sítio Específica (Adenina-Específica)/genéticaRESUMO
Maternally inherited Wolbachia endosymbionts manipulate arthropod reproduction in various ways. In the butterfly Eurema mandarina, a cytoplasmic incompatibility-inducing Wolbachia strain wCI and the associated mtDNA haplotypes are known to originate from the sister species Eurema hecabe, which offered a good case study for microbe-mediated hybrid introgression. Besides wCI, some females with the Z0 karyotype harbour a distinct Wolbachia strain wFem, which causes all-female production by meiotic drive and feminization. We report that a considerable proportion of E. mandarina females (65.7%) were infected with both wCI and wFem (CF) on Tanegashima Island. While females singly infected with wCI (C) produced offspring at a 1 : 1 sex ratio, CF females produced only females. Although Z-linked sequence polymorphism showed no signs of divergence between C and CF females, mtDNA split into two discrete clades; one consisted of C females and the other CF females, both of which formed a clade with E. hecabe but not with uninfected E. mandarina This suggests that CF matrilines also, but independently, experienced a selective sweep after hybrid introgression from E. hecabe Distinct evolutionary forces were suggested to have caused C and CF matrilines to diverge, which would be irreversible because of the particular phenotype of wFem.
Assuntos
Wolbachia , Animais , Borboletas , DNA Mitocondrial , Feminino , Feminização , Masculino , Mitocôndrias , Razão de MasculinidadeRESUMO
Wolbachia is a maternally inherited ubiquitous endosymbiotic bacterium of arthropods that displays a diverse repertoire of host reproductive manipulations. For the first time, we demonstrate that Wolbachia manipulates sex chromosome inheritance in a sexually reproducing insect. Eurema mandarina butterfly females on Tanegashima Island, Japan, are infected with the wFem Wolbachia strain and produce all-female offspring, while antibiotic treatment results in male offspring. Fluorescence in situ hybridization (FISH) revealed that wFem-positive and wFem-negative females have Z0 and WZ sex chromosome sets, respectively, demonstrating the predicted absence of the W chromosome in wFem-infected lineages. Genomic quantitative polymerase chain reaction (qPCR) analysis showed that wFem-positive females lay only Z0 eggs that carry a paternal Z, whereas females from lineages that are naturally wFem-negative lay both WZ and ZZ eggs. In contrast, antibiotic treatment of adult wFem females resulted in the production of Z0 and ZZ eggs, suggesting that this Wolbachia strain can disrupt the maternal inheritance of Z chromosomes. Moreover, most male offspring produced by antibiotic-treated wFem females had a ZZ karyotype, implying reduced survival of Z0 individuals in the absence of feminizing effects of Wolbachia. Antibiotic treatment of wFem-infected larvae induced male-specific splicing of the doublesex (dsx) gene transcript, causing an intersex phenotype. Thus, the absence of the female-determining W chromosome in Z0 individuals is functionally compensated by Wolbachia-mediated conversion of sex determination. We discuss how Wolbachia may manipulate the host chromosome inheritance and that Wolbachia may have acquired this coordinated dual mode of reproductive manipulation first by the evolution of female-determining function and then cytoplasmically induced disruption of sex chromosome inheritance.
RESUMO
The crystal and defect structures of coarse-grained crystals of La(2/3-x)Li(3x)TiO3 grown from the melt by the Tammann-Stöber method were studied by transmission electron microscopy and powder X-ray diffraction. The as-grown crystals of La(2/3-x)Li(3x)TiO3 have a Li-poor composition of La(0.57)Li(0.29)TiO3 and a diagonal-type unit cell of 2(1/2)a(p) x 2(1/2)a(p) x 2a(p) with the tetragonal symmetry [space group: P4/nbm (#125)] due to both the La-cation ordering and the tilting of TiO6 octahedra. The secondary La2Ti2O7 phase precipitates in the form of plates in the La(2/3-x)Li(3x)TiO3 phase with the orientation relationships of 001(p)//[100](La2Ti2O7) and {110}(p)//(001)(La2Ti2O7), which may cause detrimental effects to ionic conductivity.