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991.
Ion dynamics are important for cell nutrition and growth in fungi and plants. Here, the focus is on the relationship between the hyphal H(+) fluxes and the control of presymbiotic growth and host recognition by arbuscular mycorrhizal (AM) fungi. Fluxes of H(+) around azygopores and along lateral hyphae of Gigaspora margarita during presymbiotic growth, and their regulation by phosphate (P) and sucrose (Suc), were analyzed with an H(+)-specific vibrating probe. Changes in hyphal H(+) fluxes were followed after induction by root exudates (RE) or by the presence Trifolium repens roots. Differential sensitivity to P-type ATPase inhibitors (orthovanadate or erythrosin B) suggests an asymmetric distribution or activation of H(+)-pump isoforms along the hyphae of the AM fungi. Concentration of P and Suc affected the hyphal H(+) fluxes and growth rate. However, further increases in H+ efflux and growth rate were observed when the fungus was growing close to clover roots or pretreated with RE. The H(+) flux data correlate with those from polarized hyphal growth analyses, suggesting that spatial and temporal alterations of the hyphal H(+)fluxes are regulated by nutrient availability and might underlie a pH signaling elicitation by host RE during the early events of the AM symbiosis. 相似文献
992.
* Cadmium (Cd) stress increases cell metabolic demand for sulfur, reducing equivalents, and carbon skeletons, to sustain phytochelatin biosynthesis for Cd detoxification. In this condition the induction of potentially acidifying anaplerotic metabolism in root tissues may be expected. For these reasons the effects of Cd accumulation on anaplerotic metabolism, glycolysis, and cell pH control mechanisms were investigated in maize (Zea mays) roots. * The study compared root apical segments, excised from plants grown for 24 h in a nutrient solution supplemented, or not, with 10 microM CdCl(2), using physiological, biochemical and (31)P-nuclear magnetic resonance (NMR) approaches. * Cadmium exposure resulted in a significant decrease in both cytosolic and vacuolar pH of root cells and in a concomitant increase in the carbon fluxes through anaplerotic metabolism leading to malate biosynthesis, as suggested by changes in dark CO2 fixation, metabolite levels and enzyme activities along glycolysis, and mitochondrial alternative respiration capacity. This scenario was accompanied by a decrease in the net H(+) efflux from the roots, probably related to changes in plasma membrane permeability. * It is concluded that anaplerotic metabolism triggered by Cd detoxification processes might lead to an imbalance in H(+) production and consumption, and then to cell acidosis. 相似文献
993.
Kasraie S Houshmand M Banoei MM Ahari SE Panahi MS Shariati P Bahar M Moin M 《Cellular and molecular neurobiology》2008,28(7):933-938
Huntington disease (HD) is a genetically dominant condition caused by expanded CAG repeats which code for glutamine in the
HD gene product, huntingtin. Huntingtin is expressed in almost all tissues, so abnormalities outside the brain can also be
expected. Involvement of nuclei and mitochondria in HD pathophysiology has been suggested. In fact mitochondrial dysfunction
is reported in brains of patients suffering from HD. The tRNA gene mutations are one of hot spots that can cause mitochondrial
disorders. In this study, possible mitochondrial DNA (mtDNA) damage was evaluated by screening for mutations in the tRNAleu/lys and ATPase 6 genes of 20 patients with HD, using PCR and automated DNA sequencing. Mutations including an A8656G mutation
in one patient were observed, which may be causal to the disease. Understanding the role of mitochondria in the pathogenesis
of neurodegenerative diseases could potentially be important for the development of therapeutic strategies in HD. 相似文献
994.
995.
白鱼线粒体DNA控制区结构和种群遗传多样性分析 总被引:1,自引:0,他引:1
用特异性引物对白鱼(Anabarilius grahami)DNA进行PCR扩增,获得了白鱼线粒体DNA控制区基因全序列(930bp)。控制区T、C、A和G碱基组成为29.8%、22.5%、33.0%和14.7%。对照其他已报道的鱼类控制区结构,对白鱼控制区结构进行了分析,识别了其终止序列区、中央保守区和保守序列区,找到了终止相关的序列TAS以及保守序列(CSB-F、CSB-D、CSB-1、CSB-2、CSB-3)。同时运用DNA分析软件对白鱼一个驯养种群(中国科学院昆明动物研究所珍稀鱼类繁育中心)及两个自然地理种群(江川县明星鱼洞、江川县牛摩村)进行了遗传多样性分析。结果显示:两个自然种群存在较强基因交流,未出现遗传分化;人工驯养种群遗传多样性最高,种群复壮程度较好。 相似文献
996.
Vítor Sousa Filipa Penha Maria J. Collares-Pereira Lounès Chikhi Maria M. Coelho 《Conservation Genetics》2008,9(4):791-805
The endemic and critically endangered cyprinid Chondrostoma lusitanicum has a very restricted distribution range. In order to estimate genetic diversity, characterize population structure and infer
the demographic history, we examined six microsatellite loci and cytochrome b (mtDNA) sequences from samples taken throughout C. lusitanicum’s geographical range. Estimates of genetic diversity were low in all samples (average He < 0.35). The microsatellite data
pointed to a major difference between northern (Samarra and Tejo drainages) and southern (Sado and Sines drainages) samples.
This separation was not so clear with mtDNA, since one sample from the Tejo drainage grouped with the southern samples. This
could be related with ancestral polymorphism or with admixture events between northern and southern sites during the late
Pleistocene. Nevertheless, both markers indicate high levels of population differentiation in the north (for microsatellites
F
ST > 0.23; and for mtDNA ΦST > 0.74) and lower levels in the south (F
ST < 0.05; ΦST < 0.40). With microsatellites we detected strong signals of a recent population decrease in effective size, by more than
one order of magnitude, starting in the last centuries. This is consistent with field observations reporting a severe anthropogenic-driven
population decline in the last decades. On the contrary mtDNA suggested a much older expansion. Overall, these results suggest
that the distribution of genetic diversity in C. lusitanicum is the result of both ancient events related with drainage system formation, and recent human activities. The potential effect
of population substructure generating genetic patterns similar to a population decrease is discussed, as well as the implications
of these results for the conservation of C. lusitanicum.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
997.
Hayley A. Lawrence Graeme A. Taylor Craig D. Millar David M. Lambert 《Conservation Genetics》2008,9(5):1293-1301
Interpreting the levels of genetic diversity in organisms with diverse life and population histories can be difficult. The
processes and mechanisms regulating this diversity are complex and still poorly understood. However, endangered species typically
have low genetic variation as a consequence of the effects of genetic drift in small populations. In this study we examine
genetic variation in the critically endangered Chatham Island Taiko (Tchaik, Pterodroma magentae), one of the world’s rarest seabirds. The Taiko has a very small population size of between 120 and 150 individuals, including
just 8–15 breeding pairs. We report surprisingly high mitochondrial and nuclear genetic diversity in this critically endangered
long-lived species. We hypothesise that the present Taiko population has retained a significant proportion of its past genetic
diversity. However, it is also possible that undiscovered birds are breeding in unknown areas, which could increase the population
size estimate. Importantly, from a conservation perspective, we show that the high level of variation is unlikely to be maintained
in the future since chicks currently being born have only a limited number of the mitochondrial DNA haplotypes found in adults.
Reduced genetic variation will mean that our ability to infer past events and the population history of Taiko using genetics
could soon be lost and the power to determine, for example, parentage and other close order relationships will be diminished.
Therefore, the maintenance of genetic diversity in future generations is an important consideration for conservation management
of the Taiko. 相似文献
998.
Aurel I. Lozan Michael T. Monaghan Karel Spitzer Josef Jaroš Martina Žurovcová Václav Brož 《Conservation Genetics》2008,9(6):1431-1437
Island-endemic species can be particularly vulnerable to alien invasion. There are many examples of introduced insect parasitoids
having a serious impact on endemic butterflies and moths. In 2006, a population of parasitic wasps was reared from larvae
of the Canary Island Large White butterfly (Pieris cheiranthi), an endemic inhabitant of laurel forests unique to the Canary Islands of Macaronesia. Parasitoids were tentatively identified
as Cotesia glomerata (Braconidae, Hymenoptera), a widely introduced agricultural bioagent. To corroborate this finding we sequenced 632 bp of
mitochondrial cox1 from parasitoids and hosts from La Palma and from the native range of C. glomerata in continental Europe. These were combined with GenBank sequences and a character-based, phylogenetic approach was used to
assess the species status of parasites and hosts. The La Palma parasitoid could unambiguously be assigned to C. glomerata under the criterion of diagnosibility with corroboration from multiple lines of evidence (DNA, morphology). We suggest that
this opportunistic, non-native parasitoid wasp will be a threat to P. cheiranthi and other endemic Canarian butterflies. Parasitoid populations were recorded from P. cheiranthi in marginal forest habitats but not in central forest areas, suggesting that comprehensive habitat conservation of the Canarian
laurel forests could prevent penetration of the alien parasitoid wasps and subsequent mortality of endemic butterfly populations. 相似文献
999.
Mutations in mitochondrial small subunit ribosomal proteins MRPS16 or MRPS22 cause severe, fatal respiratory chain dysfunction due to impaired translation of mitochondrial mRNAs. The loss of either MRPS16 or MRPS22 was accompanied by the loss of most of another small subunit protein MRPS11. However, MRPS2 was reduced only about 2-fold in patient fibroblasts. This observation suggests that the small ribosomal subunit is only partially able to assemble in these patients. Two large subunit ribosomal proteins, MRPL13 and MRPL15, were present in substantial amounts suggesting that the large ribosomal subunit is still present despite a non-functional small subunit. 相似文献
1000.
We have amplified two cDNAs, coding for creatine kinases (CKs), from the skeletal muscle of sperm whale Physeter macrocephalus by PCR, and cloned these cDNAs into pMAL plasmid. These are the first CK cDNA and deduced amino acid sequences from cetaceans
to be reported. One of the two amino acid sequences is a cytoplasmic, muscle-type isoform (MCK), while the other was identified
as a sarcomeric, mitochondrial isoform (sMiCK) that included a mitochondrial targeting peptide. The amino acid sequences of
sperm whale MCK and sMiCK showed 94–96% sequence identity with corresponding isoforms of mammalian CKs, and all of the key
residues necessary for CK function were conserved. The phylogenetic analyses of vertebrate CKs with three independent methods
(neighbor-joining, maximum-likelihood and Bayes) supported the clustering of sperm whale MCK with Bos and Sus MCKs, in agreement with the contemporary view that these groups are closely related. Sperm whale MCK and sMiCK were expressed
in Escherichia coli as a fusion protein with maltose-binding protein, and the kinetic constants (K
m, K
d and k
cat) were determined for the forward reaction. Comparison of kinetic constants with those of human and mouse CKs indicated that
sperm whale MCK has a comparable affinity for creatine (K
mCr = 9.38 mM) to that of human MCK, and the sMiCK has two times higher affinity for creatine than the human enzyme. Both the
MCK and sMiCK of sperm whale display a synergistic substrate binding (K
d
/K
m = 3.1–7.8) like those of other mammalian CKs. 相似文献