The Arabidopsis monovalent cation:proton antiporter-1 (CPA1) family includes eight members, AtNHX1-8. AtNHX1 and AtNHX7/SOS1 have been well characterized as tonoplast and plasma membrane Na+/H+ antiporters, respectively. The proteins AtNHX2-6 have been phylogenetically linked to AtNHX1, while AtNHX8 appears to be related to AtNHX7/SOS1. Here we report functional characterization of AtNHX8. AtNHX8 T-DNA insertion mutants are hypersensitive to lithium ions (Li+) relative to wild-type plants, but not to the other metal ions such as sodium (Na+), potassium (K+) and caesium (Cs+). AtNHX8 overexpression in a triple-deletion yeast mutant AXT3 that exhibits defective Na+/Li+ transport specifically suppresses sensitivity to Li+, but does not affect Na+ sensitivity. Likewise, AtNHX8 overexpression complemented sensitivity to Li+, but not Na+, in sos1-1 mutant seedlings, and increased Li+ tolerance of both the sos1-1 mutant and wild-type seedlings. Results of Li+ and K+ measurement of loss-of-function and gain-of-function mutants indicate that AtNHX8 may be responsible for Li+ extrusion, and may be able to maintain K+ acquisition and intracellular ion homeostasis. Subcellular localization of the AtNHX8-enhanced green fluorescent protein (EGFP) fusion protein suggested that AtNHX8 protein is targeted to the plasma membrane. Taken together, our findings suggest that AtNHX8 encodes a putative plasma membrane Li+/H+ antiporter that functions in Li detoxification and ion homeostasis in Arabidopsis. 相似文献
Root nodule formation is controlled by plant hormones such as auxin. Auxin-repressed protein (ARP) genes have been identified in various plant species but their functions are not clear. We have isolated a full-length cDNA clone (EuNOD-ARP1) showing high sequence homology to previously identified ARP genes from root nodules of Elaeagnus umbellata. Genomic Southern hybridization showed that there are at least four ARP-related genes in the genome of E. umbellata. The cDNA clone encodes a polypeptide of 120 amino acid residues with no signal peptide or organelle-targeting signals, indicating that it is a cytosolic protein. Its cytosolic location was confirmed using Arabidopsis protoplasts expressing a EuNOD-ARP1:smGFP fusion protein. Northern hybridization showed that EuNOD-ARP1 expression was higher in root nodules than in leaves or uninoculated roots. Unlike the ARP genes of strawberry and black locust, which are negatively regulated by exogenous auxin, EuNOD-ARP1 expression is induced by auxin in leaf tissue of E. umbellata. In situ hybridization revealed that EuNOD-ARP1 is mainly expressed in the fixation zone of root nodules. 相似文献
Two novel strains of the Cytophaga-Flexibacter-Bacteroides (CFB) group, designated Gsoil 219" and Gsoil 2381, were isolated from soil of a ginseng field of Pocheon Province in Korea. Both strains were Gram-negative, aerobic, nonmotile, nonspore-forming, and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences indicated that both isolates belong to the genus Chitinophaga but were clearly separated from established species of this genus. The sequence similarities between strain Gsoil 219T and type strains of the established species and between strain Gsoil 238T and type strains of the established species ranged from 91.4 to 94.7% and 91.6 to 94.2%, respectively. Phenotypic and chemotaxonomic data (major menaquinone, MK-7; major fatty acids, iso-C15:0 and C(16:1) omega5c; major hydroxy fatty acid, iso-C(17:0) 3-OH; major polyamine, homospermidine) supported the affiliation of both strains Gsoil 219T and Gsoil 238T to the genus Chitinophaga. Furthermore, the results of physiological and biochemical tests allowed genotypic and phenotypic differentiation of both strains from the other validated Chitinophaga species. Therefore, the two isolates represent two novel species, for which the name Chitinophaga soli sp. nov. (type strain, Gsoil 219T=KCTC 12650T=DSM 18093T) and Chitinophaga terrae sp. nov. (type strain, Gsoil 238T=KCTC 12651T=DSM 18078T) are proposed. 相似文献
We recently identified multivesicular bodies (MVBs) as prevacuolar compartments (PVCs) in the secretory and endocytic pathways to the lytic vacuole in tobacco (Nicotiana tabacum) BY-2 cells. Secretory carrier membrane proteins (SCAMPs) are post-Golgi, integral membrane proteins mediating endocytosis in animal cells. To define the endocytic pathway in plants, we cloned the rice (Oryza sativa) homolog of animal SCAMP1 and generated transgenic tobacco BY-2 cells expressing yellow fluorescent protein (YFP)-SCAMP1 or SCAMP1-YFP fusions. Confocal immunofluorescence and immunogold electron microscopy studies demonstrated that YFP-SCAMP1 fusions and native SCAMP1 localize to the plasma membrane and mobile structures in the cytoplasm of transgenic BY-2 cells. Drug treatments and confocal immunofluorescence studies demonstrated that the punctate cytosolic organelles labeled by YFP-SCAMP1 or SCAMP1 were distinct from the Golgi apparatus and PVCs. SCAMP1-labeled organelles may represent an early endosome because the internalized endocytic markers FM4-64 and AM4-64 reached these organelles before PVCs. In addition, wortmannin caused the redistribution of SCAMP1 from the early endosomes to PVCs, probably as a result of fusions between the two compartments. Immunogold electron microscopy with high-pressure frozen/freeze-substituted samples identified the SCAMP1-positive organelles as tubular-vesicular structures at the trans-Golgi with clathrin coats. These early endosomal compartments resemble the previously described partially coated reticulum and trans-Golgi network in plant cells. 相似文献
The aim of the study was to investigate the sensitivity of AHH-1 human lymphoblastoid cells to radiation and its relevance to intracellular events, specifically alteration in cellular energy-producing systems. AHH-1 human lymphoblastoid cells were irradiated with 6 Gy of gamma radiation, and then were collected at the indicated time points. Parallel studies were conducted to assess the effects of radiation on the cell proliferation and apoptotic index. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) production were monitored. A marked decrease of cell viability was observed as early as 12 h postirradiation and fraction of apoptotic cells was highest at 24 h. Intracellular ROS generation measured with 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) appeared to be highest as early as 30 min postirradiation and resumed to normal level at 6 h. Unexpectedly, the fluorescence intensity of Rhodamine 123 for measuring MMP did not change during the first 3h after radiation and exhibited an aberrant increase at 6 h. The results suggest that AHH-1 cells are sensitive to radiation-induced apoptosis and ROS generation is an early phase in the apoptosis process. Moreover, the results might cast doubts on those studies using Rhodamine 123 which hypothesized that the fall in MMP is one of the early events of apoptosis. 相似文献
Asian elephant is large herbivorous animal with elongated hindgut. To explore fecal microbial community composition with various ages, sex and diets, and their role in plant biomass degrading and nutrition conversation. We generated 119 Gb by metagenome sequencing from 10 different individual feces and identified 5.3 million non-redundant genes. The comprehensive analysis established that the Bacteroidetes, Firmicutes and Proteobacteria constituted the most dominant phyla in overall fecal samples. In different individuals, the alpha diversity of the fecal microbiota in female was lower than male, and the alpha diversity of the fecal microbiota in older was higher than younger, and the fecal microbial diversity was the most complex in wild elephant. But the predominant population compositions were similar to each other. Moreover, the newborn infant elephant feces assembled and maintained a diverse but host-specific fecal microbial population. The discovery speculated that Asian elephant maybe have start to building microbial populations before birth. Meanwhile, these results illustrated that host phylogeny, diets, ages and sex are significant factors for fecal microbial community composition. Therefore, we put forward the process of Asian elephant fecal microbial community composition that the dominant populations were built first under the guidance of phylogeny, and then shaped gradually a unique and flexible gut microbial community structure under the influences of diet, age and sex. This study found also that the Bacteroidetes were presumably the main drivers of plant fiber-degradation. A large of secondary metabolite biosynthetic gene clusters, and genes related to enediyne biosynthesis were found and showed that the Asian elephant fecal microbiome harbored a diverse and abundant genetic resource. A picture of antibiotic resistance genes (ARGs) reservoirs of fecal microbiota in Asian elephants was provided. Surprisingly, there was such wide range of ARGs in newborn infant elephant. Further strengthening our speculation that the fetus of Asian elephant has colonized prototypical fecal microbiota before birth. However, it is necessary to point out that the data give a first inside into the gut microbiota of Asian elephants but too few individuals were studied to draw general conclusions for differences among wild and captured elephants, female and male or different ages. Further studies are required. Additionally, the cultured actinomycetes from Asian elephant feces also were investigated, which the feces of Asian elephants could be an important source of actinomycetes.