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91.
92.
Background
Severe cardiotoxicity is a documented, but very unusual side-effect of intravenous 5-fluorouracil therapy. The mechanism producing cardiotoxicity is poorly understood. 相似文献93.
Plant development is controlled by both endogenous genetic programs and responses to exogenous signals. Microarray experiments are being used to identify the genes involved in these developmental processes. Most of the analyses conducted to date have been conducted on whole organs. Although these studies have provided valuable information, they are limited by the composite nature of plant organs that consist of multiple cell types. Technical advances that have made it possible to study global patterns of gene expression in individual cell types promise to increase greatly the information revealed by microarray experiments. 相似文献
94.
Cytoplasmic regulation of the accumulation of nuclear-encoded proteins in the mitochondrial proteome of maize 总被引:10,自引:0,他引:10
Hochholdinger F Guo L Schnable PS 《The Plant journal : for cell and molecular biology》2004,37(2):199-208
Mitochondria from normal (NA)- and Texas (T)-cytoplasm maize (Zea mays L.) were purified from unpollinated ears via Percoll centrifugation. Approximately 300 mitochondrial proteins were resolved using two-dimensional (2-D) electrophoresis. The 197 most abundant proteins were analyzed by matrix-assisted laser desorption ionization time-of-flight (MALDI-ToF) mass spectrometry involving overlapping pH gradients (pH 4-7 and 6-9). Database searches identified 58 genes that encode 100 of these protein spots. Functions could be predicted for 38 of the 58 genes (66%). All but one of these genes are located in the nuclear genome. Thirteen per cent of the analyzed protein spots (25 out of 197) exhibited at least a threefold difference in accumulation between the mitochondrial proteomes of NA- or T-cytoplasm maize plants that had essentially identical nuclear genomes. As most of these proteins were nuclear-encoded, these findings demonstrate that the genotype of a mitochondrion can regulate the accumulation of the nuclear-encoded fraction of its proteome. About half (27 out of 58) of the maize mitochondrial proteins identified in this study were not recovered in previous analyses of the Arabidopsis and rice mitochondrial proteomes. 相似文献
95.
Mitochondrial aldehyde dehydrogenase activity is required for male fertility in maize 总被引:24,自引:0,他引:24 下载免费PDF全文
Some plant cytoplasms express novel mitochondrial genes that cause male sterility. Nuclear genes that disrupt the accumulation of the corresponding mitochondrial gene products can restore fertility to such plants. The Texas (T) cytoplasm mitochondrial genome of maize expresses a novel protein, URF13, which is necessary for T cytoplasm-induced male sterility. Working in concert, functional alleles of two nuclear genes, rf1 and rf2, can restore fertility to T cytoplasm plants. Rf1 alleles, but not Rf2 alleles, reduce the accumulation of URF13. Hence, Rf2 differs from typical nuclear restorers in that it does not alter the accumulation of the mitochondrial protein necessary for T cytoplasm-induced male sterility. This study established that the rf2 gene encodes a soluble protein that accumulates in the mitochondrial matrix. Three independent lines of evidence establish that the RF2 protein is an aldehyde dehydrogenase (ALDH). The finding that T cytoplasm plants that are homozygous for the rf2-R213 allele are male sterile but accumulate normal amounts of RF2 protein that lacks normal mitochondrial (mt) ALDH activity provides strong evidence that rf2-encoded mtALDH activity is required to restore male fertility to T cytoplasm maize. Detailed genetic analyses have established that the rf2 gene also is required for anther development in normal cytoplasm maize. Hence, it appears that the rf2 gene was recruited recently to function as a nuclear restorer. ALDHs typically have very broad substrate specificities. Indeed, the RF2 protein is capable of oxidizing at least three aldehydes. Hence, the specific metabolic pathway(s) within which the rf2-encoded mtALDH acts remains to be discovered. 相似文献
96.
The maize (Zea mays) rf2a and rf2b genes both encode homotetrameric aldehyde dehydrogenases (ALDHs). The RF2A protein was shown previously to accumulate in the mitochondria. In vitro import experiments and ALDH assays on mitochondrial extracts from rf2a mutant plants established that the RF2B protein also accumulates in the mitochondria. RNA gel-blot analyses and immunohistolocation experiments revealed that these two proteins have only partially redundant expression patterns in organs and cell types. For example, RF2A, but not RF2B, accumulates to high levels in the tapetal cells of anthers. Kinetic analyses established that RF2A and RF2B have quite different substrate specificities; although RF2A can oxidize a broad range of aldehydes, including aliphatic aldehydes and aromatic aldehydes, RF2B can oxidize only short-chain aliphatic aldehydes. These two enzymes also have different pH optima and responses to changes in substrate concentration. In addition, RF2A, but not RF2B or any other natural ALDHs, exhibits positive cooperativity. These functional specializations may explain why many species have two mitochondrial ALDHs. This study provides data that serve as a basis for identifying the physiological pathway by which the rf2a gene participates in normal anther development and the restoration of Texas cytoplasm-based male sterility. For example, the observations that Texas cytoplasm anthers do not accumulate elevated levels of reactive oxygen species or lipid peroxidation and the kinetic features of RF2A make it unlikely that rf2a restores fertility by preventing premature programmed cell death. 相似文献
97.
The widespread use of the maize Mutator (Mu) system to generate mutants exploits the preference of Mu transposons to insert into genic regions. However, little is known about the specificity of Mu insertions within genes. Analysis of 79 independently isolated Mu-induced alleles at the gl8 locus established that at least 75 contain Mu insertions. Analysis of the terminal inverted repeats (TIRs) of the inserted transposons defined three new Mu transposons: Mu10, Mu 11, and Mu12. A large percentage (>80%) of the insertions are located in the 5' untranslated region (UTR) of the gl8 gene. Ten positions within the 5' UTR experienced multiple independent Mu insertions. Analyses of the nucleotide composition of the 9-bp TSD and the sequences directly flanking the TSD reveals that the nucleotide composition of Mu insertion sites differs dramatically from that of random DNA. In particular, the frequencies at which C's and G's are observed at positions -2 and +2 (relative to the TSD) are substantially higher than expected. Insertion sites of 315 RescueMu insertions displayed the same nonrandom nucleotide composition observed for the gl8-Mu alleles. Hence, this study provides strong evidence for the involvement of sequences flanking the TSD in Mu insertion-site selection. 相似文献
98.
Background
Specification of primordial germ cells in mice depends on instructive signalling events, which act first to confer germ cell competence on epiblast cells, and second, to impose a germ cell fate upon competent precursors. fragilis, an interferon-inducible gene coding for a transmembrane protein, is the first gene to be implicated in the acquisition of germ cell competence. 相似文献99.