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11.
Rice has evolved metabolic and morphological adaptations to low-oxygen stress to grow in submerged paddy fields. To characterize the molecular components that mediate the response to hypoxia in rice, we identified low-oxygen stress early response genes by microarray analysis. Among the highly responsive genes, five genes, OsHREF1 to OsHREF5, shared strong homology. They encoded small proteins harboring two EF-hands, typical Ca2+-binding motifs. Homologous genes were found in many land plants, including SlHREF in tomato, which is also strongly induced by hypoxia. SlHREF induction was detected in both roots and shoots of tomato plants under hypoxia. With the exception of OsHREF5, OsHREF expression was unaffected by drought, salinity, cold, or osmotic stress. Fluorescent signals of green fluorescent protein-fused OsHREFs were detected in the cytosol and nucleus. Ruthenium red, an inhibitor of intracellular Ca2+ release, repressed induction of OsHREF1-4 under hypoxia. The HREFs may be related to the Ca2+ response to hypoxia.  相似文献   
12.
Endogenous cytokinins in alfalfa were isolated, and identified by mass spectrometry, trans- Ribosylzeatin (RZ) and ribosyldihydrozeatin (DHRZ) were identified from the root, and the combined content (benzyladenine equivalent) was estimated to be approximately 0.5/μg/100 g of fresh weight, eis- and trans-KL were identified from the stems and leaves. The relative content of the m-isomer was approximately five times greater than that of the trans-isomer.  相似文献   
13.
The kinetics of decomposition of the 3-substituted-phenyl-1-nitroso-1-methylureas was studied under a certain pH and various temperatures. It was observed that the rate of decomposition is first order in concentration of the nitroso compound under the constant pH and that the more the electron withdrawal of the ring substituent, the larger is the rate of decomposition. From the temperature dependence of the rate, the apparent enthalpy and entropy of activation were determined. The sequence of the rate of decomposition of this series of compounds was found to be governed largely by the variation of the entropy rather than that of the enthalpy of activation.  相似文献   
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The Dictyostelium class I myosins, MyoA, -B, -C, and -D, participate in plasma membrane-based cellular processes such as pseudopod extension and macropinocytosis. Given the existence of a high affinity membrane-binding site in the C-terminal tail domain of these motor proteins and their localized site of action at the cortical membrane-cytoskeleton, it was of interest to determine whether each myosin I was directly associated with the plasma membrane. The membrane association of a myosin I heavy chain kinase that regulates the activity of one of the class I myosins, MyoD was also examined. Cellular fractionation experiments revealed that the majority of the Dicyostelium MyoA, -B, -C and -D heavy chains and the kinase are cytosolic. However, a small, but significant, fraction (appr. 7. -15%) of each myosin I and the kinase was associated with the plasma membrane. The level of plasma membrane-associated MyoB, but neither that of MyoC nor MyoD, increases up to 2-fold in highly motile, streaming cells. These results indicate that Dictyostelium specifically recruits myoB to the plasma membrane during directed cell migration, consistent with its known role in pseudopod formation.  相似文献   
16.
The endogenous metabolites of the coelomic fluid of the earthworm Eisenia veneta were characterised using high-resolution one-dimensional and two-dimensional 1H nuclear magnetic resonance spectroscopy. Signals from common organic acids, such as acetate, fumarate, malonate, malate, formate, and succinate, were identified together with adenosine and nicotinamide mononucleotide. The potential use of this information as a baseline dataset for future toxicological or physiological studies was demonstrated by a metabonomic analysis: a series of earthworms were dosed with the model compound 3-fluoro-4-nitrophenol, and toxic effects followed by multivariate analysis of the spectral data of the coelomic fluid. Relative concentrations of acetate and malonate were decreased in the dosed worms compared to the controls.  相似文献   
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BphC derived from Pseudomonas sp. strain KKS102, an extradiol type catecholic dioxygenase, is a non-heam iron-containing enzyme, playing an important role in the degradation of biphenyl/PCB (Poly Chlorinated Biphenyls) in the microbe. Although we had earlier solved the crystal structure of KKS102 BphC, it was the inactive form with Fe(III) in the active site. In order to determine the active form structure, BphC was re-activated by anaerobic incubation with Fe(II) and ascorbate, and crystallized anaerobically. The crystal structures of activated BphC and its substrate complex (E x S complex) were determined at 2.0 A resolution under cryogenic condition. In addition, crystal structures of unactivated BphC in substrate free and complex forms were also re-determined. Comparison of activated and unactivated E x S complexes reveals that the orientation of the bound substrate in the active site is significantly different between the two. The structural comparison of the substrate free and complex forms of activated BphC show certain small conformational shifts around the active site upon substrate binding. As a result of the conformational shifts, His194, which has been suggested as the catalytic base, takes part in a weak hydrogen bond with hydroxyl group of the substrate.  相似文献   
19.
We previously characterized LePRK1 and LePRK2, pollen-specific receptor kinases from tomato (Muschietti et al., 1998). Here we identify a similar receptor kinase from maize, ZmPRK1, that is also specifically expressed late in pollen development, and a third pollen receptor kinase from tomato, LePRK3. LePRK3 is less similar to LePRK1 and LePRK2 than either is to each other. We used immunolocalization to show that all three LePRKs localize to the pollen tube wall, in partially overlapping but distinct patterns. We used RT-PCR and degenerate primers to clone homologues of the tomato kinases from other Solanaceae. We deduced features diagnostic of pollen receptor kinases and used these criteria to identify family members in the Arabidopsis database. RT-PCR confirmed pollen expression for five of these Arabidopsis candidates; two of these are clearly homologues of LePRK3. Our results reveal the existence of a distinct pollen-specific receptor kinase gene family whose members are likely to be involved in perceiving extracellular cues during pollen tube growth.  相似文献   
20.
Detachment of anchorage-dependent normal epithelial cells from their substratum causes the type of apoptosis known as anoikis, whereas malignant cells can proliferate independently of anchorage. Because src and ras oncogenes are activated in many human cancers, we investigated their role and downstream signaling pathways in anoikis resistance, using HAG-1 human epithelial cells transfected with v-src or activated H-ras. Consequently, anchorage-dependent mock- or ras-transfected cells underwent anoikis. In contrast, anchorage-independent v-Src-transformed cells did not exhibit such apoptotic features. Focal adhesion kinase (FAK), a transducer of integrin, was only activated in v-Src-transformed cells. Herbimycin A, an Src kinase inhibitor, reduced tyrosyl phosphorylation of FAK and reversed resistance to anoikis. However, both protein kinase C (PKC) and phophatidylinositol-3 (PI-3) kinase inhibitors failed to induce anoikis. These data suggest that the ability of activated Src to prevent anoikis may be mediated by Src to a downstream signaling pathway involving FAK, but not Ras, PI-3 kinase, or PKC.  相似文献   
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