Rice G protein γ subunit qPE9-1 modulates root elongation for phosphorus uptake by involving 14-3-3 protein OsGF14b and plasma membrane H+-ATPase

Heterotrimeric G protein is involved in plant growth and development, while the role of rice (Oryza sativa) G protein γ subunit qPE9-1 in response to low-phosphorus (LP) conditions remains unclear. The gene expression of qPE9-1 was significantly induced in rice roots under LP conditions. Rice varieties carrying the qPE9-1 allele showed a stronger primary root response to LP than the varieties carrying the qpe9-1 allele (mutant of the qPE9-1 allele). Transgenic rice plants with the qPE9-1 allele had longer primary roots and higher P concentrations than those with the qpe9-1 allele under LP conditions. The plasma membrane (PM) H⁺-ATPase was important for the qPE9-1-mediated response to LP. Furthermore, OsGF14b, a 14-3-3 protein that acts as a key component in activating PM H⁺-ATPase for root elongation, is also involved in the qPE9-1 mediation. Moreover, the overexpression of OsGF14b in WYJ8 (carrying the qpe9-1 allele) partially increased primary root length under LP conditions. Experiments using R18 peptide (a 14-3-3 protein inhibitor) showed that qPE9-1 is important for primary root elongation and H⁺ efflux under LP conditions by involving the 14-3-3 protein. In addition, rhizosheath weight, total P content, and the rhizosheath soil Olsen-P concentration of qPE9-1 lines were higher than those of qpe9-1 lines under soil drying and LP conditions. These results suggest that the G protein γ subunit qPE9-1 in rice plants modulates root elongation for phosphorus uptake by involving the 14-3-3 protein OsGF14b and PM H⁺-ATPase, which is required for rice P use.     

Complex of N-phosphonacetyl-L-aspartate with aspartate carbamoyltransferase. X-ray refinement, analysis of conformational changes and catalytic and allosteric mechanisms

The allosteric enzyme aspartate carbamoyltransferase of Escherichia coli consists of six regulatory chains (R) and six catalytic chains (C) in D3 symmetry. The less active T conformation, complexed to the allosteric inhibitor CTP has been refined to 2.6 A (R-factor of 0.155). We now report refinement of the more active R conformation, complexed to the bisubstrate analog N-phosphonacetyl-L-aspartate (PALA) to 2.4 A (R-factor of 0.165, root-mean-square deviations from ideal bond distances and angles of 0.013 A and 2.2 degrees, respectively). The antiparallel beta-sheet in the revised segment 8-65 of the regulatory chain of the T conformation is confirmed in the R conformation, as is also the interchange of alanine 1 with the side-chain of asparagine 2 in the catalytic chain. The crystallographic asymmetric unit containing one-third of the molecule (C2R2) includes 925 sites for water molecules, and seven side-chains in alternative conformations. The gross conformational changes of the T to R transition are confirmed, including the elongation of the molecule along its threefold axis by 12 A, the relative reorientation of the catalytic trimers C3 by 10 degrees, and the rotation of the regulatory dimers R2 about the molecular twofold axis by 15 degrees. No changes occur in secondary structure. Essentially rigid-body transformations account for the movement of the four domains of each catalytic-regulatory unit; these include the allosteric effector domain, the equatorial (aspartate) domain, and the combination of the polar (carbamyl phosphate) and zinc domain, which moves as a rigid unit. However, interfaces change, for example the interface between the zinc domain of the R chain and the equatorial domain of the C chain, is nearly absent in the T state, but becomes extensive in the R state of the enzyme; also one catalytic-regulatory interface (C1-R4) of the T state disappears in the more active R state of the enzyme. Segments 50-55, 77-86 and 231-246 of the catalytic chain and segments 51-55, 67-72 and 150-153 of the regulatory chain show conformational changes that go beyond the rigid-body movement of their corresponding domains. The localized conformational changes in the catalytic chain all derive from the interactions of the enzyme with the inhibitor PALA; these changes may be important for the catalytic mechanism. The conformation changes in segments 67-72 and 150-153 of the regulatory chain may be important for the allosteric control of substrate binding. On the basis of the conformational differences of the T and R states of the enzyme, we present a plausible scheme for catalysis that assumes the ordered binding of substrates and the ordered release o     

植物激素对草莓叶片不定芽形成的影响

用试管内生长的草莓幼嫩叶片作外植体,培养在MS基本培养基上附加1.5—2.5毫克/升6—BA和0.1毫克/升NAA,可直接诱导成不定芽,诱导率可达20%。如果不定芽继代培养在同样浓度的培养基上,继而可形成大量的丛生芽。能使叶外植体形成不定芽的植物激素组合而不能使其愈伤组织分化成芽。IAA与6—BA的不同浓度组合对不定芽形成效果不明显。     

金合欢根瘤菌的几种酶活特性

金合欢根瘤菌Rhizobium sp.(Acacia farnesiana)的氧化酶、过氧化氢酶、脲酶、青霉素酶和β-半乳糖苷酶均呈阳性。经过酶活性定量测定表明金合欢根瘤菌有葡萄糖酸-6-磷酸脱氢酶(6PGD)和β-半乳糖苷酶的酶活性,而慢生型大豆根瘤菌未测到上述两种酶活性。根据聚丙烯酰胺凝胶电泳酯酶图谱,6株金合欢根瘤菌可分成两群:酋株AF1、AF2和AF3的酯酶图谱中有A带,AF4、AF5和AF6的酯酶图谱中没有A带。     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

磁场对大豆共生固氮的效应

恒定磁场处理慢生大豆根瘤菌“005”和接种后的大豆植株,发现磁场可以提高根瘤的固氮活性。在一定的磁场强度(70—100mT)下,固氮活性平均可以提高4—5倍,植株的结瘤数和根瘤重量平均提高2—3倍。从这样的根瘤中所分离出的根瘤菌,由慢生型转变成快生型,在100植株中有17株的根瘤分离出快生菌。生长世代时间和培养溶液中的pH值与慢生型不同,而与快生型相同。     

Characterization of fall armyworm mitochondrial DNA (Lepidoptera: Noctuidae)

Mitochondrial DNA from the fall armyworm, Spodoptera frugiperda (J.E. Smith), was cloned and characterized using restriction enzyme mapping. Genome size is approximately 16.3 kilobase (Kb), consistent with that of most animals. Three fragments, 8.1 Kb, 6.2 Kb, and 2.0 Kb, were produced by digestion with restriction enzyme Xbal and cloned into a pUC19 vector. Twenty-nine restriction enzymes were used to generate a detailed physical restriction enzyme map of the three cloned fragments. These data represent the first detailed characterization of a lepidopteran mitochondrial genome. © 1992 Wiley-Liss, Inc.     

The trk tyrosine protein kinase mediates the mitogenic properties of nerve growth factor and neurotrophin-3.

The product of the trk proto-oncogene encodes a receptor for nerve growth factor (NGF). Here we show that NGF is a powerful mitogen that can induce resting NIH 3T3 cells to enter S phase, grow in semisolid medium, and become morphologically transformed. These mitogenic effects are absolutely dependent on expression of gp140trk receptors, but do not require the presence of the previously described low affinity NGF receptor. gp140trk also serves as a receptor for the related factor neurotrophin-3 (NT-3), but not for brain-derived neurotrophic factor. Both NGF and NT-3 induce the rapid phosphorylation of gp140trk receptors and the transient expression of c-Fos proteins. However, NT-3 appears to elicit more limited mitogenic responses than NGF. These results indicate that the product of the trk proto-oncogene is sufficient to mediate signal transduction processes induced by NGF and NT-3, at least in proliferating cells.