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Two soybean cDNA clones, SPK-3 and SPK-4, encoding putative protein kinases were isolated and characterized. Both cDNAs encoded approximately 40-kDa serine/threonine kinases with unusual stretches of acidic amino acids in their carboxy-terminal regions, which are highly homologous to PKABA1 from wheat and ASKs from Arabidopsis. These kinases are encoded by one- or two-copy genes in the soybean genome. Notably, SPK-3 and -4 showed different patterns of expression in various soybean tissues. SPK-3 is highly expressed in dividing and elongating tissues of young seedlings but relatively weakly in tissues of mature plants. In contrast, SPK-4 showed relatively high and constitutive expression in all the tissues examined except for leaf tissues of mature plants. Although various stressors, such as dehydration and high salinity, increased the expression of both genes, the induction kinetics were different. The two genes also differed in their response to abscisic acid (ABA). SPK-3 was induced but SPK-4 was not affected by exogenously supplied abscisic acid. In accordance with these expression data analysis of the activity of a chimeric SPK-3 promoter::beta-glucuronidase (GUS) reporter gene by transient expression in tobacco leaves confirmed the inducibility of SPK-3 by salt and ABA. Polyclonal antibodies raised against a recombinant SPK-4 protein produced in Escherichia coli specifically recognized both recombinant SPK-3 and -4 proteins. Kinase assays using affinity-purified SPK-4/ antibody complexes with crude soybean extracts as substrate identified specific phosphorylation of two 41 and 170 kDa soybean proteins that were phosphorylated on serine residues. Taken together, our results suggest that SPK-3, and/or SPK-4 are functional serine protein kinase(s). Furthermore, SPK-3 and -4 may play different roles in the transduction of various environmental stresses.
Mol Gen Genet 1997 Jul
PMID:Differential expression of two functional serine/threonine protein kinases from soybean that have an unusual acidic domain at the carboxy terminus. 926 31

In the initial experiments reviewed here, we show that atrial natriuretic peptide (ANP) plays an important inhibitory role in the control of sodium chloride and water intake since injections of ANP into the third ventricle (3V) caused a reduction in dehydration-induced drinking and also the drinking of salt in salt-depleted rats. Attention was then turned to the possible role of the brain ANP neurons in producing natriuresis which had earlier been shown to be caused by stimulations within the anterior ventral third ventricular region (AV3V). Stimulation in this region by carbachol produced natriuresis accompanied by a dramatic increase in plasma ANP concentrations and increased content of the peptide in medial basal hypothalamus (MBH), neurohypophysis (NH) and anterior pituitary gland (AP), without alterations in the content of ANP in lungs or atria. This suggested that the natriuresis resulting from the stimulation is brought about, at least in part, by the release of ANP from the brain. Conversely, there was a dramatic decline in plasma ANP at both 24 and 128 h after AV3V lesions had been placed. In view of the much larger quantities of the peptide stored in the atria, it is probable that the changes in the atrial release of the peptide were the main factors altering plasma ANP, but that there was concomitant alteration in the release of brain ANP as well. Blood volume expansion (BVE) by intraatrial injection of isotonic saline in the rat is a profound stimulus for ANP release. Lesions in the AV3V region, median eminence, or neurohypophysectomy blocked BVE-induced release of ANP indicating the crucial participation of the CNS in the response of ANP and natriuresis. Baroreceptor impulses from the carotid-aortic sinus regions and the kidney are important in the neuroendocrine control of ANP release since deafferentation of these regions lowered basal plasma ANP concentrations and prevented the increase after BVE. The evidence indicates that the ANP release, in response to BVE, is mediated by afferent baroreceptor impulses to the AV3V, which mediates the increased ANP release via activation of the hypothalamic ANP neuronal system. Our recent data support the hypothesis that BVE causes the release of ANP from ANPergic neurons in the hypothalamus that in turn stimulates release of oxytocin from the neurohypophysis. This oxytocin acts to release ANP from the right atrium that has negative chrono- and inotropic effects in the right atrium to reduce cardiac output, thereby reducing effective circulating blood volume. Then, the released ANP circulates to the kidneys and evokes natriuresis to return circulating blood volume to normal. This is further accomplished by reduction in intake of water and salt mediated also by brain ANP.
Mol Psychiatry 1997 Sep
PMID:The neuroendocrine control of atrial natriuretic peptide release. 932 24

Six cDNA clones from Phaseolus vulgaris, whose expression is induced by water deficit and ABA treatment (rsP cDNAs) were identified and characterized. The sequence analyses of the isolated clones suggest that they encode two types of late-embryogenesis abundant (LEA) proteins, a class-1 cytoplasmic low-molecular-weight heat shock protein (lmw-HSP), a lipid transfer protein (LTP), and two different proline-rich proteins (PRP). One of the putative LEA proteins identified corresponds to a novel 9.3 kDa LEA-like protein. During the plant response to a mild water deficit (psi w = -0.35 MPa) all genes identified present a maximal expression at around 16 or 24 h of treatment, followed by a decline in expression levels. Rehydration experiments revealed that those genes encoding PRPs and LTP transiently re-induce or maintain their expression when water is added to the soil after a dehydration period. This is not the case for the lea genes whose transcripts rapidly decrease, reaching basal levels a few hours after rehydration (4 h). Under water deficit and ABA treatments, the highest levels of expression for most of the genes occur in the root, excluding the ltp gene whose maximum expression levels are found in the aerial regions of the plant. This indicates that for these genes, both water deficit and ABA-dependent expression are under organ-specific control. The data presented here support the importance of these proteins during the plant response to water deficit.
Plant Mol Biol 1997 Nov
PMID:Characterization of Phaseolus vulgaris cDNA clones responsive to water deficit: identification of a novel late embryogenesis abundant-like protein. 934 63

A simple homopolymeric purine:purine.pyrimidine, d(GA)n:d(GA)n.d(TC)n, triplex DNA was generated in the presence of magnesium ion at neutral pH. Hydrogen bonding of the N7 positions of guanines and adenines was investigated by 7-deaza base substitutions and protection from chemical modification by dimethyl sulfate (DMS). Chemical modification of this triplex with DMS revealed an unexpected triplex specific hypermodification in the N3 positions of the adenines in addition to the protection in the N7 positions of the guanines. The significance of this increase in the chemical accessibility of the N3 positions of adenines in the minor groove and possible relevance of dehydration to the mechanism of triplex formation and stability is discussed.
Mol Cells 1997 Oct 31
PMID:An alteration in the structure of the minor groove of duplex DNA induced by the formation of an intermolecular d(GA)n:d(GA)n.d(TC)n triplex. 938 52

Molecular dynamics simulations reveal that, in C3'-endo sugar puckers, only three orientations are accessible to the 2'-hydroxyl groups distinctive of RNA molecules: towards (i) the O3', (ii) the O4' of the same sugar, and (iii) the shallow groove base atoms. In the rarer C2'-endo sugar puckers, orientations towards the O3' atom of the same sugar are strongly favoured. Surprisingly, in helical regions, the frequently suggested intra-strand O2'-H(n)...O4'(n+1) interaction is not found. This observation led to the detection of an axial C-H...O interaction between the C2'-H2'(n) group and the O4'(n+1) atom contributing to the stabilization of RNA helical regions. Subsequent analysis of crystallographic structures of both RNA and A-DNA helices fully supports this finding. Specific hydration patterns are also thought to play a significant role in the stabilization of RNA structures. In the shallow groove of RNA, known as a favourable RNA or protein-binding region, three well-defined hydration sites are located around the O2' atom. These hydration sites, occupied by water molecules exchanging with the bulk, constitute, after dehydration, anchor points for specific interactions between RNA and nucleic acids, proteins or drugs. Therefore, the fact that the 2'-hydroxyl group is not monopolised by axial stabilization, together with its water-like behaviour, facilitates complex formation involving RNA helical regions.
J Mol Biol 1997 Nov 21
PMID:Rules governing the orientation of the 2'-hydroxyl group in RNA. 939 15

Plant storage proteins comprise a major part of the human diet. Sequence analysis has revealed that these proteins probably share a common ancestor with a fungal oxalate decarboxylase and/or related bacterial genes. Additionally, all these proteins share a central core sequence with several other functionally diverse enzymes and binding proteins, many of which are associated with synthesis of the extracellular matrix during sporulation/encystment. A possible prokaryotic relative of this sequence is a bacterial protein (SASP) known to bind to DNA and thereby protect spores from extreme environmental conditions. This ability to maintain cell viability during periods of dehydration in spores and seeds may relate to absolute conservation of residues involved in structure determination.
J Mol Evol 1998 Feb
PMID:Microbial relatives of seed storage proteins: conservation of motifs in a functionally diverse superfamily of enzymes 945 16

A cDNA encoding the multifunctional cytochrome P450, CYP71E1, involved in the biosynthesis of the cyanogenic glucoside dhurrin from Sorghum bicolor (L.) Moench was isolated. A PCR approach based on three consensus sequences of A-type cytochromes P450- (V/I)KEX(L/F)R, FXPERF, and PFGXGRRXCXG-was applied. Three novel cytochromes P450 (CYP71E1, CYP98, and CYP99) in addition to a PCR fragment encoding sorghum cinnamic acid 4-hydroxylase were obtained. Reconstitution experiments with recombinant CYP71E1 heterologously expressed in Escherichia coli and sorghum NADPH-cytochrome P450-reductase in L-alpha-dilaurylphosphatidyl choline micelles identified CYP71E1 as the cytochrome P450 that catalyses the conversion of p-hydroxyphenylacetaldoxime to p-hydroxymandelonitrile in dhurrin biosynthesis. In accordance to the proposed pathway for dhurrin biosynthesis CYP71E1 catalyses the dehydration of the oxime to the corresponding nitrile, followed by a C-hydroxylation of the nitrile to produce p-hydroxymandelonitrile. In vivo administration of oxime to E. coli cells results in the accumulation of the nitrile, which indicates that the flavodoxin/flavodoxin reductase system in E. coli is only able to support CYP71E1 in the dehydration reaction, and not in the subsequent C-hydroxylation reaction. CYP79 catalyses the conversion of tyrosine to p-hydroxyphenylacetaldoxime, the first committed step in the biosynthesis of the cyanogenic glucoside dhurrin. Reconstitution of both CYP79 and CYP71E1 in combination with sorghum NADPH-cytochrome P450-reductase resulted in the conversion of tyrosine to p-hydroxymandelonitrile, i.e. the membranous part of the biosynthetic pathway of the cyanogenic glucoside dhurrin. Isolation of the cDNA for CYP71E1 together with the previously isolated cDNA for CYP79 provide important tools necessary for tissue-specific regulation of cyanogenic glucoside levels in plants to optimize food safety and pest resistance.
Plant Mol Biol 1998 Feb
PMID:Cloning of three A-type cytochromes P450, CYP71E1, CYP98, and CYP99 from Sorghum bicolor (L.) Moench by a PCR approach and identification by expression in Escherichia coli of CYP71E1 as a multifunctional cytochrome P450 in the biosynthesis of the cyanogenic glucoside dhurrin. 948 80

The relationship of imposed water activity a(w) (equilibrium relative humidity) with conventional water status parameters and proton spin-lattice relaxation time T1 of leaf water was studied in pearl millet and wheat. The water activities of different levels were created by equilibrating the leaves in varying concentrations of PEG-6000 solutions. With decreasing a(w), relative water content and T1 decreased linearly and other variables (leaf water potential and leaf water content) decreased exponentially upto a dehydration level of a(w) approximately 0.978 for pearl millet, 0.986 for drought susceptible wheat var. HD2329 and 0.975 for tolerant wheat var. C306. Below that level there was abrupt reduction in all parameters except T1 which registered an increase. The changes in short and long components of T1 with changes in a(w) have also have been discussed for pearl millet.
Cell Mol Biol (Noisy-le-grand) 1997 Dec
PMID:Relationship between NMR relaxation characteristics and water activity in cereal leaves. 948 44

A major pathway for K+ efflux in human reticulocytes and young RBCs is K:Cl cotransport (K:Cl-CT). The activity of K:Cl-CT is increased in pathologic RBCs containing hemoglobins S and C and may contribute to the abnormal dehydration state of these cells. Human K:Cl-CT (gene product KCC1) has been recently sequenced from human (hKCC1), rabbit and rat tissue by Gillen et al. (J Biol Chem 271:16237, 1996). We report here the sequence of KCC1 from human and mouse erythroleukemic cells (K562 and MEL cells, respectively). The cDNA for human erythroid-KCC1 is 100% identical to hKCC1 and the cDNA for mouse erythroid-KCC1 shares 89% identity with hKCC1, which translates to 96% identity at the amino acid level. Mammalian KCC1 is strongly conserved with >95% identity between human, rabbit, rat, and mouse KCC1 proteins. We did not detect any full-length mRNA transcripts of human erythroid-KCC1 in circulating reticulocytes. We detected two mRNA isoforms of human erythroid-KCC1 that resulted in C-terminal truncated proteins (73 amino acid and 17 amino acids, respectively). Human and mouse erythroidKCC1 differed at several consensus sites including a predicted PKC phosphorylation site at 108threonine and a predicted CK2 phosphorylation site at 51serine, within the predicted cytoplasmic N-terminal, that are present in human but not mouse erythroid-KCC1. Expression of MEL-KCC1 mRNA increases substantially upon DMSO-induced differentiation opening the possibility that erythroid-KCC1 plays a role in early erythroid maturation events. The molecular identification of erythroid-KCC1 is an important step towards understanding the physiologic role mediated by this protein in young and pathologic RBCs and during erythropoiesis, as well as providing a new tool for the elucidation of pathways and signals involved in RBC volume regulation.
Blood Cells Mol Dis 1998 Mar
PMID:Molecular identification and expression of erythroid K:Cl cotransporter in human and mouse erythroleukemic cells. 951 79

1. Magnocellular neurosecretory cells (MNCs) in the rat hypothalamus adopt a phasic pattern of spike discharge under conditions demanding enhanced vasopressin release, such as during dehydration or hemorrhage. The emergence of phasic firing minimizes the occurrence of secretory fatigue from the axon terminals of MNCs, thereby maximizing vasopressin release from the neurohypophysis. 2. Intracellular and whole-cell recordings from hypothalamic slices or explants in vitro have shown that phasic firing is supported by the presence of a plateau potential which arises from the summation of spike depolarizing afterpotentials (DAPs). Modulatory actions of neurotransmitters on the amplitude of the DAP, therefore, represent possible mechanisms by which the expression of phasic firing may be regulated in vivo. 3. Here we review the basis for phasic firing in MNCs of the rat supraoptic nucleus and present recent findings concerning the direct and indirect mechanisms through which selected neurotransmitters have been found to regulate the amplitude of DAPs.
Cell Mol Neurobiol 1998 Feb
PMID:Extrinsic modulation of spike afterpotentials in rat hypothalamoneurohypophysial neurons. 952 26


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