Rhizobium nod genes are involved in the induction of two early nodulin genes in Vicia sativa root nodules

Nodulin gene expresison was studied in Vicia sativa (common vetch) root nodules induced by several Rhizobium and Agrobacterium strains. An Agrobacterium transconjugant containing a R. leguminosarum symplasmid instead of its Ti-plasmid, that was previously shown to form empty nodules on pea, induced nodules on Vicia roots in which nodule cells were infected with bacteria. In the Vicia nodules induced by this transconjugant, two so-called early nodulin genes were found to be expressed, whereas in the nodules formed on pea the expression of only one early nodulin gene was detected. In both cases the majority of the nodulin genes was not expressed.Apparently, an intracellular location of the bacteria is not sufficient for the induction of the majority of the nodulin genes. All nodulin genes were expressed in nodules induced by cured Rhizobium strains containing cosmid clones that have a 10 kb nod region of the sym-plasmid in common. Since in tumours no nodulin gene expression was found at all, the Agrobacterium chromosome does not contribute to the induction of nodulin genes. Therefore it is concluded that the signal for the induction of the expression of the two Vicia early nodulin genes is encoded by the nod-region, and the signal involved in the induction of all other nodulin genes has to be located outside the sym-plasmid, on the Rhizobium chromosome. The apparent difference in early nodulin gene expression between pea and Vicia is discussed in the light of the usefulness of Agrobacterium transconjugants in the study of nodulin gene expression.     

Germin-like genes are expressed during somatic embryogenesis and early development of conifers

Germins and germin-like proteins (GLPs) are members of a superfamily of proteins widely distributed in plants. Their localization within the extracellular matrix and in some cases their hydrogen peroxide-producing activity suggests that these proteins are involved in cell wall metabolism during stress responses and developmental processes. Several very highly conserved conifer GLPs have been identified in somatic embryo tissues. In order to gain more knowledge on their potential involvement in the development of this particular tissue, we have characterized a new GLP gene, LmGER1 in hybrid larch. Anti-GLP immunserum and in-gel activity analyses suggested the presence of superoxide dismutase activity in apoplastic proteins from larch somatic embryos. These results could indicate a possible role for LmGER1 in this physiological process. The expression of LmGER1 has been followed during the maturation of somatic embryos and in different organs of young plantlets by homologous transformation with a promoter-gus construct. This promoter was activated in the root cap of young embryos and, later on, in the cotyledons and in the vascular procambium and xylem. Furthermore, the importance of this gene in embryo development was evaluated by transforming embryonal masses with a gene construct encoding a hairpin RNA leading to gene silencing. The potential role of LmGER1 in cross-linking of cell wall components is discussed.     

Segments of bacteriophage lambda (orf 221) and phi 80 are homologous to genes coding for mammalian protein phosphatases

The amino acid sequences of mammalian protein phosphatase 1 and 2A were compared pairwise with every sequence in the National Biomedical Research Foundation protein sequence database using an exhaustive searching programme [Coulson et al., Comp. J. 30 (1987) 420-424]. The N-terminal half of the protein encoded by an open reading frame, orf 221, in bacteriophage lambda (nt 43,224-43,886 in the map of Daniels et al. [in Hendrix et al. (Eds.), Lambda II. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 1983, pp. 519-676] shows 35% identity to either protein phosphatase 1 or 2A in this region. If conservative replacements are included the overall homology rises to 49%. A gene in phi 80 also shows 35% identity with the mammalian protein phosphatases. The results indicate that orf 221 of phage lambda and the homologous phi 80 gene may encode protein phosphatases. The possible roles of protein phosphorylation in the propagation of bacteriophage are discussed.     

All four zebrafish Wnt7 genes are expressed during early brain development

Wnt-signalling is involved in a number of biological processes in the course of embryonic development, cell fate determination, proliferation, stem cell maintenance and oncogenesis. Wnt ligands are secreted glycoproteins and the number of Wnt isoforms varies between five in nematodes and 27 in fish. The highly conserved group of Wnt7 genes has been found to signal via at least three Wnt-signalling pathways dependent on the developmental context. These ligands have been identified as important regulators in a number of processes ranging from formation of bones, lungs, kidneys, reproductive organs and placenta to vasculogenesis and synaptogenesis in the brain. The importance of Wnt7 function is underscored by their implication in disease syndromes in man. Unlike the single Wnt7a and Wnt7b mammalian genes we find that the zebrafish genome contains two paralogues genes for each Wnt7 ligand. Here, we compare these four Wnt7 genes evolutionarily and analyse their expression during the first two days of embryonic development. We find Wnt7 genes mainly expressed in a number of CNS structures at developmental stages at which patterning and neural specification takes place. The timely and spatially overlapping as well as complementary gene expression suggests diverse as well as redundant involvements during brain development.     

Absence of endogenous interleukin-6 enhances the inflammatory response during acute pancreatitis induced by cerulein in mice

Interleukin-6 (IL-6) exerts a wide spectrum of regulatory activities during immune and inflammatory responses. The aim of this study was to investigate the role of endogenous IL-6 in the inflammatory response associated with acute pancreatitis. Acute pancreatitis was induced by hourly (x5) i.p. injections of cerulein (50 microg/kg, suspended in saline solution) in IL-6 deficient mice (IL-6-KO) and wild-type (IL-6WT) littermates. IL-6KO mice exhibited a more severe tissue injury and a higher rate of mortality and when compared to IL-6WT mice. Acute pancreatitis was characterized by edema, neutrophil infiltration, tissue hemorrhage and cell necrosis, upregulation of P-selectin and intercellular adhesion molecule-1 (ICAM-1), as well as increases in the serum levels of amylase and lipase. The degree of oxidative and nitrosative tissue damage was significantly greater in IL-6KO mice than in wild-type littermates, as indicated by higher tissue levels of malondialdehyde and nitrosylated proteins. Plasma levels of the inflammatory cytokines tumour necrosis factor-alpha and interleukin-1beta were also greatly enhanced in IL-6KO mice when compared to wild-type mice. These events were correlated with an increase in the staining (immunoreactivity) for poly (ADP-ribose) polymerase (PARP) in the pancreas of cerulein-treated IL-6WT. The staining for PARP was more pronounced in IL-6KO mice subjected to acute pancreatitis than in the corresponding WT mice. These data demonstrate that endogenous IL-6 exerts an anti-inflammatory role during acute pancreatitis, possibly by regulating the expression of adhesion molecules, the subsequent adhesion and activation of neutrophils and finally the generation of cytokine and reactive oxygen or nitrogen species.     

Auxin-regulated genes encoding cell wall-modifying proteins are expressed during early tomato fruit growth

An expansin gene, LeExp2, was isolated from auxin-treated, etiolated tomato (Lycopersicon esculentum cv T5) hypocotyls. LeExp2 mRNA expression was restricted to the growing regions of the tomato hypocotyl and was up-regulated during incubation of hypocotyl segments with auxin. The pattern of expression of LeExp2 was also studied during tomato fruit growth, a developmental process involving rapid cell enlargement. The expression of genes encoding a xyloglucan endotransglycosylase (LeEXT1) and an endo-1, 4-beta-glucanase (Cel7), which, like LeExp2, are auxin-regulated in etiolated hypocotyls (C. Catalá, J.K.C. Rose, A.B. Bennett [1997] Plant J 12: 417-426), was also studied to examine the potential for synergistic action with expansins. LeExp2 and LeEXT1 genes were coordinately regulated, with their mRNA accumulation peaking during the stages of highest growth, while Cel7 mRNA abundance increased and remained constant during later stages of fruit growth. The expression of LeExp2, LeEXT1, and Cel7 was undetectable or negligible at the onset of and during fruit ripening, which is consistent with a specific role of these genes in regulating cell wall loosening during fruit growth, not in ripening-associated cell wall disassembly.     

Redox regulation of protein tyrosine phosphatases during receptor tyrosine kinase signal transduction

In addition to protein phosphorylation, redox-dependent post-translational modification of proteins is emerging as a key signaling system that has been conserved throughout evolution and that influences many aspects of cellular homeostasis. Both systems exemplify dynamic regulation of protein function by reversible modification, which, in turn, regulates many cellular processes such as cell proliferation, differentiation and apoptosis. In this article we focus on the interplay between phosphorylation- and redox-dependent signaling at the level of phosphotyrosine phosphatase-mediated regulation of receptor tyrosine kinases (RTKs). We propose that signal transduction by oxygen species through reversible phosphotyrosine phosphatase inhibition, represents a widespread and conserved component of the biochemical machinery that is triggered by RTKs.     

Cadmium activates the mitogen-activated protein kinase (MAPK) pathway via induction of reactive oxygen species and inhibition of protein phosphatases 2A and 5

Cadmium (Cd), a highly toxic environmental pollutant, induces neurodegenerative diseases. Recently we have demonstrated that Cd may induce neuronal apoptosis in part through activation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (Erk1/2) pathways. However, the underlying mechanism remains enigmatic. Here we show that Cd induced generation of reactive oxygen species (ROS), leading to apoptosis of PC12 and SH-SY5Y cells. Pretreatment with N-acetyl-L-cysteine (NAC) scavenged Cd-induced ROS, and prevented cell death, suggesting that Cd-induced apoptosis is attributed to its induction of ROS. Furthermore, we found that Cd-induced ROS inhibited serine/threonine protein phosphatases 2A (PP2A) and 5 (PP5), leading to activation of Erk1/2 and JNK, which was abrogated by NAC. Overexpression of PP2A or PP5 partially prevented Cd-induced activation of Erk1/2 and JNK, as well as cell death. Cd-induced ROS was also linked to the activation of caspase-3. Pretreatment with inhibitors of JNK (SP600125) and Erk1/2 (U0126) partially blocked Cd-induced cleavage of caspase-3 and prevented cell death. However, zVAD-fmk, a pan caspase inhibitor, only partially prevented Cd-induced apoptosis. The results indicate that Cd induction of ROS inhibits PP2A and PP5, leading to activation of JNK and Erk1/2 pathways, and consequently resulting in caspase-dependent and -independent apoptosis of neuronal cells. The findings strongly suggest that the inhibitors of JNK, Erk1/2, or antioxidants may be exploited for prevention of Cd-induced neurodegenerative diseases.     

Tight linkage of pyruvate kinase (PKLR) and glucocerebrosidase (GBA) genes

Two polymorphisms, one in the liver-type pyruvate kinase gene (PKLR) and one in the glucocerebrosidase gene (GBA), both of which are on band q21 of chromosome 1, were found to be tightly linked. Each of three Gaucher disease mutations in 112 chromosomes studied was associated with a unique haplotype. With a conservative assumption about the length of time that the Gaucher disease mutation has been present in the Jewish population, we deduce that the genetic distance between these two loci is probably under 0.2 centimorgans. Four haplotypes are produced by these polymorphic loci, but two of these are relatively uncommon because the polymorphic sites are in linkage disequilibrium. Nonetheless these markers are potentially useful in the prenatal diagnosis of pyruvate kinase deficiency in families who have at least one affected child and may also be helpful in heterozygote detection in families with Gaucher disease where a specific mutation producing the disease in unknown.