Salt stress activation of wound-related genes in tomato plants

Plants respond to various stresses by expressing distinct sets of genes. The effects of multiple stresses on plants and their interactions are not well understood. We have discovered that salt stress causes the accumulation of proteinase inhibitors and the activation of other wound-related genes in tomato (Lycopersicon esculentum) plants. Salt stress was also found to enhance the plant's response to wounding locally and systemically. The tomato mutant (def-1), which has an impairment in the octadecanoid pathway, displayed a severe reduction in the accumulation of proteinase inhibitors under salt stress, indicating that salt stress-induced accumulation of proteinase inhibitors was jasmonic acid dependent. The analysis of salt stress in another tomato mutant, spr-1, which carries a mutation in a systemin-specific signaling component, and transgenic tomato plants that express an antisense-prosystemin cDNA, showed that prosystemin activity was not required for the salt-induced accumulation of proteinase inhibitors, but was necessary to achieve maximal levels. These results suggest that a prosystemin independent- but jasmonic acid-dependent pathway is utilized for proteinase inhibitor accumulation in response to salt stress.     

Estimation of carcass fat and protein in northern pintails (Anas acuta) during spring migration

Foraging in stopover areas influences nutritional condition of birds during spring migration. Our purpose was to determine if body mass, percent carcass water, and serum biochemistry would predict energy reserves (carcass fat and protein) in northern pintails (Anas acuta) at a spring staging area, Lake St. Pierre in Québec, Canada (46 degrees 11 'N, 73 degrees 08 'W). Northern pintails were collected during spring 1997 (14 April-9 May). In this staging area, body mass and percent body water successfully estimated carcass protein and fat in male northern pintails, but only carcass protein in females. None of the seven blood parameters we used accurately estimated nutritional reserves in staging northern pintails. These findings suggest that investigators must use direct estimates of carcass reserves to examine nutrient reserve requirements for egg production, migration, or body maintenance during spring migration.     

Involvement of integrins in osmosensing and signaling toward autophagic proteolysis in rat liver

Inhibition of autophagic proteolysis by hypoosmotic or amino acid-induced hepatocyte swelling requires osmosignaling toward p38MAPK; however, the upstream osmosensing and signaling events are unknown. These were studied in the intact perfused rat liver with a preserved in situ environment of hepatocytes. It was found that hypoosmotic hepatocyte swelling led to an activation of Src (but not FAK), Erks, and p38MAPK, which was prevented by the integrin inhibitory hexapeptide GRGDSP, but not its inactive analogue GRGESP. Src inhibition by PP-2 prevented hypoosmotic MAP kinase activation, indicating that the integrin/Src system is located upstream in the osmosignaling toward p38MAPK and Erks. Inhibition of the integrin/Src system by the RGD motif-containing peptide or PP-2 also prevented the inhibition of proteolysis and the decrease in autophagic vacuole volume, which is otherwise observed in response to hypoosmotic or glutamine/glycine-induced hepatocyte swelling. These inhibitors, however, did not affect swelling-independent proteolysis inhibition by phenylalanine. In line with a role of p38MAPK in triggering the volume regulatory decrease (RVD), PP-2 and the RGD peptide blunted RVD in response to hypoosmotic cell swelling. The data identify integrins and Src as upstream events in the osmosignaling toward MAP kinases, proteolysis, and RVD. They further point to a role of integrins as osmo- and mechanosensors in the intact liver, which may provide a link between cell volume and cell function.     

Factors on the third chromosome affect the level of cyp6a2 and cyp6a8 expression in Drosophila melanogaster

The expression of two second chromosome-linked cytochrome P450 genes, Cyp6a2 and Cyp6a8, of Drosophila melanogaster was measured in various strains. Six different strains, including ry(506) and 91-C, showed low or undetectable levels of CYP6A2 and CYP6A8 mRNAs, suggesting that low expression is the wild-type phenotype of Cyp6a2 and Cyp6a8 genes. In the 91-R and MHIII-D23 strains, however, both these genes are overexpressed. In order to examine the genetic basis of Cyp6a2 and Cyp6a8 expression, CYP6A2 and CYP6A8 RNA levels were measured in the F1 hybrids of overproducer (91-R and MHIII-D23) and underproducer (ry(506) and 91-C) strains. Results showed that the total amounts of CYP6A2 and CYP6A8 mRNAs in the F1 hybrids were lower than half the amounts of these RNAs found in the overproducer parental strains. This suggested that the underproducer strains carry loci which downregulate Cyp6a2 and Cyp6a8 gene expression. To determine the chromosome linkage of these loci, several stocks homozygous for the second chromosome of overproducer 91-R strain and, therefore, homozygous for the Cyp6a2-91R and Cyp6a8-91R alleles were synthesized. The third chromosomes in all these stocks were from the underproducer ry(506) strain. The levels of expression of both Cyp6a2-91R and Cyp6a8-91R genes in these three stocks were significantly lower than that observed in the 91-R strain. One of these stocks, named iso-2, showing reduced expression, was used to synthesize two new isogenic stocks by resubstituting the third chromosome of ry(506) origin with third chromosomes of the 91-R strain. Expression of both Cyp6a2-91R and Cyp6a8-91R alleles was found to be much higher in these two resubstituted isogenic stocks than in the progenitor iso-2 stock. Taken together, these results suggest that the second chromosome-linked Cyp6a2 and Cypa8 genes are regulated by loci present on the third chromosome, and the wild-type function of these loci is to repress these two Cyp genes. The data also suggest that Cyp6a2 and Cyp6a8 overexpression in the 91-R and MHIII-D23 strains is more likely due to mutation in the repressor locus (or loci) rather than in the cis-regulatory sequences of the Cyp6a2 and Cyp6a8 genes.     

Malaria in Pregnancy Interacts with and Alters the Angiogenic Profiles of the Placenta

Malaria in pregnancy remains a substantial public health problem in malaria-endemic areas with detrimental outcomes for both the mother and the foetus. The placental changes that lead to some of these detrimental outcomes have been studied, but the mechanisms that lead to these changes are still not fully elucidated. There is some indication that imbalances in cytokine cascades, complement activation and angiogenic dysregulation might be involved in the placental changes observed. Nevertheless, the majority of studies on malaria in pregnancy (MiP) have come from areas where malaria transmission is high and usually restricted to Plasmodium falciparum, the most pathogenic of the malaria parasite species. We conducted a cross-sectional study in Cruzeiro do Sul, Acre state, Brazil, an area of low transmission and where both P. vivax and P. falciparum circulate. We collected peripheral and placental blood and placental biopsies, at delivery from 137 primigravid women and measured levels of the angiogenic factors angiopoietin (Ang)-1, Ang-2, their receptor Tie-2, and several cytokines and chemokines. We measured 4 placental parameters (placental weight, syncytial knots, placental barrier thickness and mononuclear cells) and associated these with the levels of angiogenic factors and cytokines. In this study, MiP was not associated with severe outcomes. An increased ratio of peripheral Tie-2:Ang-1 was associated with the occurrence of MiP. Both Ang-1 and Ang-2 had similar magnitudes but inverse associations with placental barrier thickness. Malaria in pregnancy is an effect modifier of the association between Ang-1 and placental barrier thickness.     

The mutation spectrum of the facilitative glucose transporter gene SLC2A2 (GLUT2) in patients with Fanconi-Bickel syndrome

We report a total of 23 novel mutations of the SLC2A2 ( GLUT2) gene in 49 patients with a clinical diagnosis of Fanconi-Bickel syndrome (FBS). Molecular genetic analysis has now been performed in more than 50% of the 109 FBS cases from 88 families that we have been able to locate world-wide since the original report in 1949. In these 49 patients, 33 different SLC2A2 mutations (9 missense, 7 nonsense, 10 frameshift, 7 splice-site) have been detected. Thus, our results confirm that mutations of SLC2A2 are the basic defect in patients with FBS. Mutations of SLC2A2 were detected in historical FBS patients in whom some of the characteristic clinical features (hepatorenal glycogen accumulation, glucose and galactose intolerance, fasting hypoglycemia, a characteristic tubular nephropathy) and the effect of therapy were described for the first time. Mutations were also found in patients with atypical clinical signs such as intestinal malabsorption, failure to thrive, the absence of hepatomegaly, or renal hyperfiltration. No single prevalent SLC2A2 mutation was responsible for a significant number of cases. In a high percentage (74%) of FBS patients, the mutation is homozygous, so we conclude that the prevalence of SLC2A2 mutations is relatively low in most populations. No mutational hot spots within SLC2A2 or even within homologous sequences among the genes for facilitative glucose transporters were detected.     

Aging impairs peritoneal but not bone marrow‐derived macrophage phagocytosis

Aging results in deterioration of the immune system, which is associated with increased susceptibility to infection and impaired wound healing in the elderly. Phagocytosis is an essential process in both wound healing and immune defence. As such, age‐related impairments in phagocytosis impact on the health of the elderly population. Phagocytic efficiency in peritoneal macrophages, bone marrow‐derived macrophages and bone marrow monocytes from young and old mice was investigated. Aging significantly impaired phagocytosis by peritoneal macrophages, both in vitro and in vivo. However, bone marrow‐derived macrophages and bone marrow monocytes did not exhibit age‐related impairments in phagocytosis, suggesting no intrinsic defect in these cells. We sought to investigate underlying mechanisms in age‐related impairments in phagocytosis by peritoneal macrophages. We hypothesized that microenvironmental factors in the peritoneum of old mice impaired macrophage phagocytosis. Indeed, macrophages from young mice injected into the peritoneum of old mice exhibited impaired phagocytosis. Proportions of peritoneal immune cells were characterized, and striking increases in numbers of T cells, B1 and B2 cells were observed in the peritoneum of old mice compared with young mice. In addition, B cell‐derived IL‐10 was increased in resting and LPS‐activated peritoneal cell cultures from old mice. These data demonstrate that aging impairs phagocytosis by tissue‐resident peritoneal macrophages, but not by bone marrow‐derived macrophages/monocytes, and suggest that age‐related defects in macrophage phagocytosis may be due to extrinsic factors in the tissue microenvironment. As such, defects may be reversible and macrophages could be targeted therapeutically in order to boost immune function in the elderly.