Structural organization of ultrarapidly frozen barley aleurone cells actively involved in protein secretion

The ultrastructural organization of actively secreting barley (Hordeum vulgare L. cv. Himalaya) aleurone cells was examined using ultrarapid-freezing (<-10 000°C s^-1) followed by freeze-fracture and freeze-substitution. Our analysis indicates that much of the evidence supporting a direct pathway from the endoplasmic reticulum (ER) to the plasma membrane (i.e. bypassing the Golgi apparatus) for the secretion of -amylase (EC 3.2.1.1) may not be valid. Cryofixed ER cisternae show no sign of vesiculation during active -amylase secretion in gibberellic acid (GA₃)-treated cells. At the same time, Golgi complexes are abundant and numerous small vesicles are associated with the edges of the cisternae. Vesicles appear to be involved in the delivery of secretory products to the plasma membrane since depressions containing excess membrane material appear there. Treatment with GA₃ also induces changes in the composition of Golgi membranes; most notably, the density of intramembrane particles increases from 2700 m^-2 to 3800 m^-2 because of an increase of particles in the 3–8.5-nm size range. A slight decrease in 9–11-nm particles also occurs. These changes in membrane structure appear to occur as the Golgi complex becomes committed to the processing and packaging of secretory proteins. We suggest that secretory proteins in this tissue are synthesized in the abundant rough ER, packaged in the Golgi apparatus, and transported to the plasma membrane via Golgi-derived secretory vesicles. Mobilization of reserves is also accompanied by dynamic membrane events. Our micrographs show that the surface monolayer of the lipid bodies fuses with the outer leaflet of the bilayer of protein-body membranes during the mobilization of lipid reserves. Following the breakdown of the protein reserves, the protein bodies assume a variety of configurations.Abbreviations ER endoplasmic reticulum - GA₃ gibberellic acid - P protoplasmic - E exoplasmic     

Heme Amplifies the Innate Immune Response to Microbial Molecules through Spleen Tyrosine Kinase (Syk)-dependent Reactive Oxygen Species Generation

Infectious diseases that cause hemolysis are among the most threatening human diseases, because of severity and/or global distribution. In these conditions, hemeproteins and heme are released, but whether heme affects the inflammatory response to microorganism molecules remains to be characterized. Here, we show that heme increased the lethality and cytokine secretion induced by LPS in vivo and enhanced the secretion of cytokines by macrophages stimulated with various agonists of innate immune receptors. Activation of nuclear factor κB (NF-κB) and MAPKs and the generation of reactive oxygen species were essential to the increase in cytokine production induced by heme plus LPS. This synergistic effect of heme and LPS was blocked by a selective inhibitor of spleen tyrosine kinase (Syk) and was abrogated in dendritic cells deficient in Syk. Moreover, inhibition of Syk and the downstream molecules PKC and PI3K reduced the reactive oxygen species generation by heme. Our results highlight a mechanism by which heme amplifies the secretion of cytokines triggered by microbial molecule activation and indicates possible pathways for therapeutic intervention during hemolytic infectious diseases.     

Assessment of genetic diversity among sorghum landraces and their wild/weedy relatives in western Kenya using simple sequence repeat (SSR) markers

Understanding the extent of gene exchange between cultivated sorghum and its wild/weedy relatives and the evolutionary processes (including farmers’ practices) that act to shape the structure of genetic diversity within and between them is an important aspect for germplasm conservation strategies, biosafety risk assessment, and crop improvement programs. In this study, molecular characterization and genetic diversity analyses were conducted on wild, weedy and cultivated sorghums collected at a local-scale in a traditional farming system in the Lambwe Valley of western Kenya. Nine simple sequence repeat (SSR) markers were used to genotype 294 cultivated sorghum and 200 wild sorghum individuals. The nine SSR markers were highly polymorphic with a number of alleles that varied from 2 to 19. Overall, wild sorghums had higher genetic diversity, observed heterozygosity, total number of alleles, polymorphic information content and more genotypes per locus than the cultivated types. A Mantel test demonstrated that there was significant isolation-by-distance for wilds and cultivated materials. STRUCTURE, cluster and principal coordinate analyses consistently assigned wild and cultivated individuals to different groups but failed to place hybrids/weedy types as a single separate group from wilds. Our results provide strong evidence of significant genetic diversity retained within wilds, larger divergence between wild and cultivated materials and reduced gene flow than those previously reported in Kenya. These results demonstrate the value of the Lambwe Valley region as a genetic reservoir and the importance to conduct genetic diversity studies at the local scale to design and execute appropriate in situ conservation programs and policies.     

QCM-D sensitivity to protein adsorption reversibility

Using a quartz crystal microbalance with dissipative monitoring (QCM-D) we have determined the adsorption reversibility and viscoelastic properties of ribonuclease A adsorbed to hydrophobic self-assembled monolayers. Consistent with previous work with proteins unfolding on hydrophobic surfaces, high protein solution concentrations, reduced adsorption times, and low ammonium sulfate concentrations lead to increased adsorption reversibility. Measured rigidity of the protein layers normalized for adsorbed protein amounts, a quantity we term specific dissipation, correlated with adsorption reversibility of ribonuclease A. These results suggest that specific dissipation may be correlated with changes in structure of adsorbed proteins.     

Adipose tissue proadipogenic redox changes in obesity

The role of inflammation and oxidative stress in the development of obesity and associated metabolic disorders is under debate. We investigated the redox metabolism in a non-diabetic obesity model, i.e. 11-week-old obese Zucker rats. Antioxidant enzyme activities, lipophilic antioxidant (alpha-tocopherol, coenzymes Q) and hydrophilic antioxidant (glutathione, vitamin C) contents and their redox state (% oxidized form), were studied in inguinal white fat and compared with blood and liver. The adipose tissues of obese animals showed a specific higher content of hydrophilic molecules in a lower redox state than those of lean animals, which were associated with lower lipophilic molecule content and lipid peroxidation. Conversely and as expected, glutathione content decreased and its redox state increased in adipose tissues of rats subjected to lipopolysaccharide-induced systemic oxidative stress. In these in vivo models, oxidative stress and obesity thus had opposite effects on adipose tissue redox state. Moreover, the increase in glutathione content and the decrease of its redox state by antioxidant treatment promoted in vitro the accumulation of triglycerides in preadipocytes. Taken together and contrary to the emergent view, our results suggest that obesity is associated with an intracellular reduced redox state that promotes on its own the development of a deleterious proadipogenic process.     

Trinucleotide (CAG) repeat expansion in chromosomes of Spanish patients with Huntington's disease

Huntington's disease (HD) is a neurodegenerative and hereditary disease characterized by progressive movement disorders and mental and behavioral abnormalities. The HD gene is an expanding and unstable trinucleotide repeat (CAG repeat sequences). We studied 77 individuals from 38 families with HD in an attempt to obtain information for genetic counselling and differential diagnosis. Our results indicate that individuals with more than 40 repeats will be affected by the disease, whereas those with fewer than 30 will be healthy. There can be some overlap between 30 and 40 repeats, and one should be careful when interpreting these results.     

Regulation of axis determinacy by the Arabidopsis PINHEAD gene

Plants produce proximal-distal growth axes with two types of growth potential: they can be indeterminate, in which case growth continues indefinitely, or they can be determinate, in which case growth is limited to the production of a single organ or a discrete set of organs. The indeterminate shoot axes of Arabidopsis pinhead/zwille mutants frequently are transformed to a determinate state. PINHEAD (PNH) is expressed in the central domain of the developing plant: the provascular tissue, the shoot apical meristem, and the adaxial (upper) sides of lateral organ primordia. Here, we show that ectopic expression of PNH on the abaxial (lower) sides of lateral organs results in upward curling of leaf blades. This phenotype correlates with a loss of cell number coordination between the two surfaces of the blade, indicating that ectopic PNH can cause changes in cell division rates. More strikingly, moving PNH expression from the central to the peripheral domain of the embryo causes transformation of the determinate cotyledon axis to an indeterminate state. We propose that growth axes are specified as determinate versus indeterminate in a PNH-mediated step. Our results add to a growing body of evidence that radial positional information is important in meristem formation. These results also indicate that genes regulating cell division and axis determinacy are likely to be among PNH targets.