Permeability of cellophane membranes to parotid during dialysis

Comparative quantitative proteomics of osmotic signal transduction mutants in Botrytis cinerea explain mutant phenotypes and highlight interaction with cAMP and Ca2+ signalling pathways

Signal transduction (ST) is essential for rapid adaptive responses to changing environmental conditions. It acts through rapid post-translational modifications of signalling proteins and downstream effectors that regulate the activity and/or subcellular localisation of target proteins, or the expression of downstream genes. We have performed a quantitative, comparative proteomics study of ST mutants in the phytopathogenic fungus Botrytis cinerea during axenic growth under non-stressed conditions to decipher the roles of two kinases of the hyper-osmolarity pathway in B. cinerea physiology. We studied the mutants of the sensor histidine kinase Bos1 and of the MAP kinase Sak1. Label-free shotgun proteomics detected 2425 proteins, 628 differentially abundant between mutants and wild-type, 270 common to both mutants, indicating independent and shared regulatory functions for both kinases. Gene ontology analysis showed significant changes in functional categories that may explain in vitro growth and virulence defects of both mutants (secondary metabolism enzymes, lytic enzymes, proteins linked to osmotic, oxidative and cell wall stress). The proteome data also highlight a new link between Sak1 MAPK, cAMP and Ca²⁺ signalling. This study reveals the potential of proteomic analyses of signal transduction mutants to decipher their biological functions. TEXT-VULGARISATION: The fungus Botrytis cinerea is responsible for grey mold disease of hundreds of plant species. During infection, the fungus has to face important changes of its environment. Adaptation to these changing environmental conditions involves proteins of such called signal transduction pathways that regulate the production, activity or localisation of cellular components, mainly proteins. While the components of such signal transduction pathways are well known, their role globally understood, the precise impact on protein production remains unknown. In this study we have analysed and compared the global protein content of two Botrytis cinerea signal transduction mutants - both avirulent - to the pathogenic parental strain. The data of 628 differential proteins between mutants and wild-type, showed significant changes in proteins related to plant infection (secondary metabolism enzymes, lytic enzymes, proteins linked to osmotic, oxidative and cell wall stress) that may explain the virulence defects of both mutants. Moreover, we observed intracellular accumulation of secreted proteins in one of the mutants suggesting a potential secretion defect.

Parotid saliva protein profiles in caries-free and caries-active adults

OBJECTIVE

The objective of this study was to determine if there were any differences in the parotid saliva output and composition related to caries activity.

STUDY DESIGN

Stimulated parotid saliva samples were collected from 85 healthy young adults, caries-active or caries-free. Flow rates were determined, and samples were analyzed for pH and buffer capacity, total protein, electrolytes, proteins with a high performance liquid chromatography method, and histatins.

RESULTS

There were no differences in flow rates or pH, but buffer capacity was higher in women than in men, and K+ and Cl- were both slightly higher in the caries-active group. The women had a significantly higher total protein concentration, as well as higher concentrations of each of the individual protein components assayed. There were no differences attributable to caries activity.

CONCLUSIONS

Significant sex differences in salivary protein concentrations exist. Caries activity may be related to some salivary electrolyte alterations, but not to protein composition.

Evidence of microfilament-associated mitochondrial movement

The mitochondria in the lower Malpighian tubule of the insect Rhodnius prolixus can be stimulated by feeding in vivo and by 5-hydroxytryptamine in vitro, to move from a position below the cell cortex to one inside the apical microvilli. During and following their movement into the microvilli, the mitochondria are intimately associated with the microfilaments of the cell cortex and microvillar core bundle. Bridges approximately 14 nm in length and 4 nm in diameter are observed connecting the microvillar microfilaments to the outer mitochondrial membrane and microvillar plasma membrane. Depolymerization of all visible microtubules with colchicine does not inhibit 5-HT-stimulated mitochondrial movement. On the other hand, treatment with cytochalasin B does block mitochondrial movement, suggesting that microfilaments play a role in the mitochondrial motility. We have labeled the microvillar microfilaments, which are 6 nm in diameter, with heavy meromyosin, which supports the contention that they contain actin. A model of the mechanism of mitochondrial movement is presented in which mitochondria slide into position in the microvilli along actin-containing microfilaments in a manner analogous to the sliding actin-myosin model of skeletal muscle.