At the boundary between biological and cultural evolution: the origin of surname distributions

Surnames and non-recombining alleles are inherited from a single parent in a highly similar way. A simple birth-death model with mutations can accurately describe this process. Exponentially growing and constant populations are investigated, and we study how different compositions of the founder populations can be observed in present-day diversity distributions. We analyse different quantities in the statistically stationary state, both through analytic and numerical methods. Our results compare favourably to field data for family sizes in several countries. We discuss the relationship between the distribution of surnames and the genetic diversity of a population.     

The plant host Brassica napus induces in the pathogen Verticillium longisporum the expression of functional catalase peroxidase which is required for the late phase of disease

The devastating soilborne fungal pathogen Verticillium longisporum is host specific to members of the family Brassicaceae, including oilseed rape (Brassica napus) as the economically most important crop. The fungus infects through the roots and causes stunting and early senescence of susceptible host plants and a marked decrease in crop yield. We show here that V. longisporum reacts to the presence of B. napus xylem sap with the production of six distinct upregulated and eight downregulated proteins visualized by two-dimensional gel electrophoresis. Identification of 10 proteins by mass spectrometry revealed that all upregulated proteins are involved in oxidative stress response. The V. longisporum catalase peroxidase (VlCPEA) was the most upregulated protein and is encoded by two isogenes, VlcpeA-1 and VlcpeA-2. Both genes are 98% identical, corroborating the diploid or "amphihaploid" status of the fungus. Knock downs of both VlcpeA genes reduced protein expression by 80% and resulted in sensitivity against reactive oxygen species. Whereas saprophytic growth and the initial phase of the plant infection were phenotypically unaffected, the mutants were not able to perform the late phases of disease. We propose that the catalase peroxidase plays a role in protecting the fungus from the oxidative stress generated by the host plant at an advanced phase of the disease.     

Mechanistic studies of S-nitrosothiol formation by NO*/O2 and by NO*/methemoglobin

The mechanisms of formation of S-nitrosothiols under physiological conditions and, in particular, of generation of SNO-Hb (the hemoglobin form in which the cysteine residues beta93 are S-nitrosated) are still not completely understood. In this paper, we investigated whether, in the presence of O2, NO* is more efficient to nitrosate protein-bound thiols such as Cysbeta93 or low molecular weight thiols such as glutathione. Our results show that when substoichiometric amounts of NO* are mixed slowly with the protein solution, NO*, O2, and possibly NO2* and/or N2O3 accumulate in hydrophobic pockets of hemoglobin. Since the environment of the cysteine residue beta93 is rather hydrophobic, these conditions facilitate SNO-Hb production. Moreover, we show that S-nitrosation mediated by reaction of NO* with the iron(III) forms of Hb or Mb is significantly more effective when it can take place intramolecularly, as in metHb. Intermolecular reactions lead to lower S-nitrosothiol yields because of the concurring hydrolysis to nitrite.     

Co- and posttranslational modification of the alpha(1B)-adrenergic receptor: effects on receptor expression and function

We have characterized the maturation, co- and posttranslational modifications, and functional properties of the alpha(1B)-adrenergic receptor (AR) expressed in different mammalian cells transfected using conventional approaches or the Semliki Forest virus system. We found that the alpha(1B)-AR undergoes N-linked glycosylation as demonstrated by its sensitivity to endoglycosidases and by the effect of tunicamycin on receptor maturation. Pulse-chase labeling experiments in BHK-21 cells demonstrate that the alpha(1B)-AR is synthesized as a 70 kDa core glycosylated precursor that is converted to the 90 kDa mature form of the receptor with a half-time of approximately 2 h. N-Linked glycosylation of the alpha(1B)-AR occurs at four asparagines on the N-terminus of the receptor. Mutations of the N-linked glycosylation sites did not have a significant effect on receptor function or expression. Surprisingly, receptor mutants lacking N-linked glycosylation migrated as heterogeneous bands in SDS-PAGE. Our findings demonstrate that N-linked glycosylation and phosphorylation, but not palmitoylation or O-linked glycosylation, contribute to the structural heterogeneity of the alpha(1B)-AR as it is observed in SDS-PAGE. The modifications found are similar in the different mammalian expression systems explored. Our findings indicate that the Semliki Forest virus system can provide large amounts of functional and fully glycosylated alpha(1B)-AR protein suitable for biochemical and structural studies. The results of this study contribute to elucidate the basic steps involved in the processing of G protein-coupled receptors as well as to optimize strategies for their overexpression.     

Analysis of the kefA2 mutation suggests that KefA is a cation-specific channel involved in osmotic adaptation in Escherichia coli

Mechanosensitive channels play an essential role in the regulation of turgor pressure in bacteria. In Escherichia coli, there are multiple mechanosensitive channels that have been characterized genetically: MscL, YggB and KefA. In this report, we describe the cloning of the kefA gene, the organization of the KefA protein and the phenotype of a missense mutation, kefA, which affects the KefA mechanosensitive channel. The altered function of the channel is manifest through increased sensitivity to K+ during growth at low osmolarity and complete inhibition of growth in media containing high K+ concentrations (0.6 M) in the presence of betaine or proline. Growth in high Na+ medium (0.6 M NaCl plus 20 mM K+) is normal. Analysis of the cytoplasmic pools shows that the mutant cannot regulate the K+ content of the cytoplasm when grown in high K+ medium. However, regulation of pools of amino acids is essentially normal and the mutant can accumulate high pools of proline during growth inhibition. The mutant shows increased sensitivity to acid hypo-osmotic shock (transition from neutral to acid pH combined with a reduction in osmolarity). The data are consistent with abnormal regulation of KefA in the presence of high K+ concentrations and either betaine or proline.     

Pseudomonas putida and Pseudomonas fluorescens Species Group Recovery from Human Homes Varies Seasonally and by Environment

By shedding light on variation in time as well as in space, long-term biogeographic studies can help us define organisms’ distribution patterns and understand their underlying drivers. Here we examine distributions of Pseudomonas in and around 15 human homes, focusing on the P. putida and P. fluorescens species groups. We describe recovery from 10,941 samples collected during up to 8 visits per home, occurring on average 2.6 times per year. We collected a mean of 141 samples per visit, from sites in most rooms of the house, from the surrounding yards, and from human and pet occupants. We recovered Pseudomonas in 9.7% of samples, with the majority of isolates being from the P. putida and P. fluorescens species groups (approximately 62% and 23% of Pseudomonas samples recovered respectively). Although representatives of both groups were recovered from every season, every house, and every type of environment sampled, recovery was highly variable across houses and samplings. Whereas recovery of P. putida group was higher in summer and fall than in winter and spring, P. fluorescens group isolates were most often recovered in spring. P. putida group recovery from soils was substantially higher than its recovery from all other environment types, while higher P. fluorescens group recovery from soils than from other sites was much less pronounced. Both species groups were recovered from skin and upper respiratory tract samples from healthy humans and pets, although this occurred infrequently. This study indicates that even species that are able to survive under a broad range of conditions can be rare and variable in their distributions in space and in time. For such groups, determining patterns and causes of stochastic and seasonal variability may be more important for understanding the processes driving their biogeography than the identity of the types of environments in which they can be found.