Decreased p53 is associated with a decline in asymmetric stem cell self‐renewal in aged human epidermis

With age, the epidermis becomes hypoplastic and hypoproliferative. Hypoproliferation due to aging has been associated with decreased stem cell (SC) self‐renewal in multiple murine tissues. The fate of SC self‐renewal divisions can be asymmetric (one SC, one committed progenitor) or symmetric (two SCs). Increased asymmetric SC self‐renewal has been observed in inflammatory‐mediated hyperproliferation, while increased symmetric SC self‐renewal has been observed in cancers. We analyzed SC self‐renewal divisions in aging human epidermis to better understand the role of SCs in the hypoproliferation of aging. In human subjects, neonatal to 78 years, there was an age‐dependent decrease in epidermal basal layer divisions. The balance of SC self‐renewal shifted toward symmetric SC self‐renewal, with a decline in asymmetric SC self‐renewal. Asymmetric SC divisions maintain epidermal stratification, and this decrease may contribute to the hypoplasia of aging skin. P53 decreases in multiple tissues with age, and p53 has been shown to promote asymmetric SC self‐renewal. Fewer aged than adult ALDH+CD44+ keratinocyte SCs exhibited p53 expression and activity and Nutlin‐3 (a p53 activator) returned p53 activity as well as asymmetric SC self‐renewal divisions to adult levels. Nutlin‐3 increased Notch signaling (NICD, Hes1) and DAPT inhibition of Notch activation prevented Nutlin‐3 (p53)‐induced asymmetric SC self‐renewal divisions in aged keratinocytes. These studies indicate a role for p53 in the decreased asymmetric SC divisions with age and suggest that in aged keratinocytes, Notch is required for p53‐induced asymmetric SC divisions.     

LrrkA,a kinase with leucine‐rich repeats,links folate sensing with Kil2 activity and intracellular killing

Phagocytic cells ingest bacteria by phagocytosis and kill them efficiently inside phagolysosomes. The molecular mechanisms involved in intracellular killing and their regulation are complex and still incompletely understood. Dictyostelium discoideum has been used as a model to discover and to study new gene products involved in intracellular killing of ingested bacteria. In this study, we performed random mutagenesis of Dictyostelium cells and isolated a mutant defective for growth on bacteria. This mutant is characterized by the genetic inactivation of the lrrkA gene, which encodes a protein with a kinase domain and leucine‐rich repeats. LrrkA knockout (KO) cells kill ingested Klebsiella pneumoniae bacteria inefficiently. This defect is not additive to the killing defect observed in kil2 KO cells, suggesting that the function of Kil2 is partially controlled by LrrkA. Indeed, lrrkA KO cells exhibit a phenotype similar to that of kil2 KO cells: Intraphagosomal proteolysis is inefficient, and both intraphagosomal killing and proteolysis are restored upon exogenous supplementation with magnesium ions. Bacterially secreted folate stimulates intracellular killing in Dictyostelium cells, but this stimulation is lost in cells with genetic inactivation of kil2, lrrkA, or far1. Together, these results indicate that the stimulation of intracellular killing by folate involves Far1 (the cell surface receptor for folate), LrrkA, and Kil2. This study is the first identification of a signalling pathway regulating intraphagosomal bacterial killing in Dictyostelium cells.     

The Episode of Genetic Drift Defining the Migration of Humans out of Africa Is Derived from a Large East African Population Size

Human genetic variation particularly in Africa is still poorly understood. This is despite a consensus on the large African effective population size compared to populations from other continents. Based on sequencing of the mitochondrial Cytochrome C Oxidase subunit II (MT-CO2), and genome wide microsatellite data we observe evidence suggesting the effective size (Ne) of humans to be larger than the current estimates, with a foci of increased genetic diversity in east Africa, and a population size of east Africans being at least 2-6 fold larger than other populations. Both phylogenetic and network analysis indicate that east Africans possess more ancestral lineages in comparison to various continental populations placing them at the root of the human evolutionary tree. Our results also affirm east Africa as the likely spot from which migration towards Asia has taken place. The study reflects the spectacular level of sequence variation within east Africans in comparison to the global sample, and appeals for further studies that may contribute towards filling the existing gaps in the database. The implication of these data to current genomic research, as well as the need to carry out defined studies of human genetic variation that includes more African populations; particularly east Africans is paramount.     

Genetic organization and sequence of the rfb gene cluster of Yersinia enterocolitica serotype O:3: similarities to the dTDP-L-rhamnose biosynthesis pathway of Salmonella and to the bacterial polysaccharide transport systems

The Yersinia enterocolitica O:3 lipopotysaccharide O-antigen is a homopotymer of 6-deoxy-L-altrose. The cloned rfb region was sequenced, and 10 open reading frames were identified. Transposon mutagenesis, deletion analysis and transcomplementatton experiments showed that eight of the genes, organized into two operons, rfbABC and rfbDEFGH, are essential for 0-antigen synthesis. Functional tandem promoters were identified upstream of both operons. Of the deduced polypeptides RfbA, RfbF and RfbG were similar to Salmonella proteins involved in the dTDP-l -rhamnose biosynthesis. Rhamnose and 6-deoxy-l -altrose are C3-epimers suggesting that analogous pathways function in their biosynthesis. RfbD and RfbE were similar to capsular polysaccharide export proteins, e.g. KpsM and KpsT of Escherichia coli. This and transposon mutagenesis showed that RfbD and RfbE function as O-antigen exporters.     

Estimation of Genetic Divergence and Character Association Studies in Local and Exotic Diversity Panels of Soybean (<i>Glycine max</i> L.) Genotypes

The availability of favorable genetic diversity is a thriving vitality for the success of a breeding program. It provides a firm basis of selecting superior breeding lines for the development of high yielding crop genotypes. In this context, present investigation aimed to generate information on genetic divergence and character association in a diversity panel of 123 local and exotic soybean genotypes. Analysis of variance revealed significant response of the evaluated genotypes based on studied attributes. It depicted the probability of selecting desirable soybean genotypes by focusing on character association studies and genetic diversity analysis. Correlation analysis revealed that seed yield per plant showed high positive correlation with 100-seed weight followed by pods per plant and plant height. Furthermore, path coefficient analysis exposed that pods per plant had maximum direct contribution in seed yield per plant followed by 100-seed weight, days to flowering and SPAD measurement. Genotype named “G-10” showed maximum yield per plant followed by 24607, G-52, 24593, Arisoy, 24566, 17426, A-3127, 24570 and 24567. Genetic diversity analysis grouped the evaluated germplasm into 17 clusters. All clusters showed zero intra-cluster variability; while inter-cluster divergence ranged from 9.00 to 91.11. Cluster V showed maximum inter-cluster distance with cluster XII followed by that of between V and VIII. Moreover, cluster IV with superior genotypes (G-10, 24607, 24593 and 24566), VI (17426 and 24567), XIII (24570) and X (Arisoy and G-52) showed above mean values for most of the studied characters. Overall, the results of hybridization between the superior genotypes of these cluster pairs might be useful for soybean breeding with improving agronomic traits and adaptability.     

Confirmation and quantification of strigolactones, germination stimulants for root parasitic plants Striga and Orobanche, produced by cotton

The germination stimulants for root parasitic plants Striga and Orobanche produced by cotton (Gossypium hirsutum L.) were examined in detail. Seeds of cotton were germinated and grown on glass wool wetted with sterile distilled water in sterile filter units. The root exudate was collected daily and extracted with ethyl acetate. Each of these ethyl acetate extracts was analyzed directly by high-performance liquid chromatography linked with tandem mass spectrometry (LC/MS/MS). The results demonstrate that cotton roots exuded strigol and strigyl acetate, but no other known strigolactones such as orobanchol and alectrol. The production of strigol was detected even in the root exudate collected during the first 24 h of incubation and reached a maximum 5-7 days later. The average exudation of strigol and strigyl acetate during the incubation period was ca. 15 and 2 pg/plant/day, respectively, indicating that strigol mainly contributed to germination stimulation by the cotton root exudate.     

Detoxification of the organophosphate nerve agent coumaphos using organophosphorus hydrolase immobilized on cellulose materials

Neurotoxic organophosphates (OPs) are widely used as pesticides and for public health purposes, as well as being nerve gases. As a result of the widespread use of these compounds for agriculture, large volumes of wastewater are generated. Additionally, there are large stockpiles of the nerve gases soman, sarin and VX in the United States and elsewhere around the world. Organophosphorus hydrolase (OPH) is an enzyme that catalyzes the hydrolysis of OP nerve agents. To date, however, the use of this enzyme in detoxification processes has been rather limited due to the high cost of its purification and short catalytic half-life. This paper reports the development of a cost-effective method for the production and immobilization of OPH in a pilot application in an enzyme bioreactor column for detoxification of paraoxon and coumaphos in contaminated wastewaters. A fusion between OPH and a cellulose binding domain that binds selectively to cellulose was generated to allow one-step purification and immobilization of OPH on cheap and abundantly available cellulose immobilization matrices. When packed in a column bioreactor, the immobilized fusion enzyme was able to completely degrade coumaphos up to a concentration of 0.2 mM. However, stirring of OPH immobilized on cellulose materials resulted in complete OP degradation of 1.5 mM coumaphos. The bioreactor column degraded the compounds tested at high concentration, rapidly, and without loss of process productivity for about 2 months.