Recurrent gene loss correlates with the evolution of stomach phenotypes in gnathostome history

The stomach, a hallmark of gnathostome evolution, represents a unique anatomical innovation characterized by the presence of acid- and pepsin-secreting glands. However, the occurrence of these glands in gnathostome species is not universal; in the nineteenth century the French zoologist Cuvier first noted that some teleosts lacked a stomach. Strikingly, Holocephali (chimaeras), dipnoids (lungfish) and monotremes (egg-laying mammals) also lack acid secretion and a gastric cellular phenotype. Here, we test the hypothesis that loss of the gastric phenotype is correlated with the loss of key gastric genes. We investigated species from all the main gnathostome lineages and show the specific contribution of gene loss to the widespread distribution of the agastric condition. We establish that the stomach loss correlates with the persistent and complete absence of the gastric function gene kit—H⁺/K⁺-ATPase (Atp4A and Atp4B) and pepsinogens (Pga, Pgc, Cym)—in the analysed species. We also find that in gastric species the pepsinogen gene complement varies significantly (e.g. two to four in teleosts and tens in some mammals) with multiple events of pseudogenization identified in various lineages. We propose that relaxation of purifying selection in pepsinogen genes and possibly proton pump genes in response to dietary changes led to the numerous independent events of stomach loss in gnathostome history. Significantly, the absence of the gastric genes predicts that reinvention of the stomach in agastric lineages would be highly improbable, in line with Dollo''s principle.     

Sodium nitroprusside enhances callus induction and shoot regeneration in high value medicinal plant Canscora diffusa

Plant Cell, Tissue and Organ Culture (PCTOC) - In different countries, mostly in EU, rules for strawberry nursery propagation impose the use of micropropagation only to produce stock virus free...     

Understanding dynamics using sensitivity analysis: caveat and solution

Background  

Parametric sensitivity analysis (PSA) has become one of the most commonly used tools in computational systems biology, in which the sensitivity coefficients are used to study the parametric dependence of biological models. As many of these models describe dynamical behaviour of biological systems, the PSA has subsequently been used to elucidate important cellular processes that regulate this dynamics. However, in this paper, we show that the PSA coefficients are not suitable in inferring the mechanisms by which dynamical behaviour arises and in fact it can even lead to incorrect conclusions.     

The Role of Carboxy-Terminal Glycosaminoglycan-binding Domain of Vitronectin in Cytoskeletal Organization and Migration of Endothelial Cells

Vitronectin is a major cell adhesion molecule present in the subendothelial matrix that mediates the attachment and spreading of a variety of cells. The carboxy-terminal end of vitronectin has a consensus sequence for glycosaminoglycan-binding. To define the functional role of this domain, we generated fragments of vitronectin that lack the glycosaminoglycan-binding domain by formic acid cleavage of plasma-derived vitronectin. In addition, we also generated similar recombinant fragments of vitronectin as glutathione S-transferase fusion proteins in E. coll. These fragments were tested for their ability to support the adhesion of human umbilical vein endothelial cells. These fragments promoted endothelial cell adhesion, reaching half maximal activity at 2-5 μg/well compared to plasma-derived vitronectin which reached at 0.2 μg/well. However, the cells that adhered to these fragments did not develop well-formed focal adhesion plaques and actin stress fibers. In addition, these fragments were poorly chemotactic for endothelial cell migration when compared to intact plasma-derived vitronectin in a modified Boyden chamber assay. The present studies show that carboxy-terminal glycosaminoglycan-binding domain of vitronectin is essential for proper cytoskeletal organization and migration of endothelial cells on vitronectin substratum.     

Metabolic flux analysis of lactic acid fermentation: effects of pH and lactate ion concentration

A detailed metabolic flux analysis for lactic acid production by Streptococcus lactis has been carried out. A metabolic reaction set was constructed for the metabolism of S. lactis. Fluxes through these reactions were estimated by using accumulation rates of biomass, product and consumption rates of the substrate, which were obtained through experiments. The changes in the flux movement are shown for different pHs and initial lactate concentrations of the medium. The analysis indicated that pH only affected the uptake rates of lactose, whereas lactate ion concentration influenced the movement of flux through the network.