Maize domestication from teosinte (Zeamays ssp. parviglumis) was accompanied by an increase of kernel size in landraces. Subsequent breeding has led to a diversification of kernel size
and starch content among major groups of inbred lines. We aim at investigating the effect of domestication on duplicated genes
encoding a key enzyme of the starch pathway, the ADP-glucose pyrophosphorylase (AGPase). Three pairs of paralogs encode the
AGPase small (SSU) and large (LSU) subunits mainly expressed in the endosperm, the embryo and the leaf. We first validated
the putative sequence of LSUleaf through a comparative expression assay of the six genes. Second, we investigated the patterns of molecular evolution on a
2 kb coding region homologous among the six genes in three panels: teosintes, landraces, and inbred lines. We corrected for
demographic effects by relying on empirical distributions built from 580 previously sequenced ESTs. We found contrasted patterns
of selection among duplicates: three genes exhibit patterns of directional selection during domestication (SSUend, LSUemb) or breeding (LSUleaf), two exhibit patterns consistent with diversifying (SSUleaf) and balancing selection (SSUemb) accompanying maize breeding. While patterns of linkage disequilibrium did not reveal sign of coevolution between genes expressed
in the same organ, we detected an excess of non-synonymous substitutions in the small subunit functional domains highlighting
their role in AGPase evolution. Our results offer a different picture on AGPase evolution than the one depicted at the Angiosperm
level and reveal how genetic redundancy can provide flexibility in the response to selection. 相似文献
The effect of repair techniques on the biomechanics of the aorta is poorly understood, resulting in significant levels of postoperative complications for patients worldwide. This study presents a computational analysis of the influence of Nitinol-based devices on the biomechanical performance of a healthy patient-specific human aorta. Simulations reveal that Nitinol stent-grafts stretch the artery wall so that collagen is stretched to a straightened high-stiffness configuration. The high-compliance regime (HCR) associated with low diastolic lumen pressure is eliminated, and the artery operates in a low-compliance regime (LCR) throughout the entire cardiac cycle. The slope of the lumen pressure–area curve for the LCR post-implantation is almost identical to that of the native vessel during systole. This negligible change from the native LCR slope occurs because the stent-graft increases its diameter from the crimped configuration during deployment so that it reaches a low-stiffness unloading plateau. The effective radial stiffness of the implant along this unloading plateau is negligible compared to the stiffness of the artery wall. Provided the Nitinol device unloads sufficiently during deployment to the unloading plateau, the degree of oversizing has a negligible effect on the pressure–area response of the vessel, as each device exerts approximately the same radial force, the slope of which is negligible compared to the LCR slope of the native artery. We show that 10% oversizing based on the observed diastolic diameter in the mid descending thoracic aorta results in a complete loss of contact between the device and the wall during systole, which could lead to an endoleak and stent migration. 20% oversizing reaches the Dacron enforced area limit (DEAL) during the pulse pressure and results in an effective zero-compliance in the later portion of systole.
Why is the genetic code the way it is? Concepts from fields as diverse as molecular evolution, classical chemistry, biochemistry and metabolism have been used to define selection pressures most likely to be involved in the shaping of the genetic code. 相似文献
Formerly known as a hypoendemic malaria country, the Republic of Djibouti declared the goal of pre-eliminating malaria in 2006. The aim of the present study was to evaluate the prevalence of Plasmodium falciparum, Plasmodium vivax and mixed infections in the Djiboutian population by using serological tools and to identify potential determinants of the disease and hotspots of malaria transmission within the country. The prevalence of P. falciparum and P. vivax within the districts of the capital city and the rest of the Republic of Djibouti were assessed using 13 and 2 serological markers, respectively. The relationship between the immune humeral response to P. falciparum and P. vivax and variables such as age, gender, wealth status, urbanism, educational level, distance to rivers/lakes, living area, having fever in the last month, and staying in a malaria-endemic country more than one year was estimated and analysed by questionnaires administered to 1910 Djiboutians. Multivariate ordinal logistic regression models of the immune humeral response were obtained for P. falciparum and P. vivax. The P. falciparum and P. vivax seroprevalence rates were 31.5%, CI95% [29.4-33.7] and 17.5%, CI95% [15.8-19.3], respectively. Protective effects against P. falciparum and P. vivax were female gender, educational level, and never having visited a malaria-endemic area for more than one year. For P. falciparum only, a protective effect was observed for not having a fever in the last month, living more than 1.5 km away from lakes and rivers, and younger ages. This is the first study that assessed the seroprevalence of P. vivax in the Republic of Djibouti. It is necessary to improve knowledge of this pathogen in order to create an effective elimination programme. As supported by recent observations on the subject, the Republic of Djibouti has probably demonstrated a real decrease in the transmission of P. falciparum in the past seven years, which should encourage authorities to improve efforts toward elimination. 相似文献
Sophisticated molecular biological research has revealed many virulence attributes in at least four pathogenic fungi, but the future study of fungal virulence requires investigators to distinguish between molecules that directly interact with the host, molecules that regulate these, and molecules that are always required for fungal growth and survival, independent of the host. 相似文献
Although the morphological steps of maize (Zea mays) endosperm development are well described, very little is known concerning the coordinated accumulation of the numerous proteins involved. Here, we present a proteomic study of maize endosperm development. The accumulation pattern of 409 proteins at seven developmental stages was examined. Hierarchical clustering analysis allowed four main developmental profiles to be recognized. Comprehensive investigation of the functions associated with clusters resulted in a consistent picture of the developmental coordination of cellular processes. Early stages, devoted to cellularization, cell division, and cell wall deposition, corresponded to maximal expression of actin, tubulins, and cell organization proteins, of respiration metabolism (glycolysis and tricarboxylic acid cycle), and of protection against reactive oxygen species. An important protein turnover, which is likely associated with the switch from growth and differentiation to storage, was also suggested from the high amount of proteases. A relative increase of abundance of the glycolytic enzymes compared to tricarboxylic acid enzymes is consistent with the recent demonstration of anoxic conditions during starch accumulation in the endosperm. The specific late-stage accumulation of the pyruvate orthophosphate dikinase may suggest a critical role of this enzyme in the starch-protein balance through inorganic pyrophosphate-dependent restriction of ADP-glucose synthesis in addition to its usually reported influence on the alanine-aromatic amino acid synthesis balance. 相似文献
The Distributed Annotation System (DAS) is a network protocol for exchanging biological data. It is frequently used to share
annotations of genomes and protein sequence. 相似文献
Normalization is the process of removing non-biological sources of variation between array experiments. Recent investigations
of data in gene expression databases for varying organisms and tissues have shown that the majority of expressed genes exhibit
a power-law distribution with an exponent close to -1 (i.e. obey Zipf's law). Based on the observation that our single channel
and two channel microarray data sets also followed a power-law distribution, we were motivated to develop a normalization
method based on this law, and examine how it compares with existing published techniques. A computationally simple and intuitively
appealing technique based on this observation is presented. 相似文献