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Abstract Background Chromatin provides a tunable platform for gene expression control. Besides the well-studied core nucleosome, H1 linker histones are abundant chromatin components with intrinsic potential to influence chromatin function. Well studied in animals, little is known about the evolution of H1 function in other eukaryotic lineages for instance plants. Notably, in the model plant Arabidopsis, while H1 is known to influence heterochromatin and DNA methylation, its contribution to transcription, molecular, and cytological chromatin organization remains elusive. Results We provide a multi-scale functional study of Arabidopsis linker histones. We show that H1-deficient plants are viable yet show phenotypes in seed dormancy, flowering time, lateral root, and stomata formation—complemented by either or both of the major variants. H1 depletion also impairs pluripotent callus formation. Fine-scale chromatin analyses combined with transcriptome and nucleosome profiling reveal distinct roles of H1 on hetero- and euchromatin: H1 is necessary to form heterochromatic domains yet dispensable for silencing of most transposable elements; H1 depletion affects nucleosome density distribution and mobility in euchromatin, spatial arrangement of nanodomains, histone acetylation, and methylation. These drastic changes affect moderately the transcription but reveal a subset of H1-sensitive genes. Conclusions H1 variants have a profound impact on the molecular and spatial (nuclear) chromatin organization in Arabidopsis with distinct roles in euchromatin and heterochromatin and a dual causality on gene expression. Phenotypical analyses further suggest the novel possibility that H1-mediated chromatin organization may contribute to the epigenetic control of developmental and cellular transitions.

We estimate the elasticity of substitution between high-skill and low-skill workers using panel data from 32 countries during 1970–2015. Most existing estimates, which are based only on US microdata, find a value close to 1.6. We bring international data together with a theory-informed macro-approach to provide new evidence on this important macroeconomic parameter. Using the macro-approach, we find that the elasticity of substitution between tertiary-educated workers and those with lower education levels falls between 1.7 and 2.6, which is higher than previous estimates but within a plausible range. In some specifications, estimated elasticity is above the value required for strong skill-bias of technology, suggesting strong skill-bias is possible. [ABSTRACT FROM AUTHOR]

Linker histones (H1s) are conserved and ubiquitous structural components of eukaryotic chromatin. Multiple non-allelic variants of H1, which differ in their DNA/nucleosome binding properties, co-exist in animal and plant cells and have been implicated in the control of genetic programs during development and differentiation. Studies in mammals and Drosophila have revealed diverse post-translational modifications of H1s, most of which are of unknown function. So far, it is not known how this pattern compares with that of H1s from other major lineages of multicellular Eukaryotes. Here, we show that the two main H1variants of a model flowering plant Arabidopsis thaliana are subject to a rich and diverse array of post-translational modifications. The distribution of these modifications in the H1 molecule, especially in its globular domain (GH1), resembles that occurring in mammalian H1s, suggesting that their functional significance is likely to be conserved. While the majority of modifications detected in Arabidopsis H1s, including phosphorylation, acetylation, mono- and dimethylation, formylation, crotonylation and propionylation, have also been reported in H1s of other species, some others have not been previously identified in histones.

As continuation of investigations in to the mechanism of the role of the H1 histone, which is a crucial protein component chromosomes of all eukaryotes, transgenic tobacco plants with different levels of the H1 histone variants were examined. Tobacco has six sequential variants of the H1 histone: two major ones (H1A and H1B), constituting ca. 90% of all H1, and four minor ones (H1C, H1D, H1E and H1F), occurring in very small quantities. The following groups of plants were examined: K - control group with a full set of histone variants; -AB -with the A and B variants removed; -ABCD - with the A, B, C and D variants removed; and -CD - with the C and D variants removed. The analysis of microsporogenesis in those plants, based on preparations squeezed in acetoorcein, revealed the asynchronous course of meiosis in -AB and -ABCD plants, occurrence of chromosomal aberration, and, consequently, the formation of sterile pollen grains (accordingly: 84,4% and 81,4%). In -CD plants, the percentage of aberration and sterile pollen grains was similar to the control material. Electron microscope observations of microsporogenesis showed ultrastructural changes. In -AB and -ABCD plants, a major portion of the pollen grains were degraded. The smallest number of degraded pollen grains, in comparison with the control, was found in the -CD group.

The phenomenon of male sterility has often been observed in investigations on the role of histone H1 in regulation of morphogenetic and cytological processes in transgenic tobacco plants. These changes were accumulated by disturbances in flower development, consisting in lengthening of the pistil style in relation to stamen heads. This prevented pollination and production of seeds. As similar abnormalities occurred also in the present investigations (depending on combination, the sterility% was 84.4 to 19.9, at only 8.1 in the control), the main problem of our investigations was an attempt to explain their reasons. It is commonly known that one of the conditions for formation of fertile pollen is the properly functioning tapetum. Here, we carried out observations of ultrastructure of anther tapetum control cells in respect of abnormalities which occurred during microsporogenesis of transgenic plants with inactivated expression of two major (A, B) and two minor (C, D) histone H1 variants. The investigations were carried out on the following groups of plants: (1) control group with a full set of histone variants (K), (2) with inactivated A and B variants (-AB); (3) with inactivated A, B, C and D variants (-ABCD), (4) with inactivated C and D variants (-CD). It was found that tapetal development was normal in all the investigated groups of plants, and the sequence of changes was similar as in the control. However, certain ultrastructural differences appeared when tapetum functioned as secretory tissue, and in the degeneration phase. In tapetal cell cytoplasm, with participation of rER, lipid bodies were formed, which, having penetrated to the cell surface and to locules, took part in formation of pollen grain sporoderm. Both in the control and in the remaining combination, excluding -ABCD, these bodies looked similar: they were grey, homogenous and surrounded by black jagged deposits. In -ABCD plants, these bodies were more translucent, slightly rarefied, and not surrounded by the deposits. Moreover, in -CD plants, large lipid deposits were frequently observed between remainders of degraded tapetal cells. They did not occur in the control and the remaining combinations.

We argue that financial market development contributed to the rise in the skill premium and residual wage inequality in the United States since the 1980s. We present an endogenous growth model with imperfect credit markets and establish how improving the efficiency of these markets affects modes of production, innovation, and wage dispersion between skilled and unskilled workers. The experience of U.S. states following banking deregulation provides empirical support for our hypothesis. We find that wages of skilled workers increased by between 0.5% and 6.3% following deregulation while those of unskilled workers fell by between 3.5% and 8. 7%. Similarly, residual (or within-group) inequality increased; the 90-50 percentile ratio of residuals from a Mincerian wage regression and their standard deviation increased by 4.2% and 1.7%, respectively. (JEL E25, J31, G24), I. INTRODUCTION In recent years, the increase in wage inequality in the United States has received a lot of attention from economists. Researchers have documented the rise since the 1980s [...]

SWI/SNF chromatin remodeling complexes perform a pivotal function in the regulation of eukaryotic gene expression. Arabidopsis (Arabidopsis thaliana) mutants in major SWI/SNF subunits display embryo-lethal or dwarf phenotypes, indicating their critical role in molecular pathways controlling development and growth. As gibberellins (GA) are major positive regulators of plant growth, we wanted to establish whether there is a link between SWI/SNF and GA signaling in Arabidopsis. This study revealed that in brm-1 plants, depleted in SWI/SNF BRAHMA (BRM) ATPase, a number of GA-related phenotypic traits are GA-sensitive and that the loss of BRM results in markedly decreased level of endogenous bioactive GA. Transcriptional profiling of brm-1 and the GA biosynthesis mutant ga1-3, as well as the ga1-3/brm-1 double mutant demonstrated that BRM affects the expression of a large set of GA-responsive genes including genes responsible for GA biosynthesis and signaling. Furthermore, we found that BRM acts as an activator and directly associates with promoters of GA3ox1, a GA biosynthetic gene, and SCL3, implicated in positive regulation of the GA pathway. Many GA-responsive gene expression alterations in the brm-1 mutant are likely due to depleted levels of active GAs. However, the analysis of genetic interactions between BRM and the DELLA GA pathway repressors, revealed that BRM also acts on GA-responsive genes independently of its effect on GA level. Given the central position occupied by SWI/SNF complexes within regulatory networks controlling fundamental biological processes, the identification of diverse functional intersections of BRM with GA-dependent processes in this study suggests a role for SWI/SNF in facilitating crosstalk between GA-mediated regulation and other cellular pathways.

Recent development and growth accounting studies have established that total factor productivity is an important source of cross-country differences in income levels and growth rates. This paper makes two contributions. First, it examines the sensitivity of the development accounting results to the Cobb-Douglas specification of the production function. Second, within the Cobb-Douglas framework, it weighs evidence of the two alternative explanations of total factor productivity differences: the inefficiency view and the appropriate technology view. To accomplish these tasks, the world production frontier is estimated using a nonparametric deterministic approach known as data envelopment analysis. I find that the fraction of income differences explained by physical and human capital increases from 32% to 55% when departing from the Cobb-Douglas assumption. There is also evidence consistent with the appropriate technology view; countries with an inadequate mix of inputs are unable to access the most productive technologies. Moreover, the world technology frontier appears to be shifting out faster at input combinations close to that of the R&D leader. However, inefficiency appears to be the main explanation for low incomes throughout the world; it explains 43% of output variation in 1995, and its importance has increased over time. JEL classification: E23; O11; O33; O47 Keywords: TFP differences; Development accounting; Efficiency; Appropriate technology

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jdeveco.2005.05.005 Byline: MichaA Jerzmanowski Keywords: Economic growth; Regime switching; Convergence; Institutions Abstract: Most economic growth research has been aimed at explaining cross-country differences in average growth rates. However, it is well known that growth experiences differ over time within a country almost as much as they differ among countries. This paper builds on Pritchett's (2000) [Pritchett, Lant, Understanding patterns of economic growth: searching for hills among plateaus, mountains, and plains, World Bank Economic Review, May 2000, 14 (2), 221-250.] observation that the growth process can be thought of as transitions between different growth regimes and proposes a framework for systematic analysis of such regimes and the dynamics of the transitions. I estimate a Markov-switching regression to characterize four distinct growth regimes and transitions between them. The results show that countries switch among regimes of stable growth, 'miracle' catch-up, stagnation and crisis with the transition probabilities determined by the quality of institutions. Better institutions appear to improve long-run growth by making episodes of fast growth more persistent. Low average growth rates in countries with weak institutions are a result of these countries spending more time in stagnation regimes rather then being incapable of fast growth at all. Weak institutions do not rule out growth takeoffs but limit their sustainability. The approach directs attention to shifts in growth performance and highlights the fact that identical average growth rates can mask very distinct growth paths. Author Affiliation: The John E. Walker Department of Economics, Clemson University, United States Article History: Received 26 February 2004; Revised 11 May 2005; Accepted 21 May 2005 Article Note: (footnote) [star] I am especially indebted to David Weil for his advice and insightful suggestions. I also benefited from many helpful comments by Oded Galor, Peter Howitt, Sean Campbell, Len Erickson, two anonymous referees, and the editor, Lant Pritchett. All errors are my own.