Genome-wide investigation reveals high evolutionary rates in annual model plants

<p>Abstract</p> <p>Background</p> <p>Rates of molecular evolution vary widely among species. While significant deviations from molecular clock have been found in many taxa, effects of life histories on molecular evolution are not fully understood. In plants, annual/perennial life history traits have long been suspected to influence the evolutionary rates at the molecular level. To date, however, the number of genes investigated on this subject is limited and the conclusions are mixed. To evaluate the possible heterogeneity in evolutionary rates between annual and perennial plants at the genomic level, we investigated 85 nuclear housekeeping genes, 10 non-housekeeping families, and 34 chloroplast genes using the genomic data from model plants including <it>Arabidopsis thaliana </it>and <it>Medicago truncatula </it>for annuals and grape (<it>Vitis vinifera</it>) and popular (<it>Populus trichocarpa</it>) for perennials.</p> <p>Results</p> <p>According to the cross-comparisons among the four species, 74-82% of the nuclear genes and 71-97% of the chloroplast genes suggested higher rates of molecular evolution in the two annuals than those in the two perennials. The significant heterogeneity in evolutionary rate between annuals and perennials was consistently found both in nonsynonymous sites and synonymous sites. While a linear correlation of evolutionary rates in orthologous genes between species was observed in nonsynonymous sites, the correlation was weak or invisible in synonymous sites. This tendency was clearer in nuclear genes than in chloroplast genes, in which the overall evolutionary rate was small. The slope of the regression line was consistently lower than unity, further confirming the higher evolutionary rate in annuals at the genomic level.</p> <p>Conclusions</p> <p>The higher evolutionary rate in annuals than in perennials appears to be a universal phenomenon both in nuclear and chloroplast genomes in the four dicot model plants we investigated. Therefore, such heterogeneity in evolutionary rate should result from factors that have genome-wide influence, most likely those associated with annual/perennial life history. Although we acknowledge current limitations of this kind of study, mainly due to a small sample size available and a distant taxonomic relationship of the model organisms, our results indicate that the genome-wide survey is a promising approach toward further understanding of the mechanism determining the molecular evolutionary rate at the genomic level.</p

Significant improvement of Jc in MgB2 bulk superconductor using ball-milled high-purity crystalline boron

The particle size, purity and form of the starting boron powders play an important role in the superconducting properties of MgB2. In this paper high-purity (99.999%) boron powders with crystalline phase that were processed by ball milling have been used as the precursor powders. It was observed that the critical current density (Jc) value was 9.1 x 103 A cm-2 at 5 K and 8 T, which is two times higher than for a sample with ball-milled amorphous boron powders, and a factor of 40 higher than a sample made from as-supplied amorphous boron powders. Significant Jc improvement at high fields is attributed to the Hc2 enhancement caused by the increased disorder

Regulating Extra-Framework Cations in Faujasite Zeolites for Capture of Trace Carbon Dioxide

The development of cost‐effective sorbents for direct capture of trace CO(2) (95 % dry CO(2) uptake can be preserved under relative humidity of 74 %. In situ solid‐state NMR spectroscopy, synchrotron X‐ray diffraction and neutron diffraction reveal two binding sites for CO(2) in these zeolites, namely the basic framework oxygen atoms and the divalent alkaline earth metal ions. This study unlocks the potential of low‐cost natural zeolites for applications in direct air capture