Detailed Analysis of a Contiguous 22-Mb Region of the Maize Genome

Most of our understanding of plant genome structure and evolution has come from the careful annotation of small (e.g., 100 kb) sequenced genomic regions or from automated annotation of complete genome sequences. Here, we sequenced and carefully annotated a contiguous 22 Mb region of maize chromosome 4 using an improved pseudomolecule for annotation. The sequence segment was comprehensively ordered, oriented, and confirmed using the maize optical map. Nearly 84% of the sequence is composed of transposable elements (TEs) that are mostly nested within each other, of which most families are low-copy. We identified 544 gene models using multiple levels of evidence, as well as five miRNA genes. Gene fragments, many captured by TEs, are prevalent within this region. Elimination of gene redundancy from a tetraploid maize ancestor that originated a few million years ago is responsible in this region for most disruptions of synteny with sorghum and rice. Consistent with other sub-genomic analyses in maize, small RNA mapping showed that many small RNAs match TEs and that most TEs match small RNAs. These results, performed on ∼1% of the maize genome, demonstrate the feasibility of refining the B73 RefGen_v1 genome assembly by incorporating optical map, high-resolution genetic map, and comparative genomic data sets. Such improvements, along with those of gene and repeat annotation, will serve to promote future functional genomic and phylogenomic research in maize and other grasses

Gamma and X-ray sensitivity of Gd\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e heterojunctions

We find that Gd2O3 thin films strongly favor a (-402) texture growth on a variety of substrates and will form heterojunction diodes with silicon, especially when doped with oxygen vacancies. Even in the thin film limit, these heterojunction diodes appear to be sensitive to gamma radiation, likely from the X-rays created by scattering events, adding to the numerous hurdles that must be overcome if Gd based semiconductor devices are to be used for solid state neutron detection applications

Absorption Induced by Mn Doping of ZnS for Improved Sensitized Quantum-Dot Solar Cells

ZnS quantum dots (QDs) have limited application potential in QD-sensitized solar cells because of their wide-band-gap, which does not allow absorption of sunlight in the visible and infrared regions. Introducing intermediate-energy levels in the QDs is one way to expand the absorption window into the visible region. We show that this effect is achieved in Mn-doped ZnS QDs. Mn-doped ZnS QDs are synthesized by laser ablation in water and solution-based methods. The structural, optical, and magnetic properties of the ZnS:Mn QDs are examined by x-ray diffraction (XRD), transmission electron microscope (TEM), photoluminescence (PL) emission, photoluminescence excitation (PLE), and magnetic susceptibility measurements. The average particle size of cubic phase ZnS:Mn estimated from the XRD and TEM is about 3 nm. The QDs show two PL peaks near 450 and 600 nm, which are attributed to the defect-related emission of ZnS and emission of Mn2? in a ZnS host, respectively. The PLE spectra exhibit near-band-edge absorption of ZnS at 350 nm and the absorption of Mn2? internal-energy levels around 468 nm. The latter absorption is due to the transitions of the 3d5 electronic states of Mn2? from the ground state 6A1 to excited states 4A1 and 4E and plays an important role in improving the absorption of the material in the visible region. ZnS:Mn QDs coated on Zn2SnO4 nanowires show greatly improved sensitization in the visible region as demonstrated by incident photon-to-electron conversion efficiency experiments. Our study also shows that the characteristics of solar-cell performance can be tuned with the Mn concentration.This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-FG02-10ER46728

N-terminal α-amino SUMOylation of cofilin-1 is critical for its regulation of actin depolymerization

Abstract Small ubiquitin-like modifier (SUMO) typically conjugates to target proteins through isopeptide linkage to the ε-amino group of lysine residues. This posttranslational modification (PTM) plays pivotal roles in modulating protein function. Cofilins are key regulators of actin cytoskeleton dynamics and are well-known to undergo several different PTMs. Here, we show that cofilin-1 is conjugated by SUMO1 both in vitro and in vivo. Using mass spectrometry and biochemical and genetic approaches, we identify the N-terminal α-amino group as the SUMO-conjugation site of cofilin-1. Common to conventional SUMOylation is that the N-α-SUMOylation of cofilin-1 is also mediated by SUMO activating (E1), conjugating (E2), and ligating (E3) enzymes and reversed by the SUMO deconjugating enzyme, SENP1. Specific to the N-α-SUMOylation is the physical association of the E1 enzyme to the substrate, cofilin-1. Using F-actin co-sedimentation and actin depolymerization assays in vitro and fluorescence staining of actin filaments in cells, we show that the N-α-SUMOylation promotes cofilin-1 binding to F-actin and cofilin-induced actin depolymerization. This covalent conjugation by SUMO at the N-α amino group of cofilin-1, rather than at an internal lysine(s), serves as an essential PTM to tune cofilin-1 function during regulation of actin dynamics