Transient expression of a TaGRF4-TaGIF1 complex stimulates wheat regeneration and improves genome editing

Science China Life Sciences - Genome editing is an unprecedented technological breakthrough but low plant regeneration frequencies and genotype dependence hinder its implementation for crop...     

Shortening the sgRNA-DNA interface enables SpCas9 and eSpCas9(1.1) to nick the target DNA strand

The length of the sgRNA-DNA complementary sequence is a key factor influencing the cleavage activity of Streptococcus pyogenes Cas9 (SpCas9) and its variants. The detailed mechanism remains unknown. Here, based on in vitro cleavage assays and base editing analysis, we demonstrate that reducing the length of this complementary region can confer nickase activity on SpCas9 and eSpCas9(1.1). We also show that these nicks are made on the target DNA strand. These properties encouraged us to develop a dual-functional system that simultaneously carries out double-strand DNA cleavage and C-to-T base conversions at separate targets. This system provides a novel tool for achieving trait stacking in plants.

     

New insights into intracellular lipid binding proteins: The role of buried water

The crystal structures of most intracellular lipid binding proteins (LBPs) show between 5 and 20 internally bound water molecules, depending on the presence or the absence of ligand inside the protein cavity. The structural and functional significance of these waters has been discussed for several LBPs based on studies that used various biophysical techniques. The present work focuses on two very different LBPs, heart-type fatty acid binding protein (H-FABP) and ileal lipid binding protein (ILBP). Using high-resolution nuclear magnetic resonance spectroscopy, certain resonances belonging to side-chain protons that are located inside the water-filled lipid binding cavity were observed. In the case of H-FABP, the pH- and temperature-dependent behavior of selected side-chain resonances (Ser82 OgH and the imidazole ring protons of His93) indicated an unusually slow exchange with the solvent, implying that the intricate hydrogen-bonding network of amino-acid side-chains and water molecules in the protein interior is very rigid. In addition, holo H-FABP appeared to display a reversible self-aggregation at physiological pH. For ILBP, on the other hand, a more solvent-accessible protein cavity was deduced based on the pH titration behavior of its histidine residues. Comparison with data from other LBPs implies that the evolutionary specialization of LBPs for certain ligand types was not only because of mutations of residues directly involved in ligand binding but also to a refinement of the internal water scaffold.     

天目山国家级自然保护区旅游公路对节肢动物群落的影响及其动物致死特征

2016年8月和2017年8月, 在天目山国家级自然保护区采用样线法和样方法调查了旅游公路的运营对节肢动物群落的影响及道路致死状况。结果表明, 公路两侧昆虫的遇见率(14.55±4.45 只•km–1)显著的高于林中(8.27±2.22 只•km–1; P=0.018), 公路两侧0—5 m区域内节肢动物的捕获数(33.45±3.23 只•m–2)也显著的高于20—30 m区域(23.92±4.72只•m–2; P=0.027); 并且距离公路0—5 m区域内的节肢动物群落Shannon-Wiener多样性指数(2.21)也高于20—30 m区域(1.90), 说明公路运营对节肢动物群落产生正的边缘效应。动物的平均道路致死率为9.01±3.17只•km–1, 其中昆虫的道路致死数量最高, 占总数的69.44%。说明道路边缘可能由于车辆的行驶而变成生态陷阱。另外还记录到大量的脊椎动物被车辆撞死, 造成动物非自然死亡, 进而对当地的野生动物群落产生明显的负面效应。     

CRISPR/Cas9-introduced single and multiple mutagenesis in strawberry

正CRISPR/Cas9-mediated genome editing is a powerful tool for life science research. Recently, strawberry (Fragaria × ananassa), an important horticultural crop, has emerged as a model organism for investigating the regulatory mechanisms of fruit development and ripening (Shulaev et al., 2011; Jia et al., 2013, 2017; Kang et al., 2013; Han et al., 2015). While most cultivated strawberries