Author Correction: H2A.Z facilitates licensing and activation of early replication origins.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

H2A.Z facilitates licensing and activation of early replication origins.

DNA replication is a tightly regulated process that ensures the precise duplication of the genome during the cell cycle1. In eukaryotes, the licensing and activation of replication origins are regulated by both DNA sequence and chromatin features2. However, the chromatin-based regulatory mechanisms remain largely uncharacterized. Here we show that, in HeLa cells, nucleosomes containing the histone variant H2A.Z are enriched with histone H4 that is dimethylated on its lysine 20 residue (H4K20me2) and with bound origin-recognition complex (ORC). In vitro studies show that H2A.Z-containing nucleosomes bind directly to the histone lysine methyltransferase enzyme SUV420H1, promoting H4K20me2 deposition, which is in turn required for ORC1 binding. Genome-wide studies show that signals from H4K20me2, ORC1 and nascent DNA strands co-localize with H2A.Z, and that depletion of H2A.Z results in decreased H4K20me2, ORC1 and nascent-strand signals throughout the genome. H2A.Z-regulated replication origins have a higher firing efficiency and early replication timing compared with other origins. Our results suggest that the histone variant H2A.Z epigenetically regulates the licensing and activation of early replication origins and maintains replication timing through the SUV420H1-H4K20me2-ORC1 axis.

A Living Eukaryotic Autocementation Kit from Surface Display of Silica Binding Peptides on Yarrowia lipolytica.

With the development of civil engineering, the demand for suitable cementation materials is increasing rapidly. However, traditional cementation methods are not eco-friendly enough and more sustainable approach such as biobased cementation is required. To meet such demand, Euk.cement, a living eukaryotic cell-based biological autocementation kit, was created in this work. Through the surface display of different silica binding peptides on the fungus Yarrowia lipolytica, Euk.cement cells can immobilize onto any particles with a silica containing surface with variable binding intensity. Meanwhile, recombinant MCFP3 released from the cells will slowly consolidate this binding of cells to particles. The metabolism of immobilized living cells will finally complete the carbonate sedimentation and tightly stick the particles together. The system is designed to be initiated by blue light, making it controllable. This autocementation kit can be utilized for industrial and environmental applications that fit our concerns on making the cementation process eco-friendly.

[Effects of soybean trypsinase inhibitor and defense signaling compounds on detoxification enzymes in Spodoptera litura (F.) larvae].

In a long history of interactions between insects and plants, plants have developed various anti-insect compounds and defense signaling transduction pathways to defend against herbivorous insects, while insects have responded with sophisticated detoxification enzyme systems to protect against the toxicity of anti-insect compounds. In this study, the 2nd or 3rd instar of Spodoptera litura larvae were successively fed with the diets containing 0.5% soybean trypsinase inhibitor (SBTI) for six generations to evaluate the effects of SBTI and defense signaling compounds on the activities of detoxification enzymes carboxylesterase (CarE) and glutathione-S-transferase (GST) in the midgut and fatbody of the larvae. After fed with the diets, the CarE and GST activities in the 5th instar larvae increased significantly. The CarE activity in the midgut and fatbody of the second generation larvae was the highest, being 2.06 and 2.40 times, and 1.96 and 2.70 times of that of the control, and the GST activity in the midgut and fatbody of the fourth and second generations was the highest, being 7.03 and 11.58 times, and 5.71 and 3.60 times of that of the control, respectively. These induced enzyme activities decreased gradually when the larvae continuously grew with the SBTI-containing diets. In addition, when the S. litura larvae were pre-exposed to methyl jasmonate (MeJA) or methyl salicylate (MeSA) for 48 h or fed with the diets containing 0.5% SBTI, the activities of CarE and GST in the midgut and fatbody increased significantly, and, when the 2nd instar larvae were pre-exposed to MeJA and MeSA for 48 h, the effects of SBTI on the GST activity in larval midgut and fatbody were reduced.

[Mechanism of tomato plants enhanced disease resistance against early blight primed by arbuscular mycorrhizal fungus Glomus versiforme].

Arbuscular mycorrhiza (AM) can not only improve host plants nutrient absorption, but also enhance their disease resistance. Taking the tomato (Lycopersicon esculentum) seedlings preinoculated with axbuscular mycorrhizal fungus (AMF) Glomus versiforme as test materials, this paper studied their protective enzyme activities and defense-related genes expression, and their resistance against a fungal pathogen Alternaria solani Sorauer which causes early blight. The seedlings pre-inoculated with AMF and later inoculated with A. solani showed significantly higher activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves. The leaf SOD activity of the dually inoculated plants reached the maximum 18 h after pathogen inoculation, being 28.6%, 79.2% and 82.8% higher than that of the plants with G. versiforme inoculation alone, pathogen inoculation alone, and non-inoculation, and the Leaf POD activity reached the maximum 65 h after pathogen inoculation, being 762%, 18.3%, and 1710% higher, respectively. Real time RT-PCR analysis showed that dual inoculation with C. versiforme and A. solani strongly induced the expression of three defense-related genes. The transcript levels of pathogen-related protein (PR1), basic type beta-1,3-glucanase (PR-2), and chitinase (PR-3) in leaves were 9.67-, 8.54-, and 13.4-fold higher, as compared with the non-inoculation control, respectively. Bioassay showed that the disease incidence and disease index of the seedlings pre-inoculated with C. versiforme were reduced by 36.3% and 61.4%, respectively, as compared with the non-mycorrhizal control plants. These findings indicated that mycorrhizal colonization could induce stronger and quicker defense responses of host tomato plants, and priming could be an important mechanism of the enhanced disease resistance of mycorrhizal tomato plants.