High Hydrophilic and Antibacterial Efficient UV-Curable Silicone-Containing Choline Chloride Quaternary Ammonium Salts Functionalized Materials.

Antibacterial materials with high hydrophobicity have drawbacks such as protein adsorption, bacterial contamination, and biofilm formation, which are responsible for some serious adverse health events. Therefore, antibacterial materials with high hydrophilicity are highly desired. In this paper, UV-curable antibacterial materials are prepared from silicone-containing Choline chloride (ChCl) functionalized hyperbranched quaternary ammonium salts (QAS) and tri-hydroxylethyl acrylate phosphate (TAEP). The materials show high hydrophilic performance because their water contact angle is as low as 19.3°. The materials also exhibit quite high antibacterial efficiency against S. aureus over 95.6%, fairly high transmittance over 90%, and good mechanical performance with tensile strength as high as 6.5 MPa. It reveals that it is a feasible strategy to develop antibacterial materials with low hydrophobicity from silicone-modified ChCl-functionalized hyperbranched QAS.

Effect of transverse colostomy versus ileostomy in colorectal anastomosis on post-operative wound complications: A meta-analysis.

A meta-analysis was conducted to evaluate the effect of colostomy or ileostomy on post-operative wound complications. The research was tested using Embase, PubMed and Cochrane Library databases. Included were randomized, controlled clinical trials (RCTs). A sensitivity analysis and a meta-analysis were carried out. The results indicated that there were no statistically significant differences in the reduction of wound infection between LC and LI. Out of 268 related studies, 5 publications were chosen and examined for compliance. Literature quality was evaluated throughout the trial. Studies with poor literature were excluded. The data were analysed with RevMan 5.3, and a decision was taken to analyse the data with either a stochastic or a fixed-effects model. There were no significant differences in the incidence of post-operative infection in patients with LC (OR, 0.79; 95% CI, 0.34, 1.81; p = 0.57), and the incidence of post-operative anastomotic fistulae (OR, 0.98; 95% CI, 0.30, 3.15; p = 0.97) was not significantly different from that with LI. These meta-analyses indicate that no significant reduction in the incidence of post-operative infections or anastomotic fistulae was observed by either LC or LI.

Imaging of Chloroplast Movement Responses to Light Stimulation in Different Intensities in Rice.

Chloroplast movement has been observed and analyzed since the 19th century. Subsequently, the phenomenon is widely observed in various plant species such as fern, moss, Marchantia polymorpha, and Arabidopsis. However, chloroplast movement in rice is less investigated, presumably due to the thick wax layer on its leaf surface, which reduces light sensitivity to the point that it was previously believed that there was no light-induced movement in rice. In this study, we present a convenient protocol suitable for observing chloroplast movement in rice only by optical microscopy without using special equipment. It will allow researchers to explore other signaling components involved in chloroplast movement in rice.

Formin protein DRT1 affects gross morphology and chloroplast relocation in rice.

Plant height and tiller number are two major factors determining plant architecture and yield. However, in rice (Oryza sativa), the regulatory mechanism of plant architecture remains to be elucidated. Here, we reported a recessive rice mutant presenting dwarf and reduced tillering phenotypes (drt1). Map-based cloning revealed that the phenotypes are caused by a single point mutation in DRT1, which encodes the Class I formin protein O. sativa formin homolog 13 (OsFH13), binds with F-actin, and promotes actin polymerization for microfilament organization. DRT1 protein localized on the plasma membrane (PM) and chloroplast (CP) outer envelope. DRT1 interacted with rice phototropin 2 (OsPHOT2), and the interaction was interrupted in drt1. Upon blue light stimulus, PM localized DRT1 and OsPHOT2 were translocated onto the CP membrane. Moreover, deficiency of DRT1 reduced OsPHOT2 internalization and OsPHOT2-mediated CP relocation. Our study suggests that rice formin protein DRT1/OsFH13 is necessary for plant morphology and CP relocation by modulating the actin-associated cytoskeleton network.

Guidance for assessment of the muscle mass phenotypic criterion for the Global Leadership Initiative on Malnutrition (GLIM) diagnosis of malnutrition.

The Global Leadership Initiative on Malnutrition (GLIM) provides consensus criteria for the diagnosis of malnutrition that can be widely applied. The GLIM approach is based on the assessment of three phenotypic (weight loss, low body mass index, and low skeletal muscle mass) and two etiologic (low food intake and presence of disease with systemic inflammation) criteria, with diagnosis confirmed by any combination of one phenotypic and one etiologic criterion fulfilled. Assessment of muscle mass is less commonly performed than other phenotypic malnutrition criteria, and its interpretation may be less straightforward, particularly in settings that lack access to skilled clinical nutrition practitioners and/or to body composition methodologies. In order to promote the widespread assessment of skeletal muscle mass as an integral part of the GLIM diagnosis of malnutrition, the GLIM consortium appointed a working group to provide consensus-based guidance on assessment of skeletal muscle mass. When such methods and skills are available, quantitative assessment of muscle mass should be measured or estimated using dual-energy x-ray absorptiometry, computerized tomography, or bioelectrical impedance analysis. For settings where these resources are not available, then the use of anthropometric measures and physical examination are also endorsed. Validated ethnic- and sex-specific cutoff values for each measurement and tool are recommended when available. Measurement of skeletal muscle function is not advised as surrogate measurement of muscle mass. However, once malnutrition is diagnosed, skeletal muscle function should be investigated as a relevant component of sarcopenia and for complete nutrition assessment of persons with malnutrition.

Comprehensive treatment of pelvic floor muscle training plus biofeedback electrical stimulation for stress urinary incontinence: a clinical study.

OBJECTIVE: To investigate the clinical effect of pelvic floor muscle training (PFMT) plus biofeedback electrical stimulation (BES) on stress urinary incontinence (SUI). METHODS: 110 patients with SUI admitted to our hospital in the Department of Obstetrics and Gynecology from November 2018 to November 2019 were selected and divided into control group (n=55) and study group (n=55). The study group received PFMT plus BES while the control group received PFMT alone. RESULTS: Compared with the control group, the incontinence quality of life (I-QOL) score and the international consultation on incontinence questionnaire-urinary incontinence short form (ICI-Q-SF) score in the study group were significantly better (P<0.05), and the patients had better pelvic floor muscle endurance, strength, and coordination (P<0.05). CONCLUSION: PFMT plus BES could improve the strength, endurance, and coordination of pelvic floor muscles in SUI patients. It can positively influence the improvement of the I-QOL and ICI-Q-SF scores. CLINICAL TRIAL REGISTRATION: The name of the registry: Chinese Registry of Clinical Trials. TRIAL REGISTRATION NUMBER: ChiCTR21000684765. Trial URL: http://www.chictr.org.cn/showproj.aspx?proj=73654424.

The kinesin-13 protein BR HYPERSENSITIVE 1 is a negative brassinosteroid signaling component regulating rice growth and development.

Phytohormones performed critical roles in regulating plant architecture and thus determine grain yield in rice. However, the roles of brassinosteroids (BRs) compared to other phytohormones in shaping rice architecture are less studied. In this study, we report that BR hypersensitive1 (BHS1) plays a negative role in BR signaling and regulate rice architecture. BHS1 encodes the kinesin-13a protein and regulates grain length. We found that bhs1 was hypersensitive to BR, while BHS1-overexpression was less sensitive to BR compare to WT. BHS1 was down-regulated at RNA and protein level upon exogenous BR treatment, and proteasome inhibitor MG132 delayed the BHS1 degradation, indicating that both the transcriptional and posttranscriptional regulation machineries are involved in BHS1-mediated regulation of plant growth and development. Furthermore, we found that the BR-induced degradation of BHS1 was attenuated in Osbri1 and Osbak1 mutants, but not in Osbzr1 and Oslic mutants. Together, these results suggest that BHS1 is a novel component which is involved in negative regulation of the BR signaling downstream player of BRI1.

Identification and characterization of profilin gene family in rice

BACKGROUND Profilin proteins (PRFs) are small (12­15 kD) actin-binding protein, which play a significant role in cytoskeleton dynamics and plant development via regulating actin polymerization. Profilins have been well documented in Arabidopsis, Zea mays L. as well as Phaseolus vulgaris, however no such fully characterization of rice (Oryza sativa L.) profilin gene family has been reported thus far. RESULTS In the present study, a comprehensive genome-wide analysis of rice PRF genes was completed and three members were identified. OsPRF1 and OsPRF2 shared 98.5% similarity (6 nucleotide divergence), but the deduced amino acid sequences of OsPRF1 and OsPRF2 are fully identical. In contrast, the OsPRF3 presents relatively lower similarity with OsPRF1 and OsPRF2. Phylogenetic analysis also support that OsPRF1 has a closer relationship with OsPRF2. Expression pattern analysis revealed the differential expression of OsPRFs in tissues of mature plant, which suggested the potential spatial functional specificity for rice profilin genes. Subcellular localization analysis revealed the OsPRFs were localized in cytoplasm and nucleus and all of them could bind actin monomers. Furthermore, abiotic stresses and hormones treatments assay indicated that the three OsPRF genes could be differentially regulated, suggesting that OsPRF genes might participate in different stress processes in rice. CONCLUSIONS Taken together, our study provides a comprehensive analysis of the OsPRF gene family and will provide a basis for further studies on their roles in rice development and in response to abiotic stresses

iTRAQ-based proteomic analysis provides insights into the molecular mechanisms of rice formyl tetrahydrofolate deformylase in salt response.

MAIN CONCLUSION: A new molecular mechanism of tetrahydrofolate deformylase involved in the salt response presumably affects mitochondrial and chloroplast function by regulating energy metabolism and accumulation of reactive oxygen species. High salinity severely restrains plant growth and development, consequently leading to a reduction in grain yield. It is therefore critical to identify the components involved in plant salt resistance. In our previous study, we identified a rice leaf early-senescence mutant hpa1, which encodes a formyl tetrahydrofolate deformylase (Xiong et al. in Sci China Life Sci 64(5):720-738, 2021). Here, we report that HPA1 also plays a role in the salt response. To explore the molecular mechanism of HPA1 in salt resistance, we attempted to identify the differentially expressed proteins between wild type and hpa1 mutant for salinity treatment using an iTRAQ-based comparative protein quantification approach. A total of 4598 proteins were identified, of which 279 were significantly altered, including 177 up- and 102 down-regulated proteins. A functional analysis suggested that the 279 differentially expressed proteins are involved mainly in the regulation of oxidative phosphorylation, phenylpropanoid biosynthesis, photosynthesis, posttranslational modifications, protein turnover and energy metabolism. Moreover, a deficiency in HPA1 impaired chlorophyll metabolism and photosynthesis in chloroplasts and affected the electron flow of the electron transport chain in mitochondria. These changes led to abnormal energy metabolism and accumulation of reactive oxygen species, which may affect the permeability and integrity of cell membranes, leading to cell death. In addition, the results were verified by transcriptional or physiological experiments. Our results provide an insight into a new molecular mechanism of the tetrahydrofolate cycle protein formyl tetrahydrofolate deformylase, which is involved in the salt response, presumably by affecting mitochondrial and chloroplast function regulating energy metabolism and accumulation of reactive oxygen species under salt stress.

A ß-ketoacyl carrier protein reductase confers heat tolerance via the regulation of fatty acid biosynthesis and stress signaling in rice.

Heat stress is a major environmental threat affecting crop growth and productivity. However, the molecular mechanisms associated with plant responses to heat stress are poorly understood. Here, we identified a heat stress-sensitive mutant, hts1, in rice. HTS1 encodes a thylakoid membrane-localized ß-ketoacyl carrier protein reductase (KAR) involved in de novo fatty acid biosynthesis. Phylogenetic and bioinformatic analysis showed that HTS1 probably originated from streptophyte algae and is evolutionarily conserved in land plants. Thermostable HTS1 is predominantly expressed in green tissues and strongly induced by heat stress, but is less responsive to salinity, cold and drought treatments. An amino acid substitution at A254T in HTS1 causes a significant decrease in KAR enzymatic activity and, consequently, impairs fatty acid synthesis and lipid metabolism in the hts1 mutant, especially under heat stress. Compared to the wild-type, the hts1 mutant exhibited heat-induced higher H2 O2 accumulation, a larger Ca2+ influx to mesophyll cells, and more damage to membranes and chloroplasts. Also, disrupted heat stress signaling in the hts1 mutant depresses the transcriptional activation of HsfA2s and the downstream target genes. We suggest that HTS1 is critical for underpinning membrane stability, chloroplast integrity and stress signaling for heat tolerance in rice.

Formyl tetrahydrofolate deformylase affects hydrogen peroxide accumulation and leaf senescence by regulating the folate status and redox homeostasis in rice.

It is well established that an abnormal tetrahydrofolate (THF) cycle causes the accumulation of hydrogen peroxide (H2O2) and leaf senescence, however, the molecular mechanism underlying this relationship remains largely unknown. Here, we reported a novel rice tetrahydrofolate cycle mutant, which exhibited H2O2 accumulation and early leaf senescence phenotypes. Map-based cloning revealed that HPA1 encodes a tetrahydrofolate deformylase, and its deficiency led to the accumulation of tetrahydrofolate, 5-formyl tetrahydrofolate and 10-formyl tetrahydrofolate, in contrast, a decrease in 5,10-methenyl-tetrahydrofolate. The expression of tetrahydrofolate cycle-associated genes encoding serine hydroxymethyl transferase, glycine decarboxylase and 5-formyl tetrahydrofolate cycloligase was significantly down-regulated. In addition, the accumulation of H2O2 in hpa1 was not caused by elevated glycolate oxidation. Proteomics and enzyme activity analyses further revealed that mitochondria oxidative phosphorylation complex I and complex V were differentially expressed in hpa1, which was consistent with the H2O2 accumulation in hpa1. In a further feeding assay with exogenous glutathione (GSH), a non-enzymatic antioxidant that consumes H2O2, the H2O2 accumulation and leaf senescence phenotypes of hpa1 were obviously compensated. Taken together, our findings suggest that the accumulation of H2O2 in hpa1 may be mediated by an altered folate status and redox homeostasis, subsequently triggering leaf senescence.

[Accuracy of 6D computed-derived implant guides made in China for dental implant surgery in edentulous patients].

PURPOSE: To evaluate the accuracy of 6D computed-derived implant guides made in China, in order to provide methods and basis for reducing deviation. METHODS: 3D rapid prototyping technique was used to fabricate implant guides for auxiliary surgical implantation in edentulous patients, and the position deviation between the preoperative design and the actual implant was measured. Sixteen edentulous patients with 172 implantation sites were measured. In 10 patients, six implants were implanted in the maxilla, 4 implants in the mandible, and 6 implants were implanted both in the maxilla and mandible of 6 patients. A total of 28 implants were tilted implant in 14 patients. Preoperative cone-beam CT(CBCT) data were imported into the 6D Dental Planning Software to design and make the implant guides. Digital guides were used to assist implant placement. Preoperative design and postoperative CBCT were imported into the software for 3D reconstruction and registration, and then exported to Geomagic Studio software for analysis to obtain the deviation between the preoperative design and the implantation, so as to analyze the accuracy of the guides. The differences were analyzed by SPSS 25.0 software package with paired t-test and single factor analysis of variance. RESULTS: The distance deviation of implant neck center point was (0.83±0.27) mm and the horizontal deviation was (0.60±0.21) mm. The distance deviation of implant bottom center point was (1.11±0.35) mm, and the vertical deviation was (0.45±0.19) mm. The angle deviation was (3.16±1.73)°. CONCLUSIONS: The 6D computed-derived implant guides made in China can improve the accuracy and efficiency of implant surgery for edentulous patients and obtain a better long-term clinical effect to meet clinical requirements well. Since the deviation is similar to other implant guide plate systems that reported aborad, it must be taken into account in the process of clinical design, in order to avoid risks and unnecessary complications. This method is worthy of wide clinical application.

New Geographical Insights of the Latest Expansion of Fusarium oxysporum f.sp. cubense Tropical Race 4 Into the Greater Mekong Subregion.

Banana is the most popular and most exported fruit and also a major food crop for millions of people around the world. Despite its importance and the presence of serious disease threats, research into this crop is limited. One of those is Panama disease or Fusarium wilt. In the previous century Fusarium wilt wiped out the "Gros Michel" based banana industry in Central America. The epidemic was eventually quenched by planting "Cavendish" bananas. However, 50 years ago the disease recurred, but now on "Cavendish" bananas. Since then the disease has spread across South-East Asia, to the Middle-East and the Indian subcontinent and leaped into Africa. Here, we report the presence of Fusarium oxysporum f.sp. cubense Tropical Race 4 (Foc TR4) in "Cavendish" plantations in Laos, Myanmar, and Vietnam. A combination of classical morphology, DNA sequencing, and phenotyping assays revealed a very close relationship between the Foc TR4 strains in the entire Greater Mekong Subregion (GMS), which is increasingly prone to intensive banana production. Analyses of single-nucleotide polymorphisms enabled us to initiate a phylogeography of Foc TR4 across three geographical areas-GMS, Indian subcontinent, and the Middle East revealing three distinct Foc TR4 sub-lineages. Collectively, our data place these new incursions in a broader agroecological context and underscore the need for awareness campaigns and the implementation of validated quarantine measures to prevent further international dissemination of Foc TR4.

UMP kinase activity is involved in proper chloroplast development in rice.

Isolation of leaf-color mutants is important in understanding the mechanisms of chloroplast biogenesis and development. In this study, we identified and characterized a rice (Oryza sativa) mutant, yellow leaf 2 (yl2), exhibiting pale yellow leaves with a few longitudinal white stripes at the early seedling stage then gradually turning yellow. Genetic analyses revealed that YL2 encodes a thylakoid membrane-localized protein with significant sequence similarity to UMP kinase proteins in prokaryotes and eukaryotes. Prokaryotic UMP kinase activity was subsequently confirmed, with YL2 deficiency causing a significant reduction in chlorophyll accumulation and photochemical efficiency. Moreover, YL2 is also light dependent and preferentially expressed in green tissues. Chloroplast development was abnormal in the yl2 mutant, possibly due to reduced accumulation of thylakoid membranes and a lack of normal stroma lamellae. 2D Blue-Native SDS-PAGE and immunoblot analyses revealed a reduction in several subunits of photosynthetic complexes, in particular, the AtpB subunit of ATP synthase, while mRNA levels of corresponding genes were unchanged or increased compared with the wild type. In addition, we observed a significant decrease (ca. 36.3%) in cpATPase activity in the yl2 mutant compared with the wild type. Taken together, our results suggest that UMP kinase activity plays an essential role in chloroplast development and regulating cpATPase biogenesis in rice.

Noble-metal-free ternary CN-ZCS-NiS nanocomposites for enhanced solar photocatalytic H2-production activity.

Photocatalytic hydrogen production from water using a noble-metal-free catalyst has aroused tremendous and interdisciplinary attention. In this work, we report a series of original noble-metal-free ternary nanocomposites of C3N4-Zn0.5Cd0.5S heterojunctions loaded with NiS by a precipitation hydrothermal method. They were characterized by XRD, TEM, SEM-EDS, UV-vis, XPS, PL spectra, and transient photocurrent response measurements. The facts proved that they were efficient and stable photocatalysts to enhance the hydrogen production activity prepared by the precipitation hydrothermal method. Among these photocatalysts, C3N4-Zn0.5Cd0.5S-1% NiS showed excellent photocatalytic performance with a H2-production rate of 53.190 mmol g-1 h-1 which is 405 times higher than the pure CN. The high catalytic activity was attributed to the synergistic effect of the NiS cocatalyst and the nanoheterojunctions between ZCS nanoparticles and 2D CN nanosheets, which were propitious to accelerate charge transfer, promote the separation of photogenerated electron-hole pairs and expedite the surface H2-evolution kinetics.

[Clinical study of titanium mesh in conjunction with concentrate growth factors to rebuild severe bone defect of anterior maxilla].

PURPOSE: To evaluate the effect of overlaying titanium mesh with concentrate growth factors(CGF) for rebuilding severe buccal bone defect of anterior maxilla when used in association with dental implantation. METHODS: Twenty patients with severe buccal bone defect of maxilla were selected. A total of 25 dental implants were placed, including 5 cases in bilateral central incisor area and 15 cases in unilateral central incisor area. After implantation, the defects were treated with Bio-oss and Bio-guid in conjunction with fixation of titanium mesh and then CGF technology was used. Two-stage surgery was carried out after 6 months of submerged healing, and permanent prosthesis was used 3 months after temporary restoration. The repairs of the defect were observed at the second stage surgery. The height of margin bone around implants and the thickness of bone at implants lingual side were measured, at the time of the second stage operation, and 3, 6, 12, 18 months after permanent restoration. The differences were analyzed by SPSS 19.0 software package with multi-sample nonparametric test and Fierdman test. RESULTS: At the time of second operation, the bone plate at lingual side was completely reconstructed, and new bone was formed at the top of implants. Clinical measurements showed that the averaged thickness of bone at lingual side was (2.69±0.154) mm at that time. Three, 6, 12, 18 months after restoration, the values were (2.67±0.152) mm, (2.66±0.153) mm, (2.65±0.153) mm, (2.65±0.151) mm, respectively. Implant-abutment junction was used as a base line to assess vertical bone absorption, the marginal bone of implant neck at lingual side was all inferior to the base line, the distance was (0.02±0.048) mm, (0.69±0.085) mm，(0.87±0.019) mm, (0.87±0.013) mm, respectively. Statistical analysis showed the thickness of bone of labial side decreased significantly over time after permanent restoration (P<0.01). Likewise, the height of marginal bone was also decreased significantly (P<0.01). However, the difference between them at 12 months and 18 months was not statistically significant (P>0.05). CONCLUSIONS: The results indicate that bone augmentation at maxilla can be achieved using titanium mesh in conjunction with CGF. The height and thickness of newly formed bone at the implant neck margin will be stabilized after 1 year. This method is worthy of wide clinical application.

A Nucleus-Encoded Chloroplast Protein YL1 Is Involved in Chloroplast Development and Efficient Biogenesis of Chloroplast ATP Synthase in Rice.

Chloroplast ATP synthase (cpATPase) is an importance thylakoid membrane-associated photosynthetic complex involved in the light-dependent reactions of photosynthesis. In this study, we isolated and characterized a rice (Oryza sativa) mutant yellow leaf 1 (yl1), which exhibits chlorotic leaves throughout developmental stages. The YL1 mutation showed reduced chlorophyll contents, abnormal chloroplast morphology, and decreased photochemical efficiency. Moreover, YL1 deficiency disrupts the expression of genes associated with chloroplast development and photosynthesis. Molecular and genetic analyses revealed that YL1 is a nucleus-encoded protein with a predicted transmembrane domain in its carboxyl-terminus that is conserved in the higher plant kingdom. YL1 localizes to chloroplasts and is preferentially expressed in green tissues containing chloroplasts. Immunoblot analyses showed that inactivation of YL1 leads to drastically reduced accumulation of AtpA (α) and AtpB (ß), two core subunits of CF1αß subcomplex of cpATPase, meanwhile, a severe decrease (ca. 41.7%) in cpATPase activity was observed in the yl1-1 mutant compared with the wild type. Furthermore, yeast two-hybrid and bimolecular fluorescence complementation assays revealed a specific interaction between YL1 and AtpB subunit of cpATPase. Taken together, our results suggest that YL1 is a plant lineage-specific auxiliary factor involved in the biogenesis of the cpATPase complex, possibly via interacting with the ß-subunit.

Degradation of MONOCULM 1 by APC/C(TAD1) regulates rice tillering.

A rice tiller is a specialized grain-bearing branch that contributes greatly to grain yield. The MONOCULM 1 (MOC1) gene is the first identified key regulator controlling rice tiller number; however, the underlying mechanism remains to be elucidated. Here we report a novel rice gene, Tillering and Dwarf 1 (TAD1), which encodes a co-activator of the anaphase-promoting complex (APC/C), a multi-subunit E3 ligase. Although the elucidation of co-activators and individual subunits of plant APC/C involved in regulating plant development have emerged recently, the understanding of whether and how this large cell-cycle machinery controls plant development is still very limited. Our study demonstrates that TAD1 interacts with MOC1, forms a complex with OsAPC10 and functions as a co-activator of APC/C to target MOC1 for degradation in a cell-cycle-dependent manner. Our findings uncovered a new mechanism underlying shoot branching and shed light on the understanding of how the cell-cycle machinery regulates plant architecture.

Genome-wide mapping of Arabidopsis thaliana origins of DNA replication and their associated epigenetic marks.

Genome integrity requires faithful chromosome duplication. Origins of replication, the genomic sites at which DNA replication initiates, are scattered throughout the genome. Their mapping at a genomic scale in multicellular organisms has been challenging. In this study we profiled origins in Arabidopsis thaliana by high-throughput sequencing of newly synthesized DNA and identified ~1,500 putative origins genome-wide. This was supported by chromatin immunoprecipitation and microarray (ChIP-chip) experiments to identify ORC1- and CDC6-binding sites. We validated origin activity independently by measuring the abundance of nascent DNA strands. The midpoints of most A. thaliana origin regions are preferentially located within the 5' half of genes, enriched in G+C, histone H2A.Z, H3K4me2, H3K4me3 and H4K5ac, and depleted in H3K4me1 and H3K9me2. Our data help clarify the epigenetic specification of DNA replication origins in A. thaliana and have implications for other eukaryotes.

SET DOMAIN GROUP2 is the major histone H3 lysine [corrected] 4 trimethyltransferase in Arabidopsis.

Posttranslational modifications of histones play important roles in modulating chromatin structure and regulating gene expression. We have previously shown that more than two thirds of Arabidopsis genes contain histone H3 methylation at lysine 4 (H3K4me) and that trimethylation of H3K4 (H3K4me3) is preferentially located at actively transcribed genes. In addition, several Arabidopsis mutants with locus-specific loss of H3K4me have been found to display various developmental abnormalities. These findings suggest that H3K4me3 may play important roles in maintaining the normal expression of a large number of genes. However, the major enzyme(s) responsible for H3K4me3 has yet to be identified in plants, making it difficult to address questions regarding the mechanisms and functions of H3K4me3. Here we described the characterization of SET DOMAIN GROUP 2 (SDG2), a large Arabidopsis protein containing a histone lysine methyltransferase domain. We found that SDG2 homologs are highly conserved in plants and that the Arabidopsis SDG2 gene is broadly expressed during development. In addition, the loss of SDG2 leads to severe and pleiotropic phenotypes, as well as the misregulation of a large number of genes. Consistent with our finding that SDG2 is a robust and specific H3K4 methyltransferase in vitro, the loss of SDG2 leads to a drastic decrease in H3K4me3 in vivo. Taken together, these results suggest that SDG2 is the major enzyme responsible for H3K4me3 in Arabidopsis and that SDG2-dependent H3K4m3 is critical for regulating gene expression and plant development.