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Summary: Ribosome biogenesis is a highly dynamic and orchestrated process facilitated by hundreds of ribosomal biogenesis factors and small nucleolar RNAs. While many of the advances are derived from studies in yeast, ribosome biogenesis remains largely unknown in plants despite its importance to plant growth and development.Through characterizing the maize (Zea mays) defective kernel and embryo‐lethal mutant dek58, we show that DEK58 encodes an Rrp15p domain‐containing protein with 15.3% identity to yeast Rrp15. Over‐expression of DEK58 rescues the mutant phenotype.DEK58 is localized in the nucleolus. Ribosome profiling and RNA gel blot analyses show that the absence of DEK58 reduces ribosome assembly and impedes pre‐rRNA processing, accompanied by the accumulation of nearly all the pre‐rRNA processing intermediates and the production of an aberrant processing product P‐25S*. DEK58 interacts with ZmSSF1, a maize homolog of the yeast Ssf1 in the 60S processome. DEK58 and ZmSSF1 interact with ZmCK2α, a putative component of the yeast UTP‐C complex involved in the small ribosomal subunit processome.These results demonstrate that DEK58 is essential to seed development in maize. It functions in the early stage of pre‐rRNA processing in ribosome biogenesis, possibly through interacting with ZmSSF1 and ZmCK2α in maize. [ABSTRACT FROM AUTHOR]

The kernel serves as the storage organ and harvestable component of maize, and it plays a crucial role in determining crop yield and quality. Understanding the molecular and genetic mechanisms of kernel development is of considerable importance for maize production. In this study, we obtained a mutant, which we designated defective kernel 407 (dek407), through ethyl methanesulfonate mutagenesis. The dek407 mutant exhibited reduced kernel size and kernel weight, as well as delayed grain filling compared with those of the wild type. Positional cloning and an allelism test revealed that Dek407 encodes a nitrate transporter 1/peptide transporter family (NPF) protein and is the allele of miniature 2 (mn2) that was responsible for a poorly filled defective kernel phenotype. A transcriptome analysis of the developing kernels showed that the mutation of Dek407 altered the expression of phytohormone-related genes, especially those genes associated with indole-3-acetic acid synthesis and signaling. Phytohormone measurements and analysis indicated that the endogenous indole-3-acetic acid content was significantly reduced by 66% in the dek407 kernels, which may be the primary cause of the defective phenotype. We further demonstrated that natural variation in Dek407 is associated with kernel weight and kernel size. Therefore, Dek407 is a potential target gene for improvement of maize yield. [ABSTRACT FROM AUTHOR]

Purpose: Delineation of the clinical target volume (CTV) and organs‐at‐risk (OARs) is important in cervical cancer radiotherapy. But it is generally labor‐intensive, time‐consuming, and subjective. This paper proposes a parallel‐path attention fusion network (PPAF‐net) to overcome these disadvantages in the delineation task. Methods: The PPAF‐net utilizes both the texture and structure information of CTV and OARs by employing a U‐Net network to capture the high‐level texture information, and an up‐sampling and down‐sampling (USDS) network to capture the low‐level structure information to accentuate the boundaries of CTV and OARs. Multi‐level features extracted from both networks are then fused together through an attention module to generate the delineation result. Results: The dataset contains 276 computed tomography (CT) scans of patients with cervical cancer of staging IB‐IIA. The images are provided by the West China Hospital of Sichuan University. Simulation results demonstrate that PPAF‐net performs favorably on the delineation of the CTV and OARs (e.g., rectum, bladder and etc.) and achieves the state‐of‐the‐art delineation accuracy, respectively, for the CTV and OARs. In terms of the Dice Similarity Coefficient (DSC) and the Hausdorff Distance (HD), 88.61% and 2.25 cm for the CTV, 92.27% and 0.73 cm for the rectum, 96.74% and 0.68 cm for the bladder, 96.38% and 0.65 cm for the left kidney, 96.79% and 0.63 cm for the right kidney, 93.42% and 0.52 cm for the left femoral head, 93.69% and 0.51 cm for the right femoral head, 87.53% and 1.07 cm for the small intestine, and 91.50% and 0.84 cm for the spinal cord. Conclusions: The proposed automatic delineation network PPAF‐net performs well on CTV and OARs segmentation tasks, which has great potential for reducing the burden of radiation oncologists and increasing the accuracy of delineation. In future, radiation oncologists from the West China Hospital of Sichuan University will further evaluate the results of network delineation, making this method helpful in clinical practice. [ABSTRACT FROM AUTHOR]

A simple and feasible method to enhance the wear resistance of ultra‐high molecular weight polyethylene (UHMWPE) fibers was reported. The graphite oxide (GO) prepared using improved Hummer's method was surface modified with hexadecylamine to improve its compatibility with UHMWPE. Combined with well‐dispersion of modified‐GO (m‐GO) in dichloromethane and the fact that the viscosity of UHMWPE suspension can be decreased by dichloromethane, the well dispersed m‐GO/dichloromethane was added into UHMWPE suspension to improve m‐GO dispersion in UHMWPE fibers. Finally, UHMWPE fibers with different m‐GO concentration were prepared using gel spinning technology. The effect of m‐GO concentration on the structure and properties of modified UHMWPE fibers were investigated. The results indicated that the melting temperature and crystallinity of m‐GO modified UHMWPE fibers increased with increasing of m‐GO concentration, while the fiber's crystal sizes and orientation increased, thus the tensile strength of m‐GO modified UHMWPE fibers remained almost undamaged. The introduction of m‐GO is beneficial to the formation of smooth transfer film on fiber's surface, which enhanced the self‐lubrication of UHMWPE fibers. Compared with pure UHMWPE fiber, the UHMWPE fiber containing 1.5 wt% m‐GO had enhanced wear resistance by 55.4% and still maintained high tensile strength of 29.98 cN dtex−1. [ABSTRACT FROM AUTHOR]

Interface variation in the extraction and drying process of ultra‐high molecular weight polyethylene (UHMWPE) gel fiber results in different shrinkage at different direction. The essence of shrinkage lies in the crystallization of UHMWPE chains under the effect of interface tension. However, UHMWPE gel fiber prepared with different solution concentration has different chain entanglement points density that can hinder the regular stacking for UHMWPE chains. The restriction for axis shrinkage of UHMWPE gel fiber facilitates the orientation of UHMWPE chains that is beneficial to improve the tensile strength of UHMWPE drawn fiber. Combined with multiple methods of Wide angle X‐ray diffraction, Small‐angle X‐ray scattering, Differential scanning calorimetry and sonic orientation, the structural evolution of UHMWPE fiber with different shrinkage ratio and different concentration was investigated. Meanwhile, the suitability for UHMWPE fibers in production was evaluated by final tensile strength of the fibers. Here, a structural evolution model is proposed to elucidate the correlation between the shrinkage and the structure and properties of UHMWPE fibers prepared with different solution concentration. [ABSTRACT FROM AUTHOR]

Ribosome biogenesis is a fundamental process in all eukaryotic cells and is coupled with the processing and maturation of pre-rRNAs. Maize is a primary staple crop across the world, but little is known about the exact pre-rRNA processing sites and pathways in this species. In this study, we present a detailed model of the pathway by identifying the critical endonucleolytic cleavage sites and determining the pre-rRNA intermediates by circular reverse-transcription PCR and northern blot analysis. We demonstrate that two pathways coexist in maize to promote the processing of 35S pre-rRNA, and that the processing of 27SA pre-rRNA can proceed via two different pathways, which are distinguished based on the order of ITS1 removal and ITS2 cleavage. Compared with yeast and mammals, this new 27SA pre-rRNA processing mechanism is unique to maize and other higher plants. In addition, we demonstrate that maize can modulate pre-rRNA processing levels in response to chilling and heat stress, as indicated by a significant reduction of the P-A3 intermediate. Our study provides information that will facilitate future research on ribosome biogenesis and pre-rRNA processing in maize. [ABSTRACT FROM AUTHOR]

Lodging under nitrogen (N)-luxury conditions substantially reduces crop yield and seed quality. However, the molecular mechanisms of plant lodging resistance remain largely unclear, especially in maize. We report here that the expression of ZmmiR528, a monocot-specific microRNA, is induced by N luxury but reduced by N deficiency. We show by the thioacidolysis and acetyl bromide analysis that N luxury significantly reduces the generation of H, G, and S monomers of the lignin as well as its total content in maize shoots. We further demonstrate that ZmLACCASE3 ( ZmLAC3 ) and ZmLACCASE5 ( ZmLAC5 ), which encode the copper-containing laccases, are the targets of ZmmiR528. In situ hybridization showed that ZmmiR528 is mainly expressed in maize vascular tissues. Knockdown of ZmmiR528 or overexpression of ZmLAC3 significantly increased the lignin content and rind penetrometer resistance of maize stems. In contrast, transgenic maize plants overexpressing ZmmiR528 had reduced lignin content and rind penetrometer resistance and were prone to lodging under N-luxury conditions. RNA-sequencing analysis revealed that ZmPAL7 and ZmPAL8 are upregulated in transgenic maize lines downregulating ZmmiR528 . Under N-luxury conditions, the expression levels of ZmPAL s were much higher in ZmmiR528-knockdown lines than in the wild type and transgenic maize lines overexpressing ZmmiR528. Taken together, these results indicate that, by regulating the expression of ZmLAC3 and ZmLAC5 , ZmmiR528 affects maize lodging resistance under N-luxury conditions. [ABSTRACT FROM AUTHOR]

Summary: Ribosome biogenesis is a fundamental process in eukaryotic cells. Although Urb2 protein has been implicated in ribosome biogenesis in yeast, the Urb2 domain is loosely conserved between plants and yeast, and the function of Urb2 protein in plants remains unknown. Here, we isolated a maize mutant, designated as urb2, with defects in kernel development and vegetative growth. Positional cloning and transgenic analysis revealed that urb2 encodes an Urb2 domain‐containing protein. Compared with the wild‐type (WT), the urb2 mutant showed decreased ratios of 60S/40S and 80S/40S and increased ratios of polyribosomes. The pre‐rRNA intermediates of 35/33S rRNA, P‐A3 and 18S‐A3 were significantly accumulated in the urb2 mutant. Transcriptome profiling of the urb2 mutant indicated that ZmUrb2 affects the expression of a number of ribosome‐related genes. We further demonstrated that natural variations in ZmUrb2 are significantly associated with maize kernel length. The overall results indicate that, by affecting pre‐rRNA processing, the Urb2 protein is required for ribosome biogenesis in maize. [ABSTRACT FROM AUTHOR]

The biocompatible, quickly recoverable, mechanically strong and tough polymer hydrogels have great potential for biomedical applications. A novel carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/polyacrylamide (PAM) nanocomposite (NC) hydrogel with excellent mechanical performance was synthesized through a facile, one-pot free radical polymerization, using GO nanosheets as the crosslink centers instead of toxic organic molecules. The content of GO nanosheets and CMCTs has great influence on the mechanical properties of CMCTs/GO/PAM NC hydrogels. When the amount of GO nanosheets is 0.118 wt % and CMCTs is 1.5 wt % (to the total weight of CMCTs and acrylamide), CMCTs/GO/PAM hydrogel displays a compressive stress as high as 5.8 MPa at the breaking deformation of 87.5% and a tensile strength of 223.6 kPa at the failure strain of 631%. Besides, with nearly complete recovery in 1 min at the room temperature after unloading, the CMCTs/GO/PAM hydrogels exhibit excellent fast recoverability. Additionally, the CMCTs/GO/PAM hydrogels also have an obvious pH-responsive property. [ABSTRACT FROM AUTHOR]

Heterosis has widely been used to increase grain yield and quality. In this study, the genetic basis of heterosis on grain yield and its main components in maize were examined over 2 years in two locations in two test populations constructed from a set of 184 chromosome segment substitution lines (CSSLs) and two inbred lines (Zheng58 and Xun9058). Of the 169 heterotic loci (HL) associated with grain yield and its five components identified in CSSL × Zheng58 and CSSL × Xun9058 test populations, only 25 HL were detected in both populations. The comparison of quantitative trait loci (QTLs) detected in the CSSL population with HL detected in the two test populations revealed that only 15.46% and 17.35% of the HL in the given populations respectively, shared the same chromosomal regions as that of the corresponding QTLs and showed dominant effects as well as pleiotropism with additive and dominant effects. In addition, most of the HL (74.23% and 74.49%) had overdominant effects. These results suggest that overdominance is the main contributor to the effects of heterosis on grain yield and its components in maize, and different HL are associated with heterosis for different traits in different hybrids. [ABSTRACT FROM AUTHOR]