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Limited natural genetic diversity restricts the creation of excellent crops. Modeling-guided rational design represents a promising protein engineering technology to optimize existing genes for desired agronomic traits. Rational design coupled with other engineering approaches could also be applied in artificial gene improvement for the creation of economically valuable crops.

Flowering is a critical stage in plant life history, which is coordinated by environmental signals and endogenous cues. Phytomelatonin is a widely distributed indoleamine present in all living organisms and plays pleiotropic roles in plant growth and development. Recent evidence has established that phytomelatonin could modulate flowering in many species, probably in a concentration-dependent manner. Phytomelatonin seems to associate with floral meristem identification and floral organ formation, and the fluctuation of phytomelatonin might be important for flowering. Regarding the underlying mechanisms, phytomelatonin interacts with the central components of floral gene regulatory networks directly or indirectly, including the MADS-box gene family, phytohormones, and reactive oxygen species (ROS). From an evolutionary point of view, the actions of phytomelatonin in flowering probably evolved during the period of the diversification of flowering plants and could be regarded as a functional extension of its primary activities. The presumed evolutionary history of phytomelatonin-modulated flowering is proposed, presented in the chronological order of the appearance of phytomelatonin and core flowering regulators, namely DELLA proteins, ROS, and phytohormones. Further efforts are needed to address some intriguing aspects, such as the exploration of the association between phytomelatonin and photoperiodic flowering, phytomelatonin-related floral MADS-box genes, the crosstalk between phytomelatonin and phytohormones, as well as its potential applications in agriculture.

Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications; however, the rapid preparation of high-performance components remains a challenge. Herein, a novel route for 3D printing dense (< 99.4%) high-performance melt-grown alumina-mullite/glass composites using directed laser deposition (DLD) is proposed. Key issues on the composites, including phase composition, microstructure formation/evolution, densification, and mechanical properties, are systematically investigated. The toughening and strengthening mechanisms are analyzed using classical fracture mechanics, Griffith strength theory, and solid/glass interface infiltration theory. It is demonstrated that the composites are composed of corundum, mullite, and glass, or corundum and glass. With the increase of alumina content in the initial powder, corundum grains gradually evolve from near-equiaxed dendrite to columnar dendrite and cellular structures due to the weakening of constitutional undercooling and small nucleation undercooling. The microhardness and fracture toughness are the highest at 92.5 mol% alumina, with 18.39±0.38 GPa and 3.07±0.13 MPa·m1/2, respectively. The maximum strength is 310.1±36.5 MPa at 95 mol% alumina. Strength enhancement is attributed to the improved densification due to the trace silica doping and the relief of residual stresses. The method unravels the potential of preparing dense high-performance melt-grown alumina-based composites by the DLD technology.

The lateral roots of Aconitum carmichaelii, known in Chinese as fuzi, are officially recognized as a materia medica in the Chinese Pharmacopoeia and used culinarily to prepare herbal soups. A strategy combining UPLC-qToF-MS analysis of A. carmichaelii and its intraspecies and interspecies chemometrics study was developed to examine the distribution of Aconitum marker metabolites. Four diterpenoid alkaloids were recognized to be important markers in fuzi, and another 15 markers were identified to differentiate A. carmichaelii from adulterant species. The detected fuzi markers, mesaconitine (47) and hypaconitine (51), are known to be the principal toxins in this herb, while fuziline (6) and benzoylmesaconine (25) are associated with its medicinal properties. Additional marker compounds have been detected in other Aconitum species that are useful for identifying adulteration. This study provides a useful resource for detecting traditional Chinese medicine (TCM) adulterants and assisting in the quality control of botanical products in TCM and beyond.

Covering: up to 1 October 2020 Solanum steroidal glycoalkaloids (SGA), characterized by nitrogenous steroidal aglycone and glycoside residues, mainly occur in the Solanum species, including economically important edible plants such as potato, tomato, and eggplant. To date, 107 SGA assigned to six total skeletons have been identified from Solanum plants. SGA have unique structures and display significant pharmacological activities such as cytotoxic, antimicrobial, anticholesterol, and some are well-known poisons. The biosynthesis pathway, transcriptional regulation, and the evolution of SGA are also examined in detail. This report updates the chemical knowledge of the naturally occurring SGA from Solanum species, thereby providing an in-depth analysis of their diversity, biological activities, and biosynthesis.

Root-knot nematode (

While mullite is a significant oxide ceramic material, its current preparation process has many limitations such as complicated process, low efficiency, and high cost. In this paper, directed laser deposition (DLD) was used to prepare mullite ceramics directly using α-Al2O3 and SiO2 powder as raw materials. The phase composition, microstructure, and primary defects of prepared samples were investigated by XRD, Raman spectroscopy, and SEM/EDS. Vickers indentation and three-point bending experiments were used to evaluate mechanical properties. The results showed that microstructure was mainly composed of a mullite crystal phase and Si-rich glass phase. It is shown that mullite ceramics were successfully synthesized in situ during the DLD process with the use of Al2O3 and SiO2 powder. Morphology of mullite crystal inside cylindrical sample was particular “tabular cellular,” which transformed into “rod cellular” at the edge. Two mullite crystals were arranged along deposition direction basically, surrounded by the Si-rich glass phase. The defects included pores with various sizes and crack, in which large pores were mainly distributed at the edge of the sample, and small pores were throughout the section. The crack was distributed in the center of the sample and spread to the edge. Mechanical properties test showed flexural strength, microhardness, and fracture toughness were 62.8 ± 30.3 MPa, 12.7 ± 0.34 GPa, and 1.84 ± 0.14 MPa·m1/2, respectively. It is considered that pores and crack were responsible for poor mechanical properties. This research is expected to provide a new option for the rapid preparation of mullite ceramics.

Melt-grown Al2O3–ZrO2 hypoeutectic, eutectic and hypereutectic ceramics were fabricated using directed laser deposition (DLD) technology. Flexural strength of DLD-fabricated Al2O3–ZrO2 composites was obtained for the first time. Toughening mechanisms of ZrO2 in different composition ratios were revealed. The results show that hypoeutectic ceramics form composite microstructure with α-Al2O3 primary dendrites discretely distributing in eutectic continuous matrix, while the discrete phase becomes t-ZrO2 in hypereutectic ceramics. Eutectic ceramic has lamellar fine eutectic colony structure. Hypoeutectic ceramics show the best hardness, while eutectic ceramics have the highest flexural strength of 237 MPa. Fracture toughness reaches the maximum of 5.91 MPa m1/2 under hypereutectic composition, which is 16.8% higher than that of eutectic ratio. Primary t-ZrO2 dendrites in hypereutectic ceramics have phase transformation toughening effect. However, as a eutectic structure phase, t-ZrO2 in hypoeutectic and eutectic ceramics has no phase transformation toughening effect because its size is smaller than the critical size of phase transformation.

Covering: 2009 to 2018. Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, are a diverse class of compounds having complex structural features with many stereocenters. The important pharmacological activities and structural complexity of the diterpenoid alkaloids have long interested scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. Since 2009, 373 diterpenoid alkaloids, assigned to 46 skeletons, have been isolated and identified from plants mostly in the Ranunculaceae family. The names, classes, molecular weight, molecular formula, NMR data, and plant sources of these diterpene alkaloids are collated here. This review will be a detailed update of the naturally occurring diterpene alkaloids reported from the plant kingdom from 2009-2018, providing an in-depth discussion of their diversity, biological activities, pharmacokinetics, toxicity, application, evolution, and biosynthesis.

Terrestrialization is one of the most momentous events in the history of plant life, which led to the subsequent evolution of plant diversity. The transition species, in this process, had to acquire a range of adaptive mechanisms to cope with the harsh features of terrestrial environments compared to that of an aquatic habitat. As an ancient antioxidant, a leading regulator of ROS signaling or homeostasis, and a presumed plant master regulator, melatonin likely assisted plants transition to land and their adaption to terrestrial ecosystems. Two N-acetylserotonin methyltransferases (ASMT) and caffeic acid O-methyltransferases (COMT), both in the O-methyltransferase (OMT) family, catalyze the core O-methylation reaction in melatonin biosynthesis. How these two enzymes with close relevance evolved in plant evolutionary history and whether they participated in plant terrestrialization remains unknown. Using combined phylogenetic evidence and protein structure analysis, it is revealed that COMT likely evolved from ASMT by gene duplication and subsequent divergence. Newly emergent COMT gained a significantly higher ASMT activity to produce greater amounts of melatonin for immobile plants to acclimate to the stressful land environments after evolving from the more environmentally-stable aquatic conditions. The COMT genes possess more conserved substrate-binding sites at the amino acid level and more open protein conformation compared to ASMT, and getting a new function to catalyze the lignin biosynthesis. This development directly contributed to the dominance of vascular plants among the Earth's flora and prompted plant colonization of land. Thus, ASMT, together with its descendant COMT, might play key roles in plant transition to land. The current study provides new insights into the plant terrestrialization with gene duplication contributing to this process along with well-known horizontal gene transfer (HGT).

Nicotiana tabacum (tobacco) is one of the most important industrial crops and its productivity is vulnerable to drought, particularly in Yunnan province, China due to the long water-deficit spring. Here, we aimed at identifying caffeic acid O-methyltransferase (COMT) in melatonin biosynthesis to provide genetic resources against drought tolerance of tobacco. The integration of the genome-wide identification, phylogenetic relationships, and conserved domain/motif analysis revealed that NtCOMT1 could be the probable functional COMT homolog for melatonin production. In vitro enzyme activity test approved that NtCOMT1 enabled the conversion of N-acetylserotonin into melatonin, occurring both in the cytoplasm and nucleus by subcellular localization analysis. The K

Dendrobium wangliangii is an epiphytic orchid distributed in the Jinshajiang dry‐hot valley in Luquan County, Yunnan Province, China. Most Dendrobium spp. typically have a low fruit set, but this orchid shows a higher fruit set under natural conditions despite the lack of effective pollinators. The pollination biology of the critically endangered D. wangliangii was investigated in this study. A fruit set rate of 33.33 ± 4.71% was observed after bagging treatment in 2017 and a high fruit set rate (65.72 ± 4.44% in 2011; 50.79 ± 5.44% in 2017) was observed under natural conditions, indicating that D. wangliangii is characterized by spontaneous self‐pollination. The anther cap blocked the growing pollinium; thus, the pollinium slid down and reached the stigmatic cavity, leading to autogamous self‐pollination. Specifically, 51.50% of 162 unopened flowers (total 257 flowers) of this Dendrobium species under extreme water‐deficit conditions developed into fruits, suggesting the presence of cleistogamy in D. wangliangii. Here, cleistogamy may represent the primary mode of pollination for this orchid. Spontaneous self‐pollination and specific cleistogamous autogamy could represent major adaptions to the drought and pollinator‐scarce habitat in the Jinshajiang dry‐hot valley.

Pores are common defects in the process of directed laser deposition (DLD) which not only greatly reduce the fracture toughness of ceramic materials, but also lead to the failure of shaped parts. In this paper, the formation mechanism of pores was analyzed and the effects of laser power, feeding rate, scanning speed and ultrasonic power on pores were investigated. Transmission electron microscope, scanning electron microscopy observation and X-ray diffraction analysis were carried out for sample microstructure and phase composition respectively. The relative density of samples was measured by the progressive focused ion beam and the porosity was calculated by image processing software Image. The results show that the pores are divided into gas holes and shrinkage cavities. The appearance of circular gas holes with smooth inner walls are caused by the feeding method by gas forced blowing, the gas mixed with powder itself, and the gas in the molten pool formed by gasification of low-melting impurities and alumina/zirconia during laser processing. The gas holes are evenly distributed in the cross-section of the thin-walled specimen parallel to the scanning speed. As the temperature changes drastically, the material around the melt solidifies first, the melt will be attached to the solidified material to shrink, so that the melt can not be filled as a solid and finally the shrinkage cavities are formed. Generally the shrinkage cavities are irregular and the pore wall is relatively rough, mainly concentrated on the top of thin-walled samples. The laser power has the greatest influence on the pores, which has the greatest effect on the porosity but little effect on the shrinkage cavities. After attaching the ultrasound, the gas holes are mainly distributed on the top of the sample, and the shrinkage cavities almost disappear due to acoustic streaming effect of ultrasonic. When the ultrasonic power is 180 W, the porosity reaches a minimum of 0.1±0.05% and the relative density is 99.9±0.1%.

Melt growth Al2O3–ZrO2 eutectic ceramic has excellent high-temperature strength, creep resistance, oxidation resistance and ultra-high-temperature microstructural stability, which is expected to become one of the ideal high-temperature structural materials. Directed laser deposition (DLD) is a new technology for fabrication of melt growth eutectic ceramics, which can rapidly fabricate net-shaped ceramics. Aiming at decreasing crack and pore defects in samples prepared by DLD, different proportions of SiC particles (SiCp) are doped into Al2O3–ZrO2. Results show that SiCp distributes uniformly in Al2O3–ZrO2 eutectic ceramic matrix. Interfacial reaction occurs between SiCp and matrix. Two kinds of white phases rich in C, Si, Zr elements are formed around SiCp, and they are closely bonded with SiCp and matrix. The number and the maximum length of cracks in sample decrease obviously with the addition of SiCp. When the content of SiCp increases from 0 to 25 wt%, the number of cracks decreases 93% and the maximum cracks length decreases 92%. Some energy dissipation mechanisms such as crack pinning, transgranular fracture, crack deflection and bifurcation have remarkable effect on crack suppression. In addition, SiCp plays a significant role in eliminating pores, which reduces the porosity from 11.71 to 0.20%. Doping SiCp can increase the temperature and enhance the convection and disturbance of melt pool. Also, it can provide discharge channels for bubbles in melt pool.

Myrciaria cauliflora (jaboticaba) is an edible fruit common in Brazil that has been used for treating respiratory diseases, including chronic tonsillitis and asthma. This study explores the distribution of an anti-inflammatory depside, jaboticabin, in different parts of the jaboticaba plant as well as major polyphenols from the wood of jaboticaba, some with biological activity similar to jaboticabin. The peel of the fruit was found to be the major source of jaboticabin. This is the first phytochemical study of the wood of M. cauliflora. The antioxidant-activity-guided fractionation strategy successfully identified 3,3'-dimethylellagic acid-4- O-sulfate from jaboticaba wood. This ellagic acid derivative, in a manner similar to jaboticabin, showed antiradical activity and inhibited the production of the chemokine interleukin-8 after treating the human small airway epithelial cells with cigarette smoke extract. The human intestinal Caco-2 cell studies demonstrated the jaboticabin transport in vitro. The polyphenols, jaboticabin and 3,3'-dimethyellagic acid-4- O-sulfate, from jaboticaba were both found to exhibit anti-inflammatory activities, thus suggesting the potential use of these compounds or even the fruits themselves for chronic obstructive pulmonary disease.

Seed germination, an important developmental stage in the life cycle of seed plants, is regulated by complex signals. Melatonin is a signaling molecule associated with seed germination under stressful conditions, although the underlying regulatory mechanisms are largely unknown. In this study, we showed that a low concentration (10 µM or 100 µM) of melatonin had no effect on seed germination, but when the concentration of melatonin increased to 500 µM or 1000 µM, seed germination was significantly inhibited in Arabidopsis. RNA sequencing analysis showed that melatonin regulated seed germination correlated to phytohormones abscisic acid (ABA), gibberellin (GA), and auxin. Further investigation revealed that ABA and melatonin synergistically inhibited seed germination, while GA and auxin antagonized the inhibitory effect of seed germination by melatonin. Disruption of the melatonin biosynthesis enzyme gene serotonin N-acetyltransferase (SNAT) or N-acetylserotonin methyltransferase (ASMT) promoted seed germination, while overexpression of ASMT inhibited seed germination. Taken together, our study sheds new light on the function and mechanism of melatonin in modulating seed germination in Arabidopsis.

Dendrobium is a genus of flowering plants belonging to the Orchidaceae family with more than 1,400 species. Many Dendrobium species have been used as medicinal plants in several Asian countries for thousands of years. Alkaloids were reported as the major biological markers due to their complex chemical compositions and various types. In this review, we summarized the structural types of alkaloids, their pharmacological activities, as well as the mechanisms of biological activities. More than sixty alkaloids were isolated and identified from the Dendrobium genus. Moreover, the pharmacological effects of Dendrobium alkaloids as hepatic lipid and gluconeogenesis regulation, as neuroprotection, and as anti-tumor, anti-inflammatory, anti-diabetes, and anti-virus factors were described. Besides, the total chemical synthesis of dendrobine is provided, while the biosynthetic pathway of dendrobine has been proposed based on the functions of associated genes. For applications of these invaluable herbs, more researches on the extraction of biological markers from compounds are needed. Further confirmation of the proposed biosynthetic pathways is anticipated as well.

Background: The high antioxidant capacity of melatonin contributing to heavy metal tolerance for plants and animals is widely studied, while researches on microorganisms especially in filamentous fungi are rare. One typical dark septate endophyte (DSE), Exophiala pisciphila, showed significant resistance to heavy metals.Results: In this study, exogenous melatonin was verified to reduce heavy metal damage via relieving oxidative stress, activating antioxidant systems, and decreasing heavy metal accumulation in E. pisciphila. Melatonin biosynthesis enzyme genes were upregulated under heavy metal stress. Furthermore, the overexpression of E. pisciphila TDC1 (EpTDC1) and E. pisciphila ASMT1 (EpASMT1) responsible for melatonin biosynthesis in Escherichia coli and Arabidopsis thaliana, enhanced heavy metal stress tolerance for the two organisms by lowering the oxidative stress and reducing the Cd accumulation in the whole plants, especially in the roots.Conclusions: Our results indicate that melatonin confers heavy metal resistance in E. pisciphila by lowering oxidative stress and heavy metal accumulation.

BACKGROUNDRemdesivir, an inhibitor of viral RNA-dependent RNA polymerases, has been identified as a candidate for COVID-19 treatment. However, the therapeutic effect of remdesivir is controversial.METHODSWe searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials, from inception to June 11, 2020 for randomized controlled trials on the clinical efficacy of remdesivir. The main outcomes were discharge rate, mortality, and adverse events. This study is registered at INPLASY (INPLASY202060046).RESULTSData of 1075 subjects showed that remdesivir significantly increased the discharge rate of patients with COVID-19 compared with the placebo (50.4% vs. 45.29%; relative risk [RR] 1.19 [95% confidence interval [CI], 1.05–1.34], I2 = 0.0%, P = 0.754). It also significantly decreased mortality (8.18% vs. 12.70%; RR 0.64 [95% CI, 0.44–0.92], I2 = 45.7%, P = 0.175) compared to the placebo. Data of 1296 subjects showed that remdesivir significantly decreased the occurrence of serious adverse events (RR 0.77 [95% CI, 0.63–0.94], I2 = 0.0%, P = 0.716).CONCLUSIONRemdesivir is efficacious and safe for the treatment of COVID-19.TRIAL REGISTRATION NUMBERThis study is registered at the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY202060046).

Melatonin has diverse functions in plant development and stress tolerance, with recent evidence showing a beneficial role in plant biotic stress tolerance. It has been hypothesized that pathogenic invasion causes the immediate generation of melatonin, reactive oxygen species (ROS), and reactive nitrogen species (RNS), with these being mutually dependent, forming the integrative melatonin–ROS–RNS feedforward loop. Here we discuss how the loop, possibly located in the mitochondria and chloroplasts, maximizes disease resistance in the early pathogen ingress stage, providing on-site protection. We also review how melatonin interacts with phytohormone signaling pathways to mediate defense responses and discuss the evolutionary context from the beginnings of the melatonin receptor–mitogen-activated protein kinase (MAPK) cascade in unicellular green algae, followed by the occurrence of phytohormone pathways in land plants.

Dendrobium wangliangii is an endangered and epiphytic orchid with tolerance to seasonally extreme arid conditions and occurs exclusively in the hot-dry valley area of southwestern China. To reveal its molecular basis responsible for ecological adaptation, large-scale transcriptome sequencing was performed using Illumina sequencing with pooled mRNA extracted from whole plants and pseudobulbs during drought and rainy seasons. Based on the target transcript selection, the differentially expressed genes were related to 8 well-known drought-tolerant categories, and to morphological traits in resistance to water stress including pseudobulbs and roots. Further gene ontology enrichment analysis revealed that ‘nucleoside/nucleotide and ribonucleoside/ribonucleotide metabolic processes’ and ‘response to stimulus’ were the two most important aspects in resistance to drought stress with respect to the whole plant. In addition, the difference in the number and category of differentially expressed genes in whole plant and stem suggested the involvement of genes specifically localized in the stem, such as GTP-binding protein, lipases, signaling related transcripts and those involved in the ATP metabolic process. The comprehensive analysis of the epiphytic orchid in response to water deprivation indicates that integral tactics lead to active adaptation as a basal defense response to drought stress by the endangered epiphyte, including the collaboration of metabolic processes, responses to a various stimulus and other candidate genes contribute to its extreme drought tolerance. Insights from this study can be further utilized to understand stress-responsive genes in other medicinally important species and to improve the drought tolerance of food crops. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12298-018-0607-3) contains supplementary material, which is available to authorized users.

Aconitum carmichaelii has long been used as a traditional Chinese medicine, and its processed lateral roots are known commonly as fuzi. Aconitine-type C19-diterpenoid alkaloids accumulating in the lateral roots are some of the main toxicants of this species, yet their biosynthesis remains largely unresolved. As a first step towards understanding the biosynthesis of aconitine-type C19-diterpenoid alkaloids, we performed de novo transcriptome assembly and analysis of rootstocks and leaf tissues of Aconitum carmichaelii by next-generation sequencing. A total of 525 unigene candidates were identified as involved in the formation of C19-diterpenoid alkaloids, including those encoding enzymes in the early steps of diterpenoid alkaloids scaffold biosynthetic pathway, such as ent-copalyl diphosphate synthases, ent-kaurene synthases, kaurene oxidases, cyclases, and key aminotransferases. Furthermore, candidates responsible for decorating of diterpenoid alkaloid skeletons were discovered from transcriptome sequencing of fuzi, such as monooxygenases, methyltransferase, and BAHD acyltransferases. In addition, 645 differentially expressed genes encoding transcription factors potentially related to diterpenoid alkaloids accumulation underground were documented. Subsequent modular domain structure phylogenetics and differential expression analysis led to the identification of BAHD acyltransferases possibly involved in the formation of acetyl and benzoyl esters of diterpenoid alkaloids, associated with the acute toxicity of fuzi. The transcriptome data provide the foundation for future research into the molecular basis for aconitine-type C19-diterpenoid alkaloids biosynthesis in A. carmichaelii.

Directed laser deposition (DLD) has demonstrated the potential for rapid preparing high-performance melt-grown ceramics applied for the aero-engine hot section components. Mullite has excellent potential for applications in harsh environments and extreme conditions. However, there are defects (pores and cracks) in melt-grown mullite ceramics (MGMC), limiting its application, related to unclear processes, microstructure, and properties. In this work, we investigated the impact of z-increment on shaping quality, microstructure, and mechanical properties. The results reveal that oxygen vacancy concentration is responsible for the variety of sample colors. Low z-increment is beneficial to decreasing porosity, while high z-increment is beneficial to crack suppression. The formation and propagation mechanism of internal cracks at low z-increment are discussed in detail. Mullite crystals in the sample center are "tabular cellular", which are 2:1 high-alumina mullite. While mullite crystals at the sample edge are 3:2 mullite, undergo four stages as z-increment increase; "tabular cellular", "facet dendrite", "rod cellular", and mixed crystal. This evolution of crystal morphology is attributed to the decrease in temperature gradient and the increase of supersaturation. Besides, the flexural strength and microhardness increase first and then decrease with the rise of z-increment, which is the function of defects, compactness, and microstructure.

Two new C19-diterpenoid alkaloids, 7,8-epoxy-franchetine (1) and N(19)-en-austroconitine A (2), were isolated from Aconitum iochanicum. Compound 1 was a new C19-diterpenoid alkaloid with a 7,8-epoxy unit. Their structures were elucidated by comprehensive spectroscopic analyses including UV, IR, MS, 1D and 2D NMR. Biological activity tests indicated that two new compounds exhibited inhibitory activity against nitric oxide (NO) production in LPS-activated RAW264.7 macrophages. Compared with positive control, the two new compounds showed weak anti-inflammatory effects with the inhibition rate of 27.3% and 29.2%, respectively.

Melatonin can increase plant resistance to stress, and exogenous melatonin has been reported to promote stress resistance in plants. In this study, a melatonin biosynthesis-related SlCOMT1 gene was cloned from tomato (Solanum lycopersicum Mill. cv. Ailsa Craig), which is highly expressed in fruits compared with other organs. The protein was found to locate in the cytoplasm. Melatonin content in SlCOMT1 overexpression transgenic tomato plants was significantly higher than that in wild-type plants. Under 800 mM NaCl stress, the transcript level of SlCOMT1 in tomato leaf was positively related to the melatonin contents. Furthermore, compared with that in wild-type plants, levels of superoxide and hydrogen peroxide were lower while the content of proline was higher in SlCOMT1 transgenic tomatoes. Therefore, SlCOMT1 was closely associated with melatonin biosynthesis confers the significant salt tolerance, providing a clue to cope with the growing global problem of salination in agricultural production.

In the era of information, recommender systems are playing an indispensable role in our lives. A lot of deep learning based recommender systems have been created and proven to be good progress. However, users’ decisions are determined by both long-term and short-term preferences, and most of the existing efforts study these two requirements separately. In this paper, we seek to build a bridge between the long-term and short-term preferences. We propose a Long & Short-term Preference Model (LSPM), which incorporates LSTM and self-attention mechanism to learn the short-term preference and jointly model the long-term preference by a neural latent factor model. We conduct experiments to demonstrate the effectiveness of LSPM on three public datasets. Compared with the state-of-the-art methods, LSPM got a significant improvement in HR@10 and NDCG@10, which relatively increased by \(3.875\%\) and \(6.363\%\). We publish our code at https://github.com/chenjie04/LSPM/.

Al2O3/Al6Ti2O13 composite ceramics with low thermal expansion properties are promising for the rapid preparation of large-scale and complex components by directed energy deposition-laser based (DED-LB) technology. However, the wider application of DED-LB technology is limited due to the inadequate understanding of process conditions. The shaping quality, microstructure, and mechanical properties of Al2O3/Al6Ti2O13 (6 mol% TiO2) composite ceramics were systematically investigated as a function of energy input in an extensive process window. On this basis, the formation mechanism of solidification defects and the evolution process of microstructure were revealed, and the optimized process parameters were determined. Results show that high energy input improves the fluidity of the molten pool and promotes the uniform distribution and full growth of constituent phases, thus, facilitating the elimination of solidification defects, such as pores and strip gaps. In addition, the microstructure size is strongly dependent on the energy input, increasing when the energy input increases. Moreover, the morphology of the α-Al2O3 phase gradually transforms from cellular into cellular dendrite with increasing energy input due to changing solidification conditions. Under the comprehensive influence of solidification defects and microstructure size, the fracture toughness and flexural strength of Al2O3/Al6Ti2O13 composite ceramics present a parabolic law behavior as the energy input increases. Optimal shaping quality and excellent mechanical properties are achieved at an energy input range of 0.36−0.54 W*min2 g−1 mm−1. Within this process window, the average microhardness, fracture toughness, and flexural strength of Al2O3/Al6Ti2O13 composite ceramics are up to 1640 Hv, 3.87 MPa m1/2, and 227 MPa, respectively. This study provides practical guidance for determining the process parameters of DED-LB of melt growth Al2O3/Al6Ti2O13 composite ceramics.

Directed energy deposition (DED) has developed rapidly in recent years as a new material-structure integration manufacturing technology for preparing melt-growth ceramics. However, the influence of process conditions on the forming quality has not been systematically studied. Alumina/aluminum titanate composite ceramics were directly prepared using DED technology with an extensive process window. The effects of the scanning speed on the typical defects, microstructure, and mechanical properties of prepared samples were systematically investigated, and the optimized process parameters were determined. Results show that the scanning speed has a significant effect on the macroscopic defects, such as cracks and pores, microstructure characteristics, such as grain morphology and size, and mechanical properties, such as flexural strength. Slow-speed scanning achieved a longer retention time of the liquid molten pool, which was beneficial to pore suppression. Rapid scanning reduced the temperature gradient at the bottom of the molten pool to obtain crack-free samples. The directional growth tendency of α-Al2O3 cellular dendrites that were discretely distributed in the Al6Ti2O13 matrix phase weakened, and the secondary dendrites gradually developed by increasing the scanning speed. This phenomenon was attributed to the change of the heat-dissipation direction and the solidification rate of solid/liquid interface caused by the scanning speed. Moreover, the fracture toughness of the prepared samples gradually increased as the scanning speed increased, while the flexural strength showed a parabolic law behavior. The trend of the properties was due to microstructure refinement and macroscopic defects. Generally, the optimal forming quality was achieved at a scanning speed of 300−500 mm/min. Within this process window, the sample had up to 98 % densification, 1640 Hv hardness, 3.75 MPa m1/2 fracture toughness, and 212 MPa flexural strength.

Plant hormone candidate melatonin has been widely studied in plants under various stress conditions, such as heat, cold, salt, drought, heavy metal, and pathogen attack. Under stress, melatonin usually accumulates sharply by modulating its biosynthesis and metabolic pathways. Beginning from the precursor tryptophan, four consecutive enzymes mediate the biosynthesis of tryptamine or 5-hydroxytryptophan, serotonin, N-acetylserotonin or 5-methoxytryptamine, and melatonin. Then, the compound is catabolized into 2-hydroxymelatonin, cyclic-3-hydroxymelatonin, and N1-acetyl-N2-formyl-5-methoxyknuramine through 2-oxoglutarate-dependent dioxygenase catalysis or reaction with reactive oxygen species. As an ancient and powerful antioxidant, melatonin directly scavenges ROS induced by various stress conditions. Furthermore, it confreres stress tolerance by activating the plant’s antioxidant system, alleviating photosynthesis inhibition, modulating transcription factors that are involved with stress resisting, and chelating and promoting the transport of heavy metals. Melatonin is even proven to defense against pathogen attacks for the plant by activating other stress-relevant hormones, like salicylic acid, ethylene, and jasmonic acid. Intriguingly, other precursors and metabolite molecules involved with melatonin also can increase stress tolerance for plant except for unconfirmed 5-methoxytryptamine, cyclic-3-hydroxymelatonin, and N1-acetyl-N2-formyl-5-methoxyknuramine. Therefore, the precursors and metabolites locating at the whole biosynthesis and catabolism pathway of melatonin could contribute to plant stress resistance, thus providing a new perspective for promoting plant stress tolerance.

Acetylserotonin methyltransferase (ASMT) is the last enzyme of melatonin biosynthesis and may play a rate-limiting role in the melatonin production of plants. In this study, systematic analysis of the ASMT gene family in tomato (Solanum lycopersicum Mill) has been presented by the integration of the structural features, phylogenetic relationships, exon/intron configuration, and expression profile during growth and development, as well as biotic stresses. The results revealed that the tomato genome encoded a minimum of 14 members, containing three probable encoded pseudogenes. Chromosome mapping indicated that the family had probably expanded via tandem duplication events. Genome-wide RNA-seq and qRT-PCR based gene expression analysis revealed that almost half of the SlASMT genes were expressed in at least one of the experimental stages studied and also showed differential accumulation. Furthermore, the tandem duplicated SlASMT genes showed differential expression levels, which indicated probable functional divergence during the course of the evolution. Finally, this study also determined that some SlASMT genes were induced by multiple pathogens. The results suggested that these genes could be involved in tomato plant response to biotic stresses.

Aconitum carmichaelii has long been used as a traditional Chinese medicine, and its processed lateral roots are known commonly as fuzi. Aconitine-type C

Dendrobium wangliangii is seriously threatened because of anthropogenic and environmental pressures. A protocol with seed asymbiotic germination was developed to conserve the orchid in vitro. The germination rate was 92% under 16/8 h (light/dark) photoperiod after 240 days from hand-pollination in a modified medium. Polyembryony was founded in D. wangliangii, with a percentage of 0.87%. Half MS promoted the protocorms proliferation well, with the protocorms differentiated at the frequency of 28.79% when cultured on half MS, supplemented with 2 mg L-1 6-benzylaminopurine (BA) and 0.1 mg L-1naphthaleneacetic acid (NAA). Additives, especially 100 ml L-1 coconut milk (CM), improved the protocorm differentiation greatly but led to a lethality of 49.92%. The pretreatment of 1 mg L-1 GA3 for 15 days, after inoculated to the medium amended with 2 mg L-1 BA, 0.1 mg L-1 NAA and 100 ml L-1 CM, increased the differentiation to 54.68%. The combination of 2 mg L-1 BA, 0.1 mg L-1 NAA, and 100 ml L-1 CM also showed an efficient role in adventitious bud multiplication. CM effectively controlled the albino phenotype. In addition, inflorescence induction (100%) was produced with 2 mg L-1 1-phenyl-3-(1, 2, 3-thiadiazol-5-yl)-urea (TDZ) and the best flower development was obtained with 0.3 mg L-1 paclobutrazol (PP333), and 0.5 mg L-1 NAA. Key words: Dendrobium wangliangii, micropropogation, asymbiotic germination, adventitious buds multiplication, polyembryony, in vitro flowering.