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Background Low temperature (LT) often occurs at the seedling stage in the early rice-growing season, especially for direct seeded early-season indica rice, and using flooding irrigation can mitigate LT damage in rice seedlings. The molecular mechanism by which flooding mitigates the damage induced by LT stress has not been fully elucidated. Thus, LT stress at 8 °C, LT accompanied by flooding (LTF) and CK (control) treatments were established for 3 days to determine the transcriptomic, proteomic and physiological response in direct seeded rice seedlings at the seedling stage. Results LT damaged chloroplasts, and thylakoid lamellae, and increased osmiophilic bodies and starch grains compared to CK, but LTF alleviated the damage to chloroplast structure caused by LT. The physiological characteristics of treated plants showed that compared with LT, LTF significantly increased the contents of rubisco, chlorophyll, PEPCK, ATP and GA3 but significantly decreased soluble protein, MDA and ABA contents. 4D-label-free quantitative proteomic profiling showed that photosynthesis-responsive proteins, such as phytochrome, as well as chlorophyll and the tricarboxylic acid cycle were significantly downregulated in LT/CK and LTF/CK comparison groups. However, compared with LT, phytochrome, chlorophyllide oxygenase activity and the glucan branching enzyme in LTF were significantly upregulated in rice leaves. Transcriptomic and proteomic studies identified 72,818 transcripts and 5639 proteins, and 4983 genes that were identified at both the transcriptome and proteome levels. Differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were significantly enriched in glycine, serine and threonine metabolism, biosynthesis of secondary metabolites, glycolysis/gluconeogenesis and metabolic pathways. Conclusion Through transcriptomic, proteomic and physiological analyses, we determined that a variety of metabolic pathway changes were induced by LT and LTF. GO and KEGG enrichment analyses demonstrated that DEGs and DEPs were associated with photosynthesis pathways, antioxidant enzymes and energy metabolism pathway-related proteins. Our study provided new insights for efforts to reduce the damage to direct seeded rice caused by low-temperature stress and provided a breeding target for low temperature flooding-resistant cultivars. Further analysis of translational regulation and metabolites may help to elucidate the molecular mechanisms by which flooding mitigates low-temperature stress in direct seeded early indica rice at the seedling stage.

Long-term straw return is an important carbon source for improving soil organic carbon (SOC) stocks in croplands, and straw removal through burning is also a common practice in open fields in South China. However, the specific effects of long-term rice straw management on SOC fractions, the related enzyme activities and their relationships, and whether these effects differ between crop growing seasons remain unknown. Three treatments with equal nitrogen, phosphorus, and potassium nutrient inputs, including straw/ash and chemical nutrients, were established to compare the effects of straw removal (CK), straw return (SR), and straw burned return (SBR). Compared to CK, long-term SR tended to improve the yield of early season rice (P=0.057), and significantly increased total organic carbon (TOC) and microbial biomass carbon (MBC) in double-cropped rice paddies. While SBR had no effect on TOC, it decreased light fraction organic carbon (LFOC) in early rice and easily oxidizable organic carbon (EOC) in late rice, significantly increased dissolved organic carbon (DOC), and significantly decreased soil pH. These results showed that MBC was the most sensitive indicator for assessing changes of SOC in the double-cropped rice system due to long-term straw return. In addition, the different effects on SOC fraction sizes between SR and SBR were attributed to the divergent trends in most of the soil enzyme activities in the early and late rice that mainly altered DOC, while DOC was positively affected by β-xylosidase in both early and late rice. We concluded that straw return was superior to straw burned return for improving SOC fractions, but the negative effects on soil enzyme activities in late rice require further research.

The photosynthesis, photomorphogenesis, and photoperiod processes in plants are regulated according to light intensity and quality. The aim of this study was to investigate the effects of different light qualities on eggplant seedlings and determine the best light quality for growth. The seedlings of eggplant cultivar ‘Jingqiejingang’ were grown under light-emitting diodes (LEDs): white (W, the control), red (R), blue (B), and different ratios of B/R lights (B/R = 1/1, B/R = 1/3, B/R = 1/6, B/R = 1/9). The growth parameters, leaf morphology, photosynthetic performance, chlorophyll fluorescence, and the carbon and nitrogen metabolism in the leaves of eggplant seedlings under different LED light treatments were studied. The results showed that the plant height, leaf development, and photosynthetic characteristics were inhibited by red light but elevated by blue light compared with the control. Conversely, the contents of chlorophyll a, chlorophyll b, and carotenoids were all increased by red light, while decreased by blue light significantly. In addition, the contents of carbohydrates and the activities of nitrogen assimilation enzymes were not or little changed by the monochromatic blue and red light. The combined light of red and blue were more beneficial for growth than the monochromatic light, especially B/R = 1/3 light. Under B/R = 1/3 light, the parameter values of plant growth, leaf development, photosynthetic pigments and characteristics, and carbon and nitrogen metabolism were all maximum. Taken together, combined application lights of red and blue are good practice for the cultivation of eggplant seedlings, and LED B/R = 1/3 light was optimum.

Lateral branches (LBs) pruning is performed frequently to keep the tomato plants in optimal growth conditions. However, the suitable pruning length of LBs, as well as the physiological and molecular mechanisms of pruning length on plant growth regulation remains elusive in tomato. The effects of pruning length of LBs from 0 to 20 cm on vegetative growth, reproductive growth, labor costs, hormone metabolism and genes transcripts were evaluated in an indeterminate type tomato cultivar. By comprehensive analysis, we provided evidence that pruning length of LBs at about 6–7 cm was suitable for plant growth, high yield, and low labor costs in tomato production. For mechanisms, appropriate extension of pruning length of LBs increased indole acetic acid (IAA) concentrations in root, which promoted the biosynthesis and upward transport of inactive cytokinins (CKs), as well as root development. Meanwhile, existence of LBs inhibited the auxin outflow of the lower flower stalks by regulating transcripts of AUX1 and PIN. Then, the enhanced concentrations of IAA and CKs in ovary could promote fruit swelling. Additionally, pruning length of LBs also influenced the leaf senescence to control photosynthesis. Taken together, we highlight that pruning length of LBs influence auxin and cytokinins homeostasis in relation to growth and yield in tomato plants.

Bacterial therapy, which targets the tumor site and aims at exerting an antitumor immune response, has displayed a great potential against malignant tumors. However, failure of the phase I clinical trial of Salmonella strain VNP20009 alone demonstrates that bacterial treatment alone can unsatisfy the requirements of high efficiency and biosafety. Herein, a strategy of both-in-one hybrid bacteria is proposed, wherein the chemotherapeutic drug doxorubicin (DOX) is integrated onto the surface of glucose dehydrogenase (GDH)-overexpressed non-pathogenic Escherichia coli (E. coli) strain, to potentiate the antitumor efficacy. Nicotinamide adenine dinucleotide phosphate (NADPH), which is produced by GDH from E. coli, promotes the generation of toxic reactive oxygen species (ROS) within the tumor, and ROS is then catalyzed by the DOX-activated NADPH oxidases. Importantly, the hybrid bacteria enhance stimulated systemic antitumor immune responses, thereby leading to effective tumor eradication. When this strategy is applied in four different tumor models, the hybrid bacteria significantly inhibited tumor metastasis, postsurgical regrowth, and primary/distal tumor relapse. The both-in-one ROS-immunity-boosted hybrid bacteria strategy provides knowledge for the rational design of bacteria-based synergistic cancer therapy.

In this study, the protective role of exogenous ascorbic acid (AsA) on salt-induced inhibition of photosynthesis in the seedlings of processing tomatoes under salt stress has been investigated. Plants under salt stress (NaCl, 100 mmol/L) were foliar-sprayed with AsA (0.5 mmol/L), lycorine (LYC, 0.25 mmol/L, an inhibitor of key AsA synthesis enzyme l-galactono-γ-lactone dehydrogenase activity), or AsA plus LYC. The effects of AsA on fast OJIP fluorescence rise curve and JIP parameters were then examined. Our results demonstrated that applying exogenous AsA significantly changed the composition of O-J-I-P fluorescence transients in plants subjected to salt stress both with and without LYC. An increase in basal fluorescence (Fo) and a decrease in maximum fluorescence (Fm) were observed. Lower K- and L-bands and higher I-band were detected on the OJIP transient curves compared, respectively, with salt-stressed plants with and without LYC. AsA application also significantly increased the values of normalized total complementary area (Sm), relative variable fluorescence intensity at the I-step (VI), absorbed light energy (ABS/CSm), excitation energy (TRo/CSm), and reduction energy entering the electron transfer chain beyond QA (ETo/CSm) per reaction centre (RC) and electron transport flux per active RC (ETo/RC), while decreasing some others like the approximated initial slope of the fluorescence transient (Mo), relative variable fluorescence intensity at the K-step (VK), average absorption (ABS/RC), trapping (TRo/RC), heat dissipation (DIo/RC) per active RC, and heat dissipation per active RC (DIo/CSm) in the presence or absence of LYC. These results suggested that exogenous AsA counteracted salt-induced photoinhibition mainly by modulating the endogenous AsA level and redox state in the chloroplast to promote chlorophyll synthesis and alleviate the damage of oxidative stress to photosynthetic apparatus. AsA can also raise the efficiency of light utilization as well as excitation energy dissipation within the photosystem II (PSII) antennae, thus increasing the stability of PSII and promoting the movement of electrons among PS1 and PSII in tomato seedling leaves subjected to salt stress.

Melatonin is a natural phytohormone that occurs in most plants. It can regulate not only plant growth and development but also alleviate biotic and abiotic stress in plants. However, no studies have reported on endogenous melatonin increasing tomato tolerance to salt stress. In the present study, we observed that the overexpression of caffeic acid O-methyltransferase 1 (SlCOMT1) increased melatonin levels in tomato plants. We also observed that transgenic plants exhibited higher salt stress tolerance. SlCOMT1 overexpression could maintain the balance of Na+/K+ and decrease ion damage by activating salt overly sensitive (SOS) pathway under salt treatment. In addition, SlCOMT1 overexpression significantly enhanced the antioxidant capability, with higher antioxidant enzyme activity observed, including superoxide dismutase, peroxide and catalase activity, and higher ascorbic acid (AsA) and glutamate (GSH) accumulation levels. SlCOMT1 overexpression also maintained good nutrient homeostasis in the tomato plants. In addition, SlCOMT1 overexpression upregulated some stress-related genes (AREB1, AIM1, MAPK1, WRKY33 and CDPK1), which resulted in the activation of downstream signaling pathways and could be partly responsible for the improvement in salt stress tolerance.

Melatonin (Mel) serves as an important signalling molecule in various aspects of stress tolerance in plants. However, the function of Mel in pesticide metabolism remains unknown. Here, selecting the widely used fungicide carbendazim (MBC) as the model, we found that exogenous Mel had the ability to alleviate pesticide phytotoxicity and residues in tomato as well as in some other vegetables. Additionally, overexpression of the Mel biosynthetic gene caffeic acid O-methyltransferase 1 (COMT1) significantly enhanced the capacity of the tomato to reduce MBC phytotoxicity and residue. This outcome was mainly because of the Mel-induced antioxidant capability, as well as the key detoxification process. Indeed, levels of reactive oxygen species (ROS) and lipid peroxides significantly decreased after applying exogenous Mel or overexpressing COMT1, which resulted from direct ROS scavenging, and increased Mel levels significantly enhanced antioxidant enzymatic activity. More importantly, Mel activated the ascorbate-glutathione cycle to participate in glutathione S-transferase-mediated pesticide detoxification. A grafting experiment showed that rootstocks from COMT1 transgenic plants increased the Mel accumulation of wild-type scions, resulting in MBC metabolism in the scions. To our knowledge, this is the first report providing evidence of Mel-induced pesticide metabolism, which provides a novel approach for minimizing pesticide residues in crops by exploiting plant self-detoxification mechanisms.

Melatonin plays important roles in multiple stress responses. However, the downstream signaling pathway and molecular mechanism are unclear until now. Here, we not only revealed the transcriptional control of melatonin-induced sodic alkaline stress tolerance, but also described a screen for key downstream transcriptional factors of melatonin through transcriptome analysis. The melatonin-induced transcriptional network of hormone, transcriptional factors and functional genes has been established under both control and stress conditions. Among these, six candidates of transcriptional factors have been identified via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis. Using the virus-induced gene silencing approach, we confirmed that DREB1α and IAA3 were key downstream transcriptional factors of melatonin-induced sodic alkaline stress tolerance at the genetic level. The transcriptions of DREB1α and IAA3 could be activated by melatonin or sodic alkaline treatment. Interestingly, we found that DREB1α could directly upregulate the expression of IAA3 by binding to its promoters. Moreover, several physiological processes of Na+ detoxification, dehydration resistance, high pH buffering and reactive oxygen species scavenging were confirmed to depend or partly depend on DREB1α and IAA3 pathway in melatonin-induced stress tolerance. Taken together, this study suggested that DREB1α and IAA3 are positive resistant modulators, and provided a direct link among melatonin, DREB1α and IAA3 in the sodic alkaline stress tolerance activating in tomato plants.

High-quality rice varieties are planted widely in southern China. However, the changes in grain quality in the different high-quality rice varieties released in recent years are unclear. This study compared the grain quality changes and status of those varieties and presented proposals for future breeding. In the past 11 years, high-quality indica has significantly improved chalky rice rate (CRR), chalkiness degree (CD) but decreased head rice rate (HRR); amylose content (AC), gel consistency (GC) and length-to-width ratio (LWR) were improved only in indica hybrid rice. Most high-quality rice varieties grown in southern China are primarily indica rice. In contrast to indica rice, japonica rice had increased milling recovery, cooking and eating qualities (CEQ), but worsened significantly the physical appearance. For japonica rice, hybrid varieties exhibited a marked improvement in the rice quality for lower AC, higher GC and LWR compared with inbred varieties. A higher grain quality was observed in inbred varieties for indica rice due to lower CRR, CD and AC, higher HRR and GC. Our results suggested that we should be focused on improving the physical appearance quality for japonica rice and milling recovery, particularly CEQ for indica rice, for future high-quality rice breeding.

How to develop a simple and economic approach to improve plant cold stress tolerance is an important scientific problem. With the hope that we explored the effect and metabolism of cold plasma (CP) seed treatment on the chilling tolerance in tomato plants. 75 W CP seed treatment showed the best mitigative effect on cold-induced injury of tomato seedlings, as evidenced by the higher maximum photochemical efficiency of PSII (Fv/Fm), lower ion leakage and chilling injury index. Moreover, the results showed that CP-induced chilling tolerance was related to the hydrogen peroxide (H2O2) mediated by respiratory burst oxidase homologue 1 (RBOH1), which was proved by the decrease low temperature tolerance observed in RBOH1 silence or chemical scavenging of H2O2 seedlings. Furthermore, RBOH1-mediated H2O2 acted as the downstream signaling of CP treatment to enhance the levels of abscisic acid (ABA) by increasing the transcript of 9-cis-epoxycarotenoid dioxygenase 1 (NCED1). Mutation of NCED1 completely abolished CP-induced cold resistance. Genetic evidence showed that H2O2 and ABA were positive regulators of cold stress tolerance. Thus, CP-induced H2O2 and ABA cascade signal up-regulated the regulatory genes (ICE1 and CBF1) of cold acclimation, which increased the osmotic adjustment substances (proline and soluble sugar) accumulation and antioxidant enzymes (SOD, APX and CAT) activities. Our results indicate that H2O2 and ABA signals are involved in conferring cold stress tolerance induced by CP seed treatment in tomato plants.

It has been found that the quality of oocytes from obese women has been compromised and subsequent embryos displayed arrested development. The compromised quality may be either due to the poor or rich metabolic conditions such as imbalance or excession of lipids during oocyte development. Generally, lipids are mainly stored in the form of lipid droplets and are an important source of energy metabolism. Similarly, lipids are also essential signaling molecules involved in various biological cascades of oocyte maturation, growth and oocyte competence acquisition. To understand the role of lipids in controlling the oocyte development, we have comprehensively and concisely reviewed the literature and described the role of lipid metabolism in oocyte quality and maturation. Moreover, we have also presented a simplified model of fatty acid metabolism along with its implication on determining the oocyte quality and cryopreservation for fertilization.

The effects of water irrigation management including conventional irrigation (CK), constant flooding irrigation (CFI) and alternate wetting and drying (AWD) on starch structure and physicochemical properties of two indica rice cultivars with good- and poor-quality were evaluated in the field condition with two years. The results showed that AWD could significantly increase peak viscosity, breakdown and gelatinization temperature, decreased setback and gelatinization enthalpy in two indica rice cultivars. However, starch granule size and amylopectin chain length distribution were differed the trends in the rice cultivars and treatments. AWD reduced starch granules size and amylopectin short chain, especially for large starch granules, but increased medium and long chain, which might contribute to better thermal stability and pasting viscosity for good-quality cultivar. Our study indicated that water irrigation management affected starch structure and physicochemical properties of indica rice starch, and would provide favorable information for improvement of rice starch in food industry.

Auxin and cytokinin are two kinds of important phytohormones that mediate outgrowth of axillary buds in plants. How nitric oxide and its regulator of S-nitrosoglutathione reductase (GSNOR) take part in auxin and cytokinin signaling for controlling axillary buds outgrowth remains elusive. We investigated the roles of GSNOR during tomato axillary bud outgrowth by using physiological, biochemical and genetic approaches. GSNOR negatively regulated NO homeostasis. Suppression of GSNOR promoted axillary bud outgrowth by inhibiting the expression of FZY in both apical and axillary buds. Meanwhile, AUX1 and PIN1 were down-regulated in apical buds but up-regulated in axillary buds in GSNOR-suppressed plants. Thus, reduced IAA accumulation was shown in both apical buds and axillary buds of GSNOR-suppressed plants. GSNOR-mediated changes of NO and auxin affected cytokinin biosynthesis, transport, and signaling. And a decreased ratio of auxin: cytokinin was shown in axillary buds of GSNOR-suppressed plants, leading to bud dormancy breaking. We also found that the original NO signaling was generated by nitrate reductase (NR) catalyzing nitrate as substrate. NR-mediated NO reduced the GSNOR activity through S-nitrosylation of Cys-10, then induced a further NO burst, which played the above roles to promote axillary buds outgrowth. Together, GSNOR-mediated NO played important roles in controlling axillary buds outgrowth by altering the homeostasis and signaling of auxin and cytokinin in tomato plants.

2-Arylpropionic acid derivatives, such as ibuprofen, constitute an important group of non-steroidal anti-inflammatory drugs (NSAIDs). Biocatalytic asymmetric reduction of 2-arylacrylic acid derivatives by ene reductases (EREDs) is a valuable approach for synthesis of these derivatives. However, previous bioreduction of 2-arylacrylic acid derivatives by either ERED wild-types or variants resulted solely in nonpharmacological (R)-enantiomers as the products. Here, we present the engineering of Saccharomyces pastorianus old yellow enzyme 1 (OYE1) into (S)-stereoselective enzymes, which afford pharmacologically active (S)-profen derivatives. By structural comparison of substrate recognition in related EREDs and analysis of non-covalent contacts in the pro-S model of OYE1, the key residues of OYE1 that switch its stereoselectivity to an (S)-stereopreference were identified. Systematic site-directed mutagenesis screening at these positions successfully provided the (S)-stereoselective OYE1 variants, which catalyzed stereoselective bioreduction of various profen precursors to afford pharmacologically active (S)-derivatives including (S)-ibuprofen and (S)-naproxen methyl esters with up to >99% ee values. Moreover, the key residues and mutation strategy obtained from OYE1 could be further transferred to OYE 2.6 (from Pichia stipitis) and KnOYE1 (from Kazachstania naganishii) to create the (S)-stereoselective EREDs. Our results may provide a generalizable strategy for stereocontrol of OYEs and set the basis for biocatalytic production of (S)-profens.

A cadmium (Cd) stress test was carried out on Eisenia fetida in artificial soil. Six Cd concentration gradient solutions (0, 50, 100, 125, 250 and 500 mg/kg) were prepared. Two treatment groups, short-term stress and long-term stress, were established. The former lasted for 10 days, and the latter lasted for 30 days. The Biolog ECO-microplate culture method was used to determine the utilization of the 31 carbon sources by the microbes in earthworm homogenate. The total protein content (TP), peroxidase activity (POD), catalase activity (CAT), superoxide dismutase activity (SOD), glutathione peroxidase activity (GPX), glutathione-S-transferase activity (GST), malondialdehyde content (MDA) and acetylcholinesterase activity (AChE) in earthworm were determined in order to investigate the regulation of oxidative stress and the functional diversity of microbial communities in earthworms under Cd stress. By combining the entropy weight method (EW) and the technique for order preference by similarity to an ideal solution model (TOPSIS), the physiological functional indices of earthworms were assessed objectively and scientifically, and the physiological changes under the different stress periods were evaluated. The results showed that a Cd-tolerant dominant population appeared in the microbial community under Cd stress. In the short-term test, oxidative stress were more effective in coping with Cd stress than the microbial community, and oxidative stress regulated the microbial community functional diversity. Under long-term Cd stress, the regulatory effect was weak or non-existent. In this study, a new evaluation model was established to explore the regulation process of earthworm on its oxidation stress and the functional diversity of microbial communities under Cd stress, and provide a theoretical basis for revealing the detoxification mechanism of earthworms.

Since the first discovery of old yellow enzyme 1 (OYE1) from Saccharomyces pastorianus in 1932, biocatalytic asymmetric reduction of activated alkenes by OYEs has become a valuable reaction in organic synthesis. To access stereocomplementary C=C-bond bioreduction, the mining of novel OYEs and especially the protein engineering of existing OYEs have been performed, which successfully achieved the stereocomplementary reduction in several cases and further raise the potential of applications. In this review, we analyzed the structures, active sites, and substrate recognition of OYEs, which are the bases for their substrate specificity and stereospecificity. Sequence similarity network of OYEs superfamily was also constructed to investigate the scope of characterized OYEs. The structure-guided engineering to switch the stereoselectivity of OYEs and thus access stereocomplementary bioreduction over the last decade (2009-2020) was then reviewed and discussed, which might give new insights into the mining and engineering of related biocatalysts. KEY POINTS: • The sequence similarity network of OYEs superfamily was constructed and annotated. • The structures and active sites of OYEs from different classes were compared. • "Left/right" binding mode was used to explain the stereopreferences of OYEs. • Structure-guided engineering of OYEs to switch their stereoselectivity was reviewed.

The present study was conducted to investigate the effectiveness of Streptomyces (GLY-P2) in degradation of ferulic acid (FA) and p-hydroxybenzonic acid (PHBA) in the rhizosphere of cucumbers by assaying the alteration of antioxidant enzymes activities and rhizospheric microbial community. GLY-P2 was isolated, identified as Streptomyces canus, and applied to cucumber-planted soil containing FA and PHBA. Optimal conditions for FA and PHBA degradation by GLY-P2 were 40 °C, pH 7, and 0.2 g l−1 mixture of FA and PHBA. During the degradation, vanillin, vanillic acid, and protocatechoic acid were metabolites; and activities of superoxide dismutase (SOD), catalase, ascorbate peroxidase (APX), and dehydroascorbate reductase in GLY-P2 were induced. When inoculated into cucumber-planted soil containing 220 μg g−1 mixture of FA and PHBA, GLY-P2 degraded FA and PHBA in soil, improved plant growth, and decreased malonaldehyde, superoxide radical, and hydrogen peroxide levels in leaves. GLY-P2 also enhanced activities of SOD, catalase, glutathione peroxidase, APX, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, increased contents of ascorbate and glutathione, and elevated transcript levels of copper/zinc SOD, manganese SOD, catalase, and APX in leaves. Moreover, GLY-P2 changed soil bacterial richness, diversity, and community composition, and increased phosphatase, catalase, urease, and sucrase activities in rhizospheric soil. GLY-P2 mitigates FA and PHBA stress in cucumber by activating leaf antioxidant enzymes and affecting soil bacterial community.

The selection of salt-tolerant watermelon rootstocks requires the evaluation of its underlying mechanism. The present study investigated the effect of applying 200 mmol·L−1 NaCl on various physiological and biochemical parameters of Citrullus lanatus ‘Jingxin No.2’ (abbreviated as W) seedlings grafted onto W, Cucurbita moschata ‘Quanneng Tiejia’ (P1), ‘Kaijia No.1’ (P2), and Lagenaria siceraria ‘Hanzhen No.3’ (G), which were grown hydroponically. All the measured growth parameters were significantly inhibited by salt stress, with W/P2 exhibiting superior growth. Salt stress increased Na+ uptake, which in turn disrupted K+/Na+ homeostasis in all grafting combinations. The photosynthetic capacity, chlorophyll concentration, and photochemical efficiency of photosystem II of all grafts significantly decreased with salt stress. However, W grafted onto G and P2 showed higher resistance than W grafted onto W and P1. Electrolyte leakage (EL) superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase activity were significantly affected by both grafting and salt stress. Minimum EL was observed in W/P2, which also exhibited superior antioxidative capacity. Physiological and biochemical assessment indicated that W grafted onto the P2 rootstock displayed the greatest salt tolerance. Plants grafted onto salt-resistant P2 accumulated less Na+ and reactive oxygen species (ROS) and exhibited superior growth, photosynthesis, and ROS-scavenging capacity compared to those grafted onto the other rootstocks. Keywords: watermelon, rootstock, grafting, salt stress, physiological response

We describe a facile method to synthesize a new type of catalyst by electrodepositing Ag nanocrystals (AgNCs) on the different polymer dyes, Poly (methylene blue) (PMB) or Poly (4-(2-Pyridylazo)-Resorcinol) (PAR) modified graphene‑carbon spheres (GS) hybrids. The self-assembled GS take dual advantages of carbon spheres and graphene. Carbon spheres acts as nano-spacers prevent the aggregation of graphene and guarantee the fast electron transfer of GS. Secondly, polymerized dyes used here are beneficial for AgNCs growing as a linker. The effects of dyes on the growth habits, morphologies and catalytic properties for AgNCs were investigated. A novel electrochemical nonenzymatic sensor for hydrogen peroxide (H2O2) detection is fabricated based on the Ag/Polymer dyes/GS ternary composites modified glass carbon electrode (GCE) for the first time. It was found that the proposed electrodes, especially for Ag/PMB/GS/GCE, displayed a peculiar electrocatalytic activity towards H2O2 reduction synergistically as compared to Ag/PAR/GS/GCE or Ag/GS/GCE alone. Ag/PMB/GS/GCE showed a linear response over the H2O2 concentration range of 0.5 to 1112 μM. The detection limit and sensitivity is 0.15 μM and 400 μA mM−1 cm−2, respectively. These outstanding results enable the practical application of Ag/PMB/GS/GCE for the H2O2 tracking released from MCF-7 (human breast cancer cells) with satisfactory results.

Xanthine dehydrogenase (XDH) is a crucial enzyme involved in purine metabolism. To evaluate the effect of XDH deficiency on rice growth during dark treatment, wild type (WT) Nipponbare (Oryza sativa L.) and two independent transgenic lines with severe RNAi suppression (xdh3 and xdh4) were used in the present experiment. Under normal growth conditions, chlorophyll levels and biomass were indistinguishable between WT and the two RNAi transgenic lines, but XDH enzyme activity and ureide levels were suppressed in XDH RNAi transgenic lines. When XDH RNAi transgenic lines were subjected to dark treatment, chlorophyll content and biomass were significantly decreased, while O2–· production rate and malonaldehyde (MDA) were significantly increased compared to WT. The spraying test of exogenous allantoin raised chlorophyll content and biomass and reduced O2–· production rate and MDA in WT and both transgenic lines, and it also simultaneously reduced differences between RNAi and WT plants caused by XDH deficiency in growth potential and anti-oxidative capacity under dark treatment. These results suggested that fully functional purine metabolism plays an important role in reducing the sensitivity of rice seedlings to dark stress.

Although various works have been done in alleviating effects of exogenous salicylic acid (SA) on abiotic stress in plants, it was not reported whether exogenous SA had effects on alkaline-tolerance of plants. In the present study, we found that the effect of exogenous SA depended on the concentration and 75 μM SA showed the best remission effect on cucumber plants under alkaline stress. The effect of 75 μM SA on detailed change of photosynthetic capacity, reactive oxygen metabolism and ionic homeostasis in alkaline-treated cucumber plants were further investigated. Alkaline stress significantly caused ion imbalance, decreased photosynthetic pigment content, inhibited PSII activity and net photosynthetic rate. With prolonging stress time, electrolyte leakage, MDA and H2O2 contents were significantly increased in cucumber leaves, while antioxidative enzymes activity and ascorbate-glutathione cycle increased first and then decreased. Application of 75 μM SA reduced Na+ accumulation, maintained ionic homeostasis and normal operation of photosystem, enhanced the reactive oxygen species (ROS) scavenging system, reduced oxidative damage, and alleviated lipid peroxidation, thereby improved the alkaline-tolerance of cucumber plants.

Xanthine dehydrogenase (XDH) is a crucial enzyme involved in purine metabolism. Although the essential role of XDH is well studied in leguminous plants and Arabidopsis, the importance of this enzyme remains uncertain in rice. To evaluate how biochemistry indicators respond to XDH down-regulation and up-regulation in rice seedings during drought stress, RNA interference (RNAi) and CDS over-expression were used to generate transgenic lines of Nipponbare (Oryza sativa L.) in which OsXDH, the gene for XDH were silenced and over-expression. When the XDH-suppressed line was subjected to drought stress, the chlorophyll content and chlorophyll fluorescence parameters were markedly reduced in conjunction with significantly O 2 − enhanced production rate and MDA accumulation. This drought-hypersensitive biochemistry indicators was reversed in XDH-intensified line. Meanwhile, the XDH activity and its downstream metabolites were induced by drought stress. These observations support the notion that xanthine dehydrogenase was involved in regulating photosystem and reactive oxygen metabolism in drought stress in rice seedling.

We evaluated the effect of different light combinations on powdery mildew resistance and growth of melon seedlings. Light-emitting diodes were used as the light source and there were five light combinations: white light (420–680 nm); blue light (460 nm); red light (635 nm); RB31 (ratio of red and blue light, 3: 1); and RB71 (ratio of red and blue light, 7: 1). Compared with other treatments, blue light significantly decreased the incidence of powdery mildew in leaves of melon seedlings. Under blue light, H2O2 showed higher accumulation, and the content of phenolics, flavonoid and tannins, as well as expression of the genes involved in synthesis of these substances, significantly increased compared with other treatments before and after infection. Lignin content and expression of the genes related to its synthesis were also induced by blue light before infection. Melon irradiated with RB31 light showed the best growth parameters. Compared with white light, red light and RB71, RB31 showed higher accumulation of lignin and lower incidence of powdery mildew. We conclude that blue light increases melon resistance to powdery mildew, which is dependent on the induction of secondary metabolism that may be related to H2O2 accumulation before infection. Induction of tolerance of melon seeds to powdery mildew by RB31 is due to higher levels of sucrose metabolism and accumulation of lignin.

The light frequency of red (R) and blue (B) plays a crucial role within plant growth cycle. Whereas, the relationship between the metabolic pathways involved in photosynthesis and carbohydrate accumulation in tomato seedling and hormone regulation still needs further investigation. This research comprehensively analyzed changes in leaf anatomy, stomatal traits, pigment content, gas exchange parameters, chlorophyll fluorescence, Rubisco and Calvin cycle-related enzyme expression and activities, as well as endogenous hormones biosynthesis in tomato (Solanum lycopersicum L.) seedlings, which radiated by four light qualities, including monochromatic white light (W), B, R and mixed light of R and B (RB). The findings showed the biomass accumulation as well as CO2 assimilation were greatly increased in seedlings under B and especially under RB light. Their leaves were also thicker, and stomatal conductance, levels of pigment, photosynthetic electron transport capacity, and the photosynthetic rate were enhanced. In addition, enzyme expression level and activity related to the Calvin cycle were up-regulated. Moreover, RB-induced growth was accompanied by a significant inhibition in gibberellin (GA) concentration as well as an increment in auxin (indole-3-acetic acid (IAA)) in stem and root. Overall, photosynthesis of RB-treated seedlings was positively regulated by leaf anatomy and photosynthetic electron transportation as well as maintaining the activation states of the Calvin cycle, and then inducing changes in carbohydrate accumulation. In addition, both GA and IAA were found to be involved causally in the increased shoot and root biomass of tomato seedlings under RB treatment.

Low temperature (LT) and extreme humidity constantly threaten direct-seeded early indica rice production during the seedling stage. However, the physiological mechanism and damage induced by LT combined with high/low humidity are still unclear. A pot experiment was conducted to study seedling growth performance and physiological traits of two indica rice cultivars (i.e., the cold-sensitive cultivar Zhongjiazao17 and the cold-tolerant cultivar Xiangzaoxian6) under LT plus low humidity treatment (LL, 8°C; relative humidity, 25 %), LT plus high humidity treatment (LH, 8°C; relative humidity, 95 %) and a control treatment (CK, 25 °C; relative humidity, 75 %). The results showed that seedling height, rubisco concentration, and APX, PDH and α-KGDH activity significantly decreased under LL and LH compared to CK, and large decreases were found under LH, especially for the cold-sensitive cultivar Zhongjiazao17. However, LH significantly increased the reactive oxygen species O2− and the soluble protein, GSH and ABA concentrations. Moreover, the APX, PDH and α-KGDH activities, rubisco and chlorophyll concentrations, and GA3 induced by LH also significantly decreased after treatment. The differences in physiological traits of Zhongjiazao17 after LL and LH were significant. During three days of recovery, the physiological activity of the two cultivars under LL tended to recover to the level of CK, and the cold-tolerant cultivar showed reduced damage caused by humidity-cold combined stress. The results suggested that the double stress of low temperature plus high humidity rather than low temperature plus low humidity could decrease the growth performance by hampering photosynthetic and respiratory systems and altering the endogenous hormonal regulation of direct-seeded early indica rice, whereas it could significantly enhance the antioxidant protective system derived from the osmotic damage of leaves.

The ene reductases (ERs) from the old yellow enzymes (OYEs) family have the ability to reduce activated alkenes to generate up to two stereocenters, therefore they have been received extensive attention as powerful biocatalysts. In this study, through gene mining, four ERs were identified from the genomes of Ensifer adhaerens, Pseudomonas fluorescens, and Pseudomonas veronil. The biocatalytic properties of these four ERs were identified, and their applications in the synthesis process of dihydrocarvone and profen derivatives were further evaluated. Among them, three ERs (EaER2, PvER1, and PvER2) belonging to the classic OYEs showed the best catalytic activity at 30 °C and pH 7.0 (100 mM potassium phosphate buffer) and the PfER2, which belongs to the thermophilic-like OYEs exhibited the best catalytic at 40 °C and pH 7.0 (100 mM potassium phosphate buffer). When exploring the influence of organic solvents on the catalytic efficiency, it was found that the four ERs were more sensitive to toluene and had tolerance to several other selected organic solvents. In addition, EaER2, PfER2, PvER1 and PvER2 showed excellent catalytic activity toward carvone, and the stereoselectivity of PvER2 toward carvone could reach up to 88.7 % de. EaER2 and PfER2 can catalyze the synthesis of a variety of profen derivatives with a stereoselectivity over 99 % ee. Moreover, through homology modeling and molecular docking, we preliminarily explained the mechanism of catalytic activity and stereoselectivity of the four ERs, which provided a solid base on the rational design of their stereo-preference in the future. The discovery of EaER2, PfER2, PvER1, and PvER2 provides four new enzyme sources for the study of the OYEs family and enriches the biocatalytic toolbox of ERs. Our exploration of the enzymatic properties of these four ERs will provide the sufficient data basis for future research and industrialization progress.

Light qualities are thought to affect many plant physiological processes during growth and development. To investigate how light qualities influence tomato ( Solanum lycopersicum ) seedlings, the present study evaluated the effects of different light qualities generated by light emitting diodes (LEDs) with the same photosynthetic photon flux density (PPFD), including monochromic light red (657 nm, R), blue (457 nm, B), purple (417 nm, P) or white (W), combination of R and B lights (R:B = 1:1, 1R1B and R:B = 3:1, 3R1B) on the net photosynthetic rate (Pn), growth rate, carbohydrate content and sucrose-metabolizing enzyme activities. The results showed that relative to W, the seedling plant height and stem diameter were significantly promoted by combination of R and B lights and monochromic R light. However, the level of root growth was lower under R and P light, and the seedling growth and Pn were significantly suppressed under the latter. Additionally, R light significantly increased the contents of fructose and glucose, and combination of R and B lights significantly enhanced total carbohydrate, starch and sucrose accumulation, especially for 3R1B treatment. Activity of sucrose synthase (SS) was promoted under the different treatments and reached its highest value under 3R1B, which appeared to be a major contributor to the significantly higher content of starch under this treatment. Furthermore, R, B and P light reduced activity of sucrose phosphate synthase (SPS). Activities of acid invertase (AI) and neutral invertase (NI) were significantly increased by R light, but were markedly reduced under P. The results presented here indicated that monochromic R and combination lights 3R1B, could regulate the plant morphology and photosynthesis by the effects on the metabolism of carbohydrate into fructose, glucose, sucrose and starch, mainly through the enhanced activities of AI and NI under the former treatment, while SS and SPS in the latter treatment, respectively. They also improved the end-product output in tomato leaves, and may ultimately improve the yield and quality of tomato fruit.

Nitric oxide (NO) is a signal molecule that can mediate a wide range of physiological processes against cadmium (Cd) toxicity in plants. However, little information can be used to reveal the global and systematic mitigative mechanism of NO in improving Cd stress tolerance of cucumber plants. In the present study, we used Isobaric Tag for Relative and Absolute Quantification (iTRAQ) analysis to identify 1691 proteins, which can be used to determine the role of NO in regulating the molecular changes of proteome in cucumber leaves exposed to Cd stress. Several dysregulated key proteins indicated that Cd-induced physiological deterioration of cucumber leaves were mainly involved in metabolic process, cellular process, response to stimulus and so on. Metabolic pathway analysis indicated that several Cd-disruptive pathways were markedly reversed by NO treatments, including Cd transport and localization, photosynthesis, chlorophyll metabolism, redox homeostasis, glutathione-mediated Cd detoxification and Ca2+ signaling transduction. Taken together, this iTRAQ analysis provides more comprehensive insights into the physiological and molecular mechanisms of NO against Cd toxicity in cucumber plants.

Horseradish Peroxidase (HRP) was immobilized on copper surfaces with the linker of L-Cysteine (L-Cys) self-assembled films to form Cu/L-Cys/HRP electrodes. The activity of HRP can be preserved by the Cu/L-Cys self-assembled films. The Cu/L-Cys/HRP electrodes can be used for the selective electrocatalytic oxidase of p -dihydroxybenzen in absent of H 2 O 2 . The optimum pH for electrocatalyzing p -dihydroxybenzen was 5.5 or 7.0, which corresponds to the isoelectric points of L-Cys and HRP, respectively. X-ray photoelectron spectroscopy (XPS) provided the evidence that L-Cys linked with Cu surface by the Cu S bond. Fourier transform infrared spectroscopy (FTIR) analyses indicated that aromatic plane of p -dihydroxybenzen was connected parallel to porphyrin ring of heme in HRP. Quantum chemical calculation of density functional theory (DFT) revealed that symmetry of molecular structure and minimum space steric hindrance for p -dihydroxybenzen were benefit to combination with HRP. Moreover, the lowest energy of LUMO and most negative charges of oxygen atom on hydroxyl group of p -dihydroxybenzen were advantage to lose the hydrogen atom of hydroxyl group to be oxided.

Xanthine dehydrogenase (XDH) is an important enzyme in purine metabolism. It is involved in regulation of the normal growth and non-biological stress-induced ageing processes in plants. The present study investigated XDH’s role in regulating rice leaf senescence. We measured physical characteristics, chlorophyll content and fluorescence parameters, active oxygen metabolism, and purine metabolism in wild-type Kitaake rice (Oryza sativa L.), an OsXDH over-expression transgenic line (OE9), and an OsXDH RNA interference line (Ri3) during different growth stages. The expression patterns of the OsXDH gene confirmed that XDH was involved in the regulation of normal and abiotic stress-induced ageing processes in rice. There was no significant difference between the phenotypes of transgenic lines and wild type at the seedling stage, but differences were observed at the full heading and maturation stages. The OE9 plants were taller, with higher chlorophyll content, and their photosystems had stronger light energy absorption, transmission, dissipation, and distribution capacity, which ultimately improved the seed setting rate and 1000-seed weight. The opposite effect was found in the Ri3 plants. The OE9 line had a strong ability to remove reactive oxygen species, with increased accumulation of allantoin and alantoate. Experimental spraying of allantoin on leaves showed that it could alleviate chlorophyll degradation and decrease the content of H2O2 and malonaldehyde (MDA) in rice leaves after the full heading stage. The urate oxidase gene (UO) expression levels in the interference line were significantly lower than those in the over-expression line and wild-type lines. The allantoinase (ALN) and allantoate amidinohydrolase (AAH) genes had significantly higher expression in the Ri3 plants than the in OE9 or wild-type plants, with OE9 plants showing the lowest levels. The senescence-related genes ACD1, WRKY23, WRKY53, SGR, XERO1, and GH27 in Ri3 plants had the highest expression levels, followed by those in the wild-type plants, with OE9 plants showing the lowest levels. These results suggest that enhanced activity of XDH can regulate the synthesis of urea-related substances, improve plant antioxidant capacity, effectively delay the ageing process in rice leaves, and increase rice yield.

Lateral branches (LBs) pruning is performed frequently to keep the tomato plants in optimal growth conditions. However, the suitable pruning length of LBs, as well as it-mediated physiological and molecular mechanisms on plant growth regulation remains elusive in tomato. The effects of pruning length of LBs from 0 to 20 cm on vegetative growth, reproductive growth, labor costs, hormone metabolism and genes transcripts were evaluated on indeterminate type tomato cultivar. By comprehensive analysis, we provided evidence that pruning length of LBs at about 6 ~ 7 cm was suitable for plant growth, high yield, and low labor costs in tomato production. For mechanisms, appropriate extension of pruning length of LBs increased indole acetic acid (IAA) concentrations in root, which promoted the biosynthesis and upward transport of inactive cytokinins (CKs), as well as root development. Meanwhile, existence of LBs had inhibited effect on auxin outflow of the lower fruit stalks by testing transcripts of AUX1 and PIN , which increased the IAA and CKs concentrations of ovary and then promoted fruit setting and swelling. Additionally, pruning length of LBs also influenced the leaf senescence to control assimilation. Taken together, we highlighted that pruning length of LBs influenced auxin and cytokinins homeostasis in relation to growth and yields in tomato plants.

5’-hydroxymethylcytosine (5hmC), an important 5’-cytosine modification, is altered highly in order in male meiotic prophase. However, the regulatory mechanism of this dynamic change and the function of 5hmC in meiosis remain largely unknown. Using a knockout mouse model, we showed that UHRF1 regulated male meiosis. UHRF1 deficiency led to failure of meiosis and male infertility. Mechanistically, the deficiency of UHRF1 altered significantly the meiotic gene profile of spermatocytes. Uhrf1 knockout induced an increase of the global 5hmC level. The enrichment of hyper-5hmC at transcriptional start sites (TSSs) was highly associated with gene downregulation. In addition, the elevated level of the TET1 enzyme might have contributed to the higher 5hmC level in the Uhrf1 knockout spermatocytes. Finally, we reported Uhrf1, a key gene in male meiosis, repressed hyper-5hmC by downregulating TET1. Furthermore, UHRF1 facilitated RNA polymerase II (RNA-pol2) loading to promote gene transcription. Thus our study demonstrated a potential regulatory mechanism of 5hmC dynamic change and its involvement in epigenetic regulation in male meiosis.

S-nitrosylation, regulated by S-nitrosoglutathione reductase (GSNOR), is considered as an important route for nitric oxide (NO)-modulated stress tolerance in plants. However, genetic evidence for the GSNOR-mediated integrated regulation of S-nitrosylation and plant stress response remains elusive until now. In the present study, we used a site-specific nitrosoproteomic approach to identify 334 endogenously S-nitrosylated proteins with 425 S-nitrosylated sites from the wild type (WT) and GSNOR-knockdown (G) tomato plants under both control (C) and sodic alkaline stress (S) conditions. In detail, the results revealed 68, 92, 54 and 56 up-regulated, as well as 10, 36, 14 and 10 down-regulated S-nitrosylated proteins in G-C/WT-C, G-S/WT-S, WT-S/WT-C, and G-S/G-C, which is the first dataset for S-nitrosylated proteins in Solanaceae. These S-nitrosylated proteins are involved in a wide range of various metabolic, cellular and catalytic processes. Based on this data, proteins involving in NO homeostasis control, signaling of Ca2+, ethylene and MAPK, reactive oxygen species (ROS) scavenging, osmotic regulation, as well as energy support pathway have been identified and selected as the key and sensitive targets that were regulated by GSNOR-modulated S-nitrosylation in response to sodic alkaline stress. Taken together, GSNOR is actively involved in the regulation of sodic alkaline stress tolerance by S-nitrosylation. And the present study provided valuable resources and new clues for the study of S-nitrosylation-regulated metabolism in tomato plants.

With regard to plant growth and development, red (R) and blue (B) light are essential light qualities. Moreover, it has been previously reported that melatonin has an effect dominates regulating fruit ripening. Nevertheless, people know little about the specific mechanism by which R and B light regulate melatonin levels and fruit ripening in tomato (Solanum lycopersicum L.). In this research, the effect of R and B light on changes in endogenous melatonin levels and fruit quality during tomato ripening involved monochromatic light of white (W, control), R, B and mixed R and B (RB) light was investigated. According to the findings, melatonin decreased with the fruit ripening, which was accompanied by enhanced levels of fruit softening, ethylene biosynthesis, respiration rate and lycopene accumulation, as well as the conversion of carbohydrates. Furthermore, compared to monochromatic R and B light, RB light noticeably enhanced the melatonin content in tomato fruit, which promoted the ripening of tomato fruit consequently and led to accelerated fruit softening as well as upregulation of ethylene and lycopene biosynthesis, respiration rate, antioxidant activity and carbohydrate accumulation. It is concluded that RB light may regulate endogenous melatonin, thus promoting fruit ripening and quality improvement of tomato through cross-talk with other biomolecules, by increased ethylene production and signaling.

Cotyledon senescence is an important problem in industrialized seedling production. The effects of cold plasma (CP) treatments with different power levels from 0 to 100 W on the cotyledon chlorosis ratio and abscission ratio of tomato (Solanum lycopersicum L.) seedlings were investigated under normal conditions. CP treatment with 25 W resulted in the lowest ratios of chlorosis and abscission, which significantly inhibited cotyledon senescence. Further study of dark-induced cotyledon senescence indicated that 25 W CP treatment inhibited chlorophyll breakdown, the loss of photosystem II function, and the transcription of senescence-related genes SAG12 and ORE1 during darkness. Transcripts of RBOH1, MAPK1/2 and hydrogen peroxide (H2O2) concentrations were induced by CP treatment under normal conditions and early periods of darkness. However, both antioxidant enzymes and ascorbate-glutathione cycle were activated by CP treatment in late periods of darkness. In addition, the levels of three kinds of cytokinins (CKs) were enhanced, and ethylene concentrations were inhibited by CP treatment during darkness. Taken together, these physiological changes, which were caused by CP treatment, led to a senescence-delayed phenotype of tomato cotyledons. The present study provides a novel CP treatment approach for delaying cotyledon senescence in tomato seedlings, which is an easy, effective, and industrial technology that can significantly improve tomato seedling quality.

Exonuclease 5 (Exo5) belongs to a class of bi-directional, ssDNA-specific exonucleases that mainly involved in the DNA repair pathways. Exo5 has been reported to be crucial for DNA- DNA mismatch repair (MMR) in several human cell lines. However, its in vivo function in mammals still needs to be explored. Thus, to study the in vivo role of Exo5 in spermatogenesis, Exo5 knockout mice were generated using CRISPR/Cas9 technology. Unexpectedly, we found that the knockout mice are fertile despite a slight decrease in sperm count. Furthermore, Exo5-/- mice showed no detectable developmental anomalies, exhibited no remarkable differences in the epididymal histology and testis/body weight ratio. Moreover, cytological investigations on meiocytes revealed non-significant differences in chromosomal synapsis, recombination, and meiotic progression of prophase I, further demonstrating that Exo5 has no essential role in spermatogenesis in mice under normal breeding conditions. Collectively, these data indicate that Exo5 is dispensable for meiotic progression and fertility in mice.

Meiosis is an essential step in gametogenesis which is the key process in sexually reproducing organisms as meiotic aberrations may result in infertility. In meiosis, programmed DNA double-strand break (DSB) formation is one of the fundamental processes that are essential for maintaining homolog interactions and correcting segregation of chromosomes. Although the number and distribution of meiotic DSBs are tightly regulated, still abnormalities in DSB formation are known to cause meiotic arrest and infertility. This review is a detailed account of molecular bases of meiotic DSB formation, its evolutionary conservation, and variations in different species. We further reviewed the mutations of DSB formation genes in association with human infertility and also proposed the future directions and strategies about the study of meiotic DSB formation.

China is the world’s largest emitter of gaseous ammonia (NH 3 ), a compound carrying severe human health and ecosystem risks. Fertilizer N application is a major source of this atmospheric NH 3 . Although many studies have measured NH 3 emissions from croplands in China, the effect of fertilizer management on yield-scaled NH 3 emissions (i.e., NH 3 intensity defined as NH 3 emissions per unit crop yield) is not so clear. Thus, we performed a meta-analysis to quantify the effect of fertilizer management on NH 3 emissions and NH 3 intensity in China’s croplands. Results showed that the increases in NH 3 emissions and NH 3 intensity over a control were greater at high N rates (averaging 305 kg N ha −1 ) than at low and moderate N rates (average of 130 and 206 kg N ha −1 , respectively), while crop yields stayed flat over this range. Rice had greater increases in NH 3 emissions and NH 3 intensity in response to inorganic N addition than other crops. The emission factor for NH 3 was also higher for rice than other crops, and increased with increasing proportions of basal N and soil organic carbon and total N content. Relative to surface application, deep placement of fertilizer N significantly decreased NH 3 emissions and NH 3 intensity. Increasing the number of split applications of fertilizer N significantly reduced NH 3 emissions and NH 3 intensity. Organic manure amendments substituting for all or part of inorganic fertilizer N significantly mitigated NH 3 emissions and led to a reduction in NH 3 intensity but without statistical significance. The use of slow release fertilizers (SR) and urease inhibitors (UI) significantly reduced NH 3 emissions and NH 3 intensity, whereas application of nitrification inhibitors actually increased both. Overall, this meta-analysis demonstrates that appropriate fertilizer management practices such as reducing inorganic N rates, deep placement and split applications of fertilizer N, and using SR and UI can all reduce NH 3 emissions and NH 3 intensity in China’s croplands.

A hydroponic study was conducted to determine the effects of selenium (Se: 0, 3, 6 μmol L –1 ) on senescence-related oxidative stress in garlic plants grown under two sulfur (S) levels. We evaluated the yields of plants harvested at 160 and 200 days after sowing. Plants grown under a low Se dose (0.3 μmol L –1 ) at low S level showed higher yields (12.0% increase in fresh weight yield, 13.7% increase in dry weight yield) than the controls, despite a decrease in chlorophyll concentration. Compared with control plants, the Se-treated plants showed lower levels of lipid peroxidation. The Se-treated plants also showed higher activities of glutathione peroxidase and catalase, but lower superoxide dismutase activities. Changes in F v / F m values and proline contents were affected more strongly by S than by Se. On the basis of our results, we can conclude that Se plays a key role in the antioxidant systems in garlic seedlings. It delays senescence by alleviating the peroxide stress, but it can be toxic at high levels. A high S level may increase tolerance to high Se concentrations through reducing Se accumulation in plants.

High-efficiency deep blue organometallic phosphors are imperative to organic luminescence devices. While green iridium complexes commonly exhibit high luminescence efficiencies, the luminescence quantum efficiency always drops sharply when emission becomes deep blue. In this work, the microscopic mechanism of such a drastic decrease is elucidated from detailed computational investigation. Both radiative (kr) and non-radiative (knr) decay rates of the lowest triplet state (T1) are calculated for five representative cyclometalated iridium(III) complexes with emission color ranging from green to deep blue, based on phenylpyridyl, phenylpyrazolyl, bipyridinato, pyrimidinpyridyl, and pyrimidinprazolyl ligands. For all compounds, the T1 states are characteristic of mixed intraligand (π → π*) transition and iridium-to-ligand charge transfer (d → π*), and the increased π → π* and decreased d → π* portions lead to the blue-shifted emission of 1 < 2 < 4 < 5 < 3. Strikingly, it is found that the drastic increase of knr arising from severe intra-ligand vibration relaxations induced by the enhanced π → π* transition is mainly responsible for the droop of the phosphorescence quantum efficiency, which provides a different deactivation mechanism from the thermally-activated transformation into a dark metal-centred ligand field excited state reported in many previous studies. Compared with the well-studied compounds 1–3, the newly designed compounds 4 and 5 achieve a good balance between high efficiency and a large energy gap and are very promising as deep blue phosphors. These findings are expected to be helpful for the rational design of high-efficiency blue organometallic phosphors, especially in terms of ligands.

Caffeic acid O-methyltransferase (COMT) controls the biosynthesis of lignin and melatonin. Though melatonin-induced stress tolerance has been widely studied, little can be found about COMT1-mediated low phosphorus (LP) stress tolerance and metabolic characteristic. Transgenic plants overexpressing COMT1 (COMT1) exhibited a significant increase in tolerance to LP stress by promoting plant growth and P uptake compared with wild type (WT) plants. Then, a LC MS based approach was used to conduct a detailed broad-scale identification of metabolic responses of WT and COMT1 tomato roots to LP stress. Totally, 5918 metabolites were identified in the present study, which contained 480–551 significantly changed metabolites (SCMs) in four comparative groups. PCA analysis of these SCMs strongly showed a COMT1-mediated LP resistance process at metabolic level. These SCMs were enriched in 11 shared pathways in comparative groups of “LP effect” and “COMT1 effect”. We further condensed these pathways to five parts: citrate cycle, amino acids biosynthesis and metabolism, arginine-mediated nitric oxide and polyamine metabolism, linoleic acids metabolism, organic acids and derivatives metabolism. A detailed discussion around these five metabolic parts was conducted to unravel tomato LP response and COMT1-mediated resistance mechanism. Taken together, this metabolomics analysis provided more global insights into the physiological and molecular mechanisms of COMT1 against LP stress in tomato plants at metabolic levels.

Environmental stresses, like drought and salt, seriously threaten the productivity of tomato (Solanum lycopersicum L.). S-adenosylmethionine synthetase (SAMS) is responsible for synthesis of SAM that plays important roles in regulating plant-environment interactions. In this study, we analyzed the function of tomato SAMS1 (SlSAMS1) gene under drought and salt stresses. Promoter analysis showed that the promoter region of SlSAMS1 had several stress-related cis-regulatory elements. Expression pattern analysis indicated that SlSAMS1 was induced by salt, drought, low temperature and abscisic acid (ABA) treatments. Overexpression of SlSAMS1 in tomato improved drought and salt stresses tolerance. Under drought and salt stresses, water-retention capacity and photosynthetic capacity were significantly enhanced in transgentc lines. In addition, overexpression of SlSAMS1 significantly reduced the accumulation of superoxide, hydrogen peroxide (H2O2) and malondialdehyde, and enhanced ABA content and reactive oxygen species scavenging enzymes (superoxide dismutase, catalase and ascorbate peroxidase) activities. Furthermore, drought and salt treatment enlarged the influences caused by overexpressing SlSAMS1 in polyamines (PAs) synthesis and ethylene emission. Interestingly, water loss assay indicated that SlSAMS1 modulated the generation of PAs and H2O2, not ethylene, to maintain a better water homeostasis in transgenic plants. Moreover, ABA induced the expression of PAs and ethylene synthesis related genes to change PAs contents and ethylene emission. Importantly, compared with wild type plants, transgenic plants reduced water loss under ABA treatment. Collectively, these results suggested that SlSAMS1 involved in tomato drought and salt tolerance mainly through mediated PAs, H2O2 and ABA signals.

Tomato (Solanum lycopersicum L.) fruits undergo major metabolic changes in ripening stage. Many studies indicated that exogenous application of moderate salt during fruit ripening could improve tomato fruit quality. In addition, protein N-glycosylation played an important role in respond to salt stress and regulated fruit ripening. However, there is no reports about the link between N-glycosylation, salt stress and fruit quality. In this study, through GC–MS analysis, we measured the contents of 13 sugars metabolites and 10 sugars metabolites were significantly changed in salt treated tomato red rip fruits compared with the control red rip fruits. Then, using N-glycoproteome analysis, we identified 442 N-glycosites from 310 N-glycoproteins in comparison of salt-treated red ripe fruits and the control red ripe fruits. Interestingly, salt treatment dramatically triggered the down-regulation of N-glycosites, suggesting protein N-glycosylation reprogramming under salt condition. Following statistical analysis, the N-glycosylation levels of many proteins related to sugar conversion, taste-modifying and fruit firmness were significantly changed under salt treatment. Collectively, the data provides the link between N-glycosylation, salt stress and fruit quality for the first time. In addition, this study also contributed to understanding the effect of environmental changes on post-translational modification mediated fruit quality.

Proteomics and metabolomics were used to study the changes in proteins and metabolites in tomato fruits at different ripening stages and the effect of salt treatment on fruit quality. The results showed 2607 and 153 differentially expressed proteins in ripe fruits compared with mature green fruits and in NaCl-treated ripe fruits compared with control ripe fruits, respectively. KEGG analysis indicated that these proteins were mainly involved in photosynthesis, pentose and glucuronate interconversions in different ripening stages of fruits, and salt-induced proteins were involved in flavonoid biosynthesis and linoleic acid metabolism. A series of metabolites, including carbohydrates and amino acids showed significantly different accumulations between ripe and mature green fruits and between salt-treated and control fruits. Combined analysis explored glycine, L-alanine, D-xylose and sucrose and some proteins involved in multiple metabolic pathways under salt conditions. Their interactions might affect fruit development and fruit quality under salt treatment.

Protein N-glycosylation plays key roles in protein folding, stability, solubility, biogenesis, and enzyme activity. Tomato (Solanum lycopersicum L.) is an important vegetable crop with abundant nutritional value, and the formation of tomato fruit qualities primarily occurs in the fruit ripening process. However, a large number of N-glycosylation-mediated mechanisms in regulating tomato fruit ripening have not been elucidated to date. In this study, western blot assays showed that the extents of mature N-glycoproteins were differentially expressed in mature green fruits (fruit start ripening) and ripe fruits (fruit stop ripening). Next, through performing a comparative N-glycoproteome analysis strategy, a total of 553 N-glycosites from 363 N-glycoproteins were identified in mature green fruits compared with ripe fruits. Among them, 252 N-glycosites from 191 N-glycoproteins were differentially expressed in mature green fruits compared with ripe fruits. The differentially expressed N-glycoproteins were mainly located in the chloroplast (30 %) and cytoplasm (16 %). Gene Ontology (GO) analysis showed that these N-glycoproteins were involved in various biological processes, cellular components and molecular functions. These N-glycoproteins participate in biological processes, such as metabolic processes, cellular processes and single-organism processes. These N-glycoproteins are also cellular components in biological process cells, membranes and organelles and have different molecular functions, such as catalytic activity and binding. Notably, these N-glycoproteins were enriched in starch and sucrose metabolism and galactose metabolism by KEGG pathway analysis. This community resource regarding N-glycoproteins is the first large-scale N-glycoproteome during plant fruit ripening. This study will contribute to understanding the function of N-glycosylation in regulating plant fruit ripening.

To evaluate the actual response of rice starch physicochemical properties to climate warming, a field warming experiment was conducted with four indica rice cultivars using free-air temperature increase (FATI) facility in a double rice cropping system. FATI facility increased rice canopy temperature by 1.4–2.1 °C during the entire growth period. The responses of starch physicochemical properties to experimental warming were basically consistent for both early and late rice. On average, experimental warming increased the starch relative crystallinity, granule average diameter, and amylopectin average chain length by 14.3%, 6.9%, and 2.4%, respectively. These resulted in starch with lower swelling power, water solubility, and pasting viscosity, but higher gelatinization temperatures and gelatinization enthalpy. Our study indicated that experimental warming affected the rice starch physicochemical properties, and would provide some useful information on how to guide the rice starch end use in food and non-food industries under climate warming.

Salinity threatens the productivity of tomato (Solanum lycopersicum L.). R2R3-type MYB transcription factors are important regulators in response to environmental stress. Here, we analyzed the function of the tomato R2R3-type MYB gene SlMYB102. A transcriptional activation assay showed that SlMYB102 had transactivation activity in yeast. Promoter analysis showed that multiple stress-related elements were found in the promoter of SlMYB102. Furthermore, SlMYB102 was induced by osmotic stress, particularly by salt stress. The overexpression of SlMYB102 in tomato affected multiple parameters under salinity stress. Under long-term salt stress, the degree of growth inhibition was significantly reduced in the two overexpression (OE) lines. In addition, the two OE lines maintained a better K+/Na+ ratio, lower reactive oxygen species (ROS) generation (O2•- production rate and H2O2 content) and lower electrolytic leakage rates than the wild type (WT). The activity of ROS scavenging enzymes including superoxide dismutase, peroxidase, catalase and ascorbate peroxidase, and the accumulation of antioxidants (ascorbic acid and glutathione) and proline was higher in the two OE lines compared with WT. The qRT-PCR analysis confirmed that the transcript abundance of many salt stress-related genes (SlSOS1, SlSOS2, SlNHX3, SlNHX4, SlHAK5, SlCPK1 and SlCPK3) was upregulated in two OE lines under salt stress. Collectively, these results suggest that SlMYB102 participates in tomato tolerance through the regulation of a series of molecular and physiological processes.

Iron (Fe) is an essential micronutrient element for plant growth. The S-nitrosoglutathione reductase (GSNOR) gene's functions under Fe-deficiency conditions are not well understood. Here, GSNOR expression was induced by Fe deficiency in tomato (Solanum lycopersicum L.) leaves and roots, while its overexpression alleviated chlorosis under Fe-deficiency conditions. GSNOR overexpression positively regulated the Fe distribution from root to shoot, which might result from the transcriptional regulation of genes involved in Fe metabolism. Additionally, the overexpression of GSNOR maintained redox homeostasis and protected chloroplasts from Fe-deficiency-related damage, resulting in a greater photosynthetic capacity. As a nitric oxide regulator, GSNOR's overexpression decreased the excessive accumulation of nitric oxide and S-nitrosothiols during the Fe deficiency, and maintained the homeostases of reactive oxygen species and reactive nitrogen species. Moreover, GSNOR overexpression, probably at the level of genes and proteins, along with protein S-nitrosylation, promoted Fe uptake and regulated the shoot/root Fe ratio under Fe-deficiency conditions.