Multi-Omics Analyses of Lettuce (Lactuca sativa) Reveals Primary Metabolism Reorganization Supporting Distinct Features of Secondary Metabolism Induced by Supplementing UV-A Radiation.

UV can serve as an effective light spectrum for regulating plant secondary metabolites, while relevant studies on UV-A are much less extensive than those on UV-B. A comprehensive understanding of the selective effects of UV-A on different secondary metabolites and the specific features of primary metabolism that drive these effects is still lacking. To address this knowledge gap, we conducted a study to analyze the dynamic changes in the metabolome and transcriptome of lettuce leaves irradiated with red plus UV-A light (monochromatic red light as control). Generally, UV-A promoted the synthesis of most phenylpropanoids and terpenoids originating from the shikimate and methylerythritol phosphate (MEP) pathway in plastids but sacrificed the synthesis of terpenoids derived from the mevalonate (MVA) pathway, particularly sesquiterpenes. Increased precursors supply for the shikimate and MEP pathway under UV-A was directly supported by the activation of the Calvin-Benson cycle and phosphoenolpyruvate transport. Whereas, along with phosphoenolpyruvate transport, the TCA cycle was restrained, causing deprivation of the MVA pathway precursor. In addition, UV-A also activated the plastidic oxidative branch of the pentose phosphate pathway, photorespiration, and malate shuttle, to ensure a sufficient supply of nitrogen, circulation homeostasis of the Calvin-Benson cycle, and energy balance, thus indirectly supporting UV-A-induced specific secondary metabolic output. This study provides a comprehensive framework for understanding the flexible primary-secondary metabolism interactions that are able to produce specific metabolites favorable for adaptation to environmental stimuli.

Integrated transcriptomic and metabolomic analysis provides insights into cold tolerance in lettuce (Lactuca sativa L.).

The popular leafy vegetable lettuce (Lactuca sativa L.) is susceptible to cold stress during the growing season, which slows growth rate, causes leaf yellowing and necrosis, and reduced yield and quality. In this study, transcriptomic and metabolomic analyses of two cold-resistant lettuce cultivars (GWAS-W42 and F11) and two cold-sensitive lettuce cultivars (S13K079 and S15K058) were performed to identify the mechanisms involved in the cold response of lettuce. Overall, transcriptome analysis identified 605 differentially expressed genes (DEGs), including significant enrichment of genes involved in the flavonoid and flavonol (CHS, CHI, F3H, FLS, CYP75B1, HCT, etc.) biosynthetic pathways related to oxidation-reduction and catalytic activity. Untargeted metabolomic analysis identified fifteen flavonoid metabolites and 28 other metabolites potentially involved in the response to cold stress; genistein, quercitrin, quercetin derivatives, kaempferol derivatives, luteolin derivatives, apigenin and their derivatives accumulate at higher levels in cold-resistant cultivars. Moreover, MYBs, bHLHs, WRKYs and Dofs also play positive role in the low temperature response, which affected the expression of structural genes contributing to the variation of metabolites between the resistant and sensitive. These results provide valuable evidence that the metabolites and genes involved in the flavonoid biosynthetic pathway play important roles in the response of lettuce to cold stress.

Novel Bismuth Nanoflowers Encapsulated in N-Doped Carbon Frameworks as Superb Composite Anodes for High-Performance Sodium-Ion Batteries.

Bismuth (Bi) has attracted attention as a promising anode for sodium-ion batteries (SIBs) owing to its suitable potential and high theoretical capacity. However, the large volumetric changes during cycling leads to severe degradation of electrochemical performance and limits its practical application. Herein, Bi nanoflowers are encapsulated in N-doped carbon frameworks to construct a novel Bi@NC composite via a facile solvothermal method and carbonization strategy. The well-designed composite structure endows the Bi@NC with uniformly dispersed Bi nanoflowers to alleviate the attenuation while the N-doped carbon frameworks improve the conductivity and ion transport of the whole electrode. As for sodium-ion half-cell, the electrode exhibits a high specific capacity (384.8 mAh g-1 at 0.1 A g-1 ) and excellent rate performance (341.5 mAh g-1 at 10 A g-1 ), and the capacity retention rate still remains at 94.9% after 5000 cycles at 10 A g-1 . Furthermore, the assembled full-cell with Na3 V2 (PO4 )3 cathode and Bi@NC anode can deliver a high capacity of 251.5 mAh g-1 at 0.1 A g-1 , and its capacity attenuates only 0.009% in each cycle after 2000 times at 5.0 A g-1 . This work offers a convenient, low-cost, and eco-friendliness approach for high-performance electrodes in the field of sodium ion electrochemical storage technology.

Estimating the frost damage index in lettuce using UAV-based RGB and multispectral images.

Introduction: The cold stress is one of the most important factors for affecting production throughout year, so effectively evaluating frost damage is great significant to the determination of the frost tolerance in lettuce. Methods: We proposed a high-throughput method to estimate lettuce FDI based on remote sensing. Red-Green-Blue (RGB) and multispectral images of open-field lettuce suffered from frost damage were captured by Unmanned Aerial Vehicle platform. Pearson correlation analysis was employed to select FDI-sensitive features from RGB and multispectral images. Then the models were established for different FDI-sensitive features based on sensor types and different groups according to lettuce colors using multiple linear regression, support vector machine and neural network algorithms, respectively. Results and discussion: Digital number of blue and red channels, spectral reflectance at blue, red and near-infrared bands as well as six vegetation indexes (VIs) were found to be significantly related to the FDI of all lettuce groups. The high sensitivity of four modified VIs to frost damage of all lettuce groups was confirmed. The average accuracy of models were improved by 3% to 14% through a combination of multisource features. Color of lettuce had a certain impact on the monitoring of frost damage by FDI prediction models, because the accuracy of models based on green lettuce group were generally higher. The MULTISURCE-GREEN-NN model with R2 of 0.715 and RMSE of 0.014 had the best performance, providing a high-throughput and efficient technical tool for frost damage investigation which will assist the identification of cold-resistant green lettuce germplasm and related breeding.

Biodegradation of polybutylene adipate-co-terephthalate by Priestia megaterium, Pseudomonas mendocina, and Pseudomonas pseudoalcaligenes following incubation in the soil.

Soil that contained polybutylene adipate-co-terephthalate (PBAT) was incubated with Priestia megaterium, Pseudomonas mendocina, and Pseudomonas pseudoalcaligenes to improve the biodegradative process of this polymer. The mixture of Pr. megaterium and Ps. mendocina was highly effective at biodegrading the PBAT, and after eight weeks of soil incubation, approximately 84% of the PBAT film weight was lost. Mixtures of the other two species also positively affected the synergistic degradation of PBAT film in the soil, but the mixture of three species had a negative effect. The residual PBAT film microstructure clearly demonstrated the degradation of PBAT, and the degree of degradation was related to the different species. Cleavage of the PBAT film ester bond after soil microbial action affected its properties. The incubation of PBAT in soil that contained these species affected soil dehydrogenase and soil lipase in particular. The secretion of lipase by these species could play an important role in the degradation of PBAT in the soil.

P450s mediated enhanced herbicide metabolism involved in the thifensulfuron-methyl resistance in Ipomoea purpurea L.

Ipomea purpurea (L.) Roth. reduces dry land crop yield and quality in Northeast China, especially in Liaoning Province. Frequent use of thifensulfuron-methyl in recent years has resulted in herbicide resistance in I. purpurea. We evaluated resistance levels of I. purpurea to thifensulfuron-methyl, an acetolactate synthase (ALS) inhibitor, in Liaoning Province and further investigated the resistance mechanisms. The results showed that 15 populations of I. purpurea have evolved up to 5.81-34.44-fold resistance to thifensulfuron-methyl, compared to the susceptible population (S), among which LN3 was the most resistant. DNA sequencing of the ALS gene in susceptible and resistant populations did not reveal any target site mutations that could be associated with resistance to thifensulfuron-methyl in I. purpurea. Additionally, no significant difference was detected between the in vitro ALS activity of LN3 and S. The GR50 of LN3 decreased sharply by 47% when malathion (a P450 inhibitor) was applied with thifensulfuron-methyl. Absorption of thifensulfuron-methyl by LN3 was equal to that of S; however, LN3 metabolized the herbicide significantly faster. This was repressed after the inhibition of P450s activity. Collectively, our results confirmed that I. purpurea in Liaoning Province has developed resistance to thifensulfuron-methyl and implied that the resistance was conferred by the increase in detoxification mediated by P450s. Furthermore, LN3 was sensitive to fluroxypyr, which can be used as an alternative to control I. purpurea.

Differential Metabolic Responses of Lettuce Grown in Soil, Substrate and Hydroponic Cultivation Systems under NH4+/NO3- Application.

Nitrogen (N) is an essential element for plant growth and development. The application of a balanced and optimal amount of N is required for sustainable plant yield. For this, different N sources and forms are used, that including ammonium (NH4+) and nitrate (NO3-). These are the main sources for N uptake by plants where NH4+/NO3- ratios have a significant effect on the biomass, quality and metabolites composition of lettuce grown in soil, substrate and hydroponic cultivation systems. A limited supply of N resulted in the reduction in the biomass, quality and overall yield of lettuce. Additionally, different types of metabolites were produced with varying concentrations of N sources and can be used as metabolic markers to improve the N use efficiency. To investigate the differential metabolic activity, we planted lettuce with different NH4+/NO3- ratios (100:0, 75:25, 50:50, 25:75 and 0:100%) and a control (no additional N applied) in soil, substrate and hydroponic cultivation systems. The results revealed that the 25% NH4+/75% NO3- ratio increased the relative chlorophyll contents as well as the biomass of lettuce in all cultivation systems. However, lettuce grown in the hydroponic cultivation system showed the best results. The concentration of essential amino acids including alanine, valine, leucine, lysine, proline and serine increased in soil and hydroponically grown lettuce treated with the 25% NH4+/75% NO3- ratio. The taste and quality-related compounds in lettuce showed maximum relative abundance with the 25% NH4+/75% NO3- ratio, except ascorbate (grown in soil) and lactupicrin (grown in substrate), which showed maximum relative abundance in the 50% NH4+/50% NO3- ratio and control treatments, respectively. Moreover, 1-O-caffeoylglucose, 1,3-dicaffeoylquinic acid, aesculetin and quercetin-3-galactoside were increased by the application of the 100% NH4+/0% NO3- ratio in soil-grown lettuce. The 25% NH4+/75% NO3- ratio was more suitable in the hydroponic cultivation system to obtain increased lettuce biomass. The metabolic profiling of lettuce showed different behaviors when applying different NH4+/NO3- ratios. Therefore, the majority of the parameters were largely influenced by the 25% NH4+/75% NO3- ratio, which resulted in the hyper-accumulation of health-promoting compounds in lettuce. In conclusion, the optimal N applications improve the quality of lettuce grown in soil, substrate and hydroponic cultivation systems which ultimately boost the nutritional value of lettuce.

Surface Properties, Free Volume, and Performance for Thin-Film Composite Pervaporation Membranes Fabricated through Interfacial Polymerization Involving Different Organic Solvents.

The type of organic solvents used in interfacial polymerization affects the surface property, free volume, and separation performance of the thin-film composite (TFC) polyamide membrane. In this study, TFC polyamide membrane was fabricated through interfacial polymerization between diethylenetriamine (DETA) and trimesoyl chloride (TMC). Four types of organic solvent were explored in the preparation of pervaporation membrane. These are tetralin, toluene, hexane, and isopentane. The solubility parameter distance between organic solvents and DETA follows in increasing order: tetralin (17.07 MPa1/2) < toluene (17.31 MPa1/2) < hexane (19.86 MPa1/2) < isopentane (20.43 MPa1/2). Same trend was also observed between the organic solvents and DETA. The larger the solubility parameter distance, the denser and thicker the polyamide. Consequently, field emission scanning electron microscope (FESEM) and positron annihilation spectroscopy (PAS) analysis revealed that TFCisopentane had the thickest polyamide layer. It also delivered the highest pervaporation efficiency (permeation flux = 860 ± 71 g m-2 h-1; water concentration in permeate = 99.2 ± 0.8 wt%; pervaporation separation index = 959,760) at dehydration of 90 wt% aqueous ethanol solution. Furthermore, TFCisopentane also exhibited a high separation efficiency in isopropanol and tert-butanol. Therefore, a suitable organic solvent in preparation of TFC membrane through interfacial polymerization enables high pervaporation efficiency.

Supportive role of the Na+ transporter CmHKT1;1 from Cucumis melo in transgenic Arabidopsis salt tolerance through improved K+/Na+ balance.

KEY MESSAGE: CmHKT1;1 selectively exports Na+ from plant cells. Upon NaCl stress, its expression increased in a salt-tolerant melon cultivar. Overexpression of CmHKT1;1 increased transgenic Arabidopsis salt tolerance through improved K+/Na+ balance. High-affinity K+ transporters (HKTs) are thought to be involved in reducing Na+ in plant shoots under salt stress and modulating salt tolerance, but their function in a moderately salt-tolerant species of melon (Cucumis melo L.) remains unclear. In this study, a Na+ transporter gene, CmHKT1;1 (GenBank accession number: MK986658), was isolated from melons based on genome data. The transcript of CmHKT1;1 was relatively more abundant in roots than in stems or leaves from melon seedlings. The tobacco transient expression system showed that CmHKT1;1 was plasma-membrane localized. Upon salt stress, CmHKT1;1 expression was more strongly upregulated in a salt-tolerant melon cultivar, 'Bingxuecui' (BXC) compared with a salt-sensitive cultivar, 'Yulu' (YL). Electrophysiological evidence demonstrated that CmHKT1;1 only transported Na+, rather than K+, when expressed in Xenopus laevis oocytes. Overexpression of CmHKT1;1 increased salt sensitivity in Saccharomyces cerevisiae and salt tolerance in Arabidopsis thaliana. Under NaCl treatments, transgenic Arabidopsis plants accumulated significantly lower concentrations of Na+ in shoots than wild type plants and showed a better K+/Na+ balance, leading to better Fv/Fm, root length, biomass, and enhanced plant growth. The CmHKT1;1 gene may serve as a useful candidate for improving crop salt tolerance.

Self-Supported 3 D Ultrathin Cobalt-Nickel-Boron Nanoflakes as an Efficient Electrocatalyst for the Oxygen Evolution Reaction.

The development of highly active and efficient nonprecious-metal electrocatalysts for the oxygen evolution reaction is important for the design of renewable energy production and storage devices. In this work, highly dense, ultrathin Co-Ni boride nanoflakes supported on a 3 D CoNi skeleton are fabricated in situ by a simple one-step, high-temperature, solid-state boronation process. As a result of the induced high electroactive surface area and low charge transfer resistance, CoNiB-700 exhibits high catalytic activity at an overpotential of 262 (η10 ) and 284 mV (η20 ) to deliver current densities of 10 and 20 mA cm-2 , respectively, with a Tafel slope of 58 mV dec-1 in an alkaline medium towards the oxygen evolution reaction. DFT calculations show that the Ni-regulated Co-B compound has a lower rate-determining energy barrier for the *OOH intermediate than the mono-Co-B compound, which facilitates the production of more active catalytic sites for an accelerated surface charge-transfer process for the oxygen evolution reaction.

A path recorder algorithm for Multiple Longest Common Subsequences (MLCS) problems.

MOTIVATION: Searching the Longest Common Subsequences of many sequences is called a Multiple Longest Common Subsequence (MLCS) problem which is a very fundamental and challenging problem in many fields of data mining. The existing algorithms cannot be applicable to problems with long and large-scale sequences due to their huge time and space consumption. To efficiently handle large-scale MLCS problems, a Path Recorder Directed Acyclic Graph (PRDAG) model and a novel Path Recorder Algorithm (PRA) are proposed. RESULTS: In PRDAG, we transform the MLCS problem into searching the longest path from the Directed Acyclic Graph (DAG), where each longest path in DAG corresponds to an MLCS. To tackle the problem efficiently, we eliminate all redundant and repeated nodes during the construction of DAG, and for each node, we only maintain the longest paths from the source node to it but ignore all non-longest paths. As a result, the size of the DAG becomes very small, and the memory space and search time will be greatly saved. Empirical experiments have been performed on a standard benchmark set of both DNA sequences and protein sequences. The experimental results demonstrate that our model and algorithm outperform the related leading algorithms, especially for large-scale MLCS problems. AVAILABILITY AND IMPLEMENTATION: This program code is written by the first author and can be available at https://www.ncbi.nlm.nih.gov/nuccore and https://blog.csdn.net/wswguilin. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Distinct Metabolome Changes during Seed Germination of Lettuce (Lactuca sativa L.) in Response to Thermal Stress as Revealed by Untargeted Metabolomics Analysis.

Temperature strongly influences lettuce (Lactuca sativa L.) seed germination. Different lettuce genotypes respond differently to higher temperatures or thermal stress. In this study, we evaluated the germination performance of 304 lettuce accessions incubated at three temperature settings, 21 °C, 28 °C and 35 °C, respectively, for 40 h. At 21 °C, seeds of all 304 accessions germinated with very well an average germination percentage of 87.72%; at 28 °C, the average germination percentage dropped to 42.84% and at 35 °C, the germination decreased to 1.01%. Then, we investigated changes in metabolic profiles of lettuce seed response to thermal stress using an untargeted metabolomics approach. Results suggested that seeds of thermal-sensitive and thermal-tolerant cultivars employed different metabolic strategies in response to thermal stress during germination. Thermal-sensitive buds accumulated more significant amounts of organic acids, amino acids, sugars, sterols, phenolic compounds and terpenoids compared to thermal-tolerant buds at 21 °C. Thermal-tolerant lettuce cultivar accumulated higher concentrations of amino acids, organic acids, sugars, sesquiterpene lactones, sterols, and fatty acids derivatives during the germination at 35 °C compared to germinated at 21 °C. This investigation paves the way to link the metabolomics to other external and internal factors affecting lettuce seed germination under thermal stress.

The Dissipation of Cyazofamid and Its Main Metabolite CCIM During Wine-Making Process.

Few studies have focused on the residues of cyazofamid and its main metabolite CCIM (4-chloro-5-p-tolylimidazole-2-carbonitrile) in the wine making process, which is crucial to evaluate the potential food risk of cyazofamid and CCIM. In this work, detailed study has been conducted on the evaluation of the fate of cyazofamid and its main metabolite CCIM during the wine-making process. The targeted compounds cyazofamid and CCIM were separated and determined by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) and processing procedure including washing, peeling, fermentation, and clarification. Results showed that residues of cyazofamid and CCIM decreased significantly in wine processing. The dissipation of cyazofamid in the fermentation process followed the first-order of kinetics, and the half-life of cyazofamid was 46.2-63.0 h, whereas, the residues of CCIM, in the three treatments, decreased with time elapse. The processing factors (PFs) were all less than one in different processing processes, and the PFs ranges of cyazofamid and CCIM were 0.003-0.025 and 0.039-0.067 in three treatments in the overall process. The outcome indicated that the whole process could significantly reduce the residues of cyazofamid and CCIM in red and white wines. The results might provide more precise risk assessments of cyazofamid in the wine-making process.

A fast and memory efficient MLCS algorithm by character merging for DNA sequences alignment.

MOTIVATION: Multiple longest common subsequence (MLCS) problem is searching all longest common subsequences of multiple character sequences. It appears in many fields such as data mining, DNA alignment, bioinformatics, text editing and so on. With the increasing in sequence length and number of sequences, the existing dynamic programming algorithms and the dominant point-based algorithms become ineffective and inefficient, especially for large-scale MLCS problems. RESULTS: In this paper, by considering the characteristics of DNA sequences with many consecutively repeated characters, we first design a character merging scheme which merges the consecutively repeated characters in the sequences. As a result, it shortens the length of sequences considered and saves the space of storing all sequences. To further reduce the space and time costs, we construct a weighted directed acyclic graph which is much smaller than widely used directed acyclic graph for MLCS problems. Based on these techniques, we propose a fast and memory efficient algorithm for MLCS problems. Finally, the experiments are conducted and the proposed algorithm is compared with several state-of-the art algorithms. The experimental results show that the proposed algorithm performs better than the compared state-of-the art algorithms in both time and space costs. AVAILABILITY AND IMPLEMENTATION: https://www.ncbi.nlm.nih.gov/nuccore and https://github.com/liusen1006/MLCS.

A novel integrated non-targeted metabolomic analysis reveals significant metabolite variations between different lettuce (Lactuca sativa. L) varieties.

Lettuce is an important leafy vegetable that represents a significant dietary source of antioxidants and bioactive compounds. However, the levels of metabolites in different lettuce cultivars are poorly characterized. In this study, we used combined GC × GC-TOF/MS and UPLC-IMS-QTOF/MS to detect and relatively quantify metabolites in 30 lettuce cultivars representing large genetic diversity. Comparison with online databases, the published literature, standards as well using collision cross-section values enabled putative identification of 171 metabolites. Sixteen of these 171 metabolites (including phenolic acid derivatives, glycosylated flavonoids, and one iridoid) were present at significantly different levels in leaf and head type lettuces, which suggested the significant metabolomic variations between the leaf and head types of lettuce are related to secondary metabolism. A combination of the results and metabolic network analysis techniques suggested that leaf and head type lettuces contain not only different levels of metabolites but also have significant variations in the corresponding associated metabolic networks. The novel lettuce metabolite library and novel non-targeted metabolomics strategy devised in this study could be used to further characterize metabolic variations between lettuce cultivars or other plants. Moreover, the findings of this study provide important insight into metabolic adaptations due to natural and human selection, which could stimulate further research to potentially improve lettuce quality, yield, and nutritional value.

The Efficacy of Naikan Therapy on Male Offenders: Changes in Perceived Social Support and Externalized Blame.

Naikan is a contemplative self-observation practice that originated from Japanese Shin Buddhism and is utilized for rehabilitating prison inmates in many countries. Although some investigations have provided initial evidence for its efficiency in decreasing recidivism, there is still a need for further investigation of the effectiveness of Naikan on other outcomes through more controlled studies. The present study aimed to investigate the efficacy of Naikan therapy on male offenders' perceived social support and externalized blame. Ninety-two male offenders were randomly assigned to either the experimental group or to the waiting group. All participants were evaluated by the Multidimensional Scale of Perceived Social Support and the Externalization subscale of the Test of Self-Conscious Affect before and after Naikan therapy. The results suggested that participants who received Naikan therapy showed higher levels of perceived social support and lower levels of externalized blame after Naikan therapy than before.

Exogenous Glycine Nitrogen Enhances Accumulation of Glycosylated Flavonoids and Antioxidant Activity in Lettuce (Lactuca sativa L.).

Glycine, the simplest amino acid in nature and one of the most abundant free amino acids in soil, is regarded as a model nutrient in organic nitrogen studies. To date, many studies have focused on the uptake, metabolism and distribution of organic nitrogen in plants, but few have investigated the nutritional performance of plants supplied with organic nitrogen. Lettuce (Lactuca sativa L.), one of the most widely consumed leafy vegetables worldwide, is a significant source of antioxidants and bioactive compounds such as polyphenols, ascorbic acid and tocopherols. In this study, two lettuce cultivars, Shenxuan 1 and Lollo Rossa, were hydroponically cultured in media containing 4.5, 9, or 18 mM glycine or 9 mM nitrate (control) for 4 weeks, and the levels of health-promoting compounds and antioxidant activity of the lettuce leaf extracts were evaluated. Glycine significantly reduced fresh weight compared to control lettuce, while 9 mM glycine significantly increased fresh weight compared to 4.5 or 18 mM glycine. Compared to controls, glycine (18 mM for Shenxuan 1; 9 mM for Lollo Rossa) significantly increased the levels of most antioxidants (including total polyphenols, α-tocopherol) and antioxidant activity, suggesting appropriate glycine supply promotes antioxidant accumulation and activity. Glycine induced most glycosylated quercetin derivatives and luteolin derivatives detected and decreased some phenolic acids compared to nitrate treatment. This study indicates exogenous glycine supplementation could be used strategically to promote the accumulation of health-promoting compounds and antioxidant activity of hydroponically grown lettuce, which could potentially improve human nutrition.

Genome-wide investigation of the NAC transcription factor family in melon (Cucumis melo L.) and their expression analysis under salt stress.

KEY MESSAGE: 82 melon NAC (CmNAC) genes were identified in melon. We putatively identified the function of CmNAC gene in melon under salt stress. NAC transcription factor proteins play important roles in many biological processes, including plant development and stress responses. To date, few full-length melon NAC proteins have been identified. In this study, 82 melon NAC (CmNAC) genes were identified in the Cucumis melo L. genome. By interrogating our cDNA libraries and transcriptome data from melon under salt stress, and comparison of their phylogenetic relationship with Arabidopsis NAC salt stress-related genes, we putatively identified that the fourth clade of CmNAC genes were involved in the salt stress response, especially the second clade of the group IV of the phylogenetic tree. Expression analysis confirmed that eleven of the twelve CmNAC genes from the group IV were induced in melon seedling roots by salt stress; the other gene was down regulated by salt stress. The expression of CmNAC14 continually increased in 12 h under salt stress, and was selected for transformation into Arabidopsis for functional verification. Overexpression of CmNAC14 increased the sensitivity of transgenic Arabidopsis lines to salt stress, which were simultaneously demonstrated by reduced expression of abiotic stress-response genes and variation in several physiological indices. This study increases our knowledge and may enable further characterization of the roles of CmNAC family in the response to salt stress.

Identification of early response genes to salt stress in roots of melon (Cucumis melo L.) seedlings.

In order to better understand the mechanisms by which muskmelons (Cucumis melo L.) respond to salt stress, a cDNA library was constructed using suppression subtractive hybridization (SSH) from the root tissue of a salt-tolerant melon cultivar, Bingxuecui. A total of 339 clones were sequenced from the SSH library, leading to 312 high quality expressed sequence tags (ESTs), with an average size of 450 bp; representing 262 uni-ESTs comprising 29 contigs and 233 singletons. Blast analysis of the deduced protein sequences revealed that 283 ESTs had a high similarity to proteins in the non-redundant database, while 29 had low identity or no similarities. Many of the annotated sequences were homologous to genes involved in abiotic or biotic stress in plants. Functional categorization of the proteins revealed that salt tolerance could be largely determined by various proteins involved in metabolism, energy, transcription, signal transduction, protein fate, cell rescue and defense, implying a complex response to salt stress exists in melon plants. Twenty-seven ESTs were selected and analyzed by real-time PCR; the results confirmed that a high proportion of the ESTs were activated by salt stress. The complete sequences and a detailed functional analysis of these ESTs is required, in order to fully understand the broader impact of these genes in plants subjected to a high salinity environment.