Distinctive physiological and molecular responses to cold stress among cold-tolerant and cold-sensitive Pinus halepensis seed sources

The physiochemical characteristics and glycerolipid profile of Cycas panzhihuaensis in response to individual and combined drought and freezing temperature stress

The frequency and intensity of the occurrence of drought (D) events during winter are increasing in most areas of China. To explore the interactive effects of D and freezing temperature (F) on plants of endangered Cycas panzhihuaensis, some physiochemical characteristics and the lipid profile were determined. Drought and F stress had no or little impact on the traits of leaves, which, however, bleached following a combination of D and F treatment (DF). Drought treatment did not affect the chlorophyll fluorescence parameters and the flavonoid content of C. panzhihuaensis. Besides the increase in flavonoid content, a decrease of photochemical efficiency and an increase of heat dissipation were induced by both F and DF treatment, with the effects being greater in the latter treatment. The malondialdehyde content decreased significantly and the total antioxidant capacity increased significantly in the plants exposed to both D and DF treatments. The D treatment did not impact the amount of phospholipids but led to an accumulation of saccharolipids. Additionally, the amount of both phospholipids and saccharolipids remained unchanged following F treatment but decreased significantly following DF treatment compared with those of the control. The unsaturation level did not change significantly in most lipid classes of membrane glycerolipids following various stresses but increased significantly in phosphatidylserine, monogalactosylmonoacylglycerol, digalactosyldiacylglycerol and sulphoquinovosyldiacylglycerol following D or both D and F treatments. Generally, plants of C. panzhihuaensis showed relatively strong tolerance to individual D stress, while D aggravated the F-induced damage, which was likely caused by the degradation of the membrane glycerolipids.

Integrative physiological, transcriptomic and metabolomic analysis reveals how the roots of two ornamental Hydrangea macrophylla cultivars cope with lead (Pb) toxicity

Lead (Pb) soil contamination has caused serious ecological and environmental issues. Hydrangea macrophylla is a potential Pb-contaminated soil remediation plant, however, their Pb stress defense mechanism is largely unknown. Here, the physiology, transcriptomic and metabolome of two H. macrophylla cultivars (ML, Pb-sensitive cultivar; JC, Pb-resistant cultivar) under Pb stress were investigated. The results demonstrated that JC performed superiorly, with activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were 1.25, 2.84, and 1.67 times higher than those of ML after Pb treatment, respectively, and the amount of soluble sugar in JC increased by 231.34 % compared with that in ML. The electrical conductivity (EC) value of the root exudates of JC was 43.71 % lower than that of ML under Pb stress. The non-targeted metabolomics analysis revealed 193 metabolites grouped into nine categories. Pb stress-induced differential expression of the 37 metabolites, among which the major metabolites up-regulated in ML were organic acids, while in JC, these were carbohydrates, fatty acids, organic acids and lipids. The transcriptomic analysis revealed that Pb exposure induced 1075 and 1314 differentially expressed genes (DEGs) in JC and ML, respectively. According to the functional annotation results, hub genes were primarily enriched in carbohydrate metabolism, root growth, and plant resistance to external stresses. A conjoint analysis of the two omics indicated that the cutin, suberine and wax biosynthesis pathway in JC played an essential role in Pb detoxification. These findings clarify the resistance mechanism of H. macrophylla to Pb stress and open up a new avenue for breeding H. macrophylla Pb-resistant cultivars.

Metabolomic Analysis of the Effect of Freezing on Leaves of Malus sieversii (Ledeb.) M.Roem. Histoculture Seedlings

Malus sieversii (Ledeb.) M.Roem. is the ancestor of cultivated apples, and is an excellent germplasm resource with high resistance to cold. Artificial refrigerators were used to simulate the low temperature of -3 °C to treat Malus sieversii (Ledeb.) M.Roem. histoculture seedlings. Observations were performed to find the effects of freezing stress on the status of open or closed stomata, photosystems, and detection of metabolomic products in leaves of Malus sieversii (Ledeb.) M.Roem. histoculture seedlings. The percentage of closed stomata in the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings increased, the maximum fluorescence (Fm') excited by a strong light (saturating pulse) was weakened relative to the real-time fluorescence in its vicinity, and the quantum yield of unregulated energy dissipation was increased in PSII under freezing stress. The metabolites in the leaves of the Malus sieversii (Ledeb. M.Roem.) histoculture seedlings were analyzed by ultra-performance liquid chromatography-tandem mass spectrometry using CK, T12h, T36 h, and HF24h. Results demonstrated that cold stress in the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings led to wilting, leaf stomatal closure, and photosystem damage. There were 1020 metabolites identified as lipids (10.2%), nucleotides and their derivatives (5.2%), phenolic acids (19.12%), flavonoids (24.51%), amino acids and their derivatives (7.75%), alkaloids (5.39%), terpenoids (8.24%), lignans (3.04%), organic acids (5.88%), and tannins (0.88%). There were 110 differential metabolites at CKvsT12h, 113 differential metabolites at CKvsT36h, 87 differential metabolites at T12hvsT36h, 128 differential metabolites at CKvsHF24h, 121 differential metabolites at T12hvsHF24h, and 152 differential metabolites at T36hvsHF24h. The differential metabolites in the leaves of the Malus sieversii (Ledeb.) M.Roem. seedlings grown under low-temperature stress mainly involved glycolysis, amino acid metabolism, lipid metabolism, pyrimidine metabolism, purine metabolism, and secondary metabolite metabolism. The Malus sieversii (Ledeb.) M.Roem. seedlings responded to the freezing stress by coordinating with each other through these metabolic pathways. The metabolic network of the leaves of the Malus sieversii (Ledeb.) M.Roem. histoculture seedlings under low temperature stress was also proposed based on the above pathways to deepen understanding of the response of metabolites of Malus sieversii (Ledeb.) M.Roem. to low-temperature stress and to lay a theoretical foundation for the development and utilization of Malus sieversii (Ledeb.) M.Roem. cultivation resources.

The metabolism of nonstructural carbohydrates, lipids, and energy in two Cycas species with differential tolerance to unexpected freezing stress

Introduction

With the climate warming, the occurrence of freezing events is projected to increase in late spring and early autumn in the Northern Hemisphere. Observation of morphological traits showed that Cycas panzhihuaensis was more tolerant to unexpected freezing stress than C. bifida. Energy balance is crucial for plant tolerance to stress. Here, we aimed to determine whether the different responses of the two species to the unpredicted freezing stress were associated with the metabolism of energy and related substances.

Methods

The effects of unexpected freezing temperatures on C. panzhihuaensis and C. bifida were studied by measuring chlorophyll fluorescence parameters, energy charge and the profile of nonstructural carbohydrates (NSC) and lipids.

Results

C. panzhihuaensis exhibited higher stability of photosynthetic machinery than C. bifida under unpredicted freezing events. Significant interaction between species and treatments were observed in the energy charge, the level of NSC and its most components and the amount of most lipid categories and lipid classes. The decrease of soluble sugar and the increase of neutral glycerolipids at the early freezing stage, the accumulation of membrane glycerolipids at the late freezing stage and the continuous decrease of energy charge during the freezing period were the characteristics of C. panzhihuaensis responding to unexpected freezing stress. The degradation of membrane glycerolipids and the continuous decrease of soluble sugar during the freezing period and the accumulation of neutral glycerolipids and energy charge at the late freezing stage represented the characteristics of C. bifida responses.

Discussion

The different freezing sensitivity between C. panzhihuaensis and C. bifida might be associated with the differential patterns of the metabolism of energy, NSC and lipids. C. panzhihuaensis possesses the potential to be introduced to the areas of higher latitudes and altitudes.

Negative regulation of tobacco cold stress tolerance by NtPhyA

Cold stress is a non-biological stressor that adversely affects tobacco yield and leaf quality. Plant photoreceptor proteins, which function as dual light-temperature sensors, play a vital role in temperature changes, making them crucial for responses to non-biological stressors. However, the regulatory mechanisms of PhyA in tobacco remain poorly understood. Therefore, in this study, we aimed to clone the NtPhyA gene from tobacco and generate overexpression (OE-NtPhyA) and mutant (KO-NtPhyA) constructs of NtPhyA. By assessing the physiological and biochemical responses of the mutants under cold stress and performing transcriptome sequencing, we determined the signalling mechanism of NtPhyA under cold stress. Comparative analysis with wild-type (WT) NtPhyA revealed that KO-NtPhyA exhibited increased seed germination rates and reduced wilting under cold stress. In additional, the degree of damage to leaf cells, cell membranes, and stomatal structures was mitigated, and the levels of reactive oxygen species (ROS) were significantly decreased. Antioxidant enzyme activity, net photosynthetic rate, and Fv/Fm were significantly enhanced in KO-NtPhyA, whereas the opposite effects were observed in OE-NtPhyA. These findings indicate that KO-NtPhyA augments tobacco tolerance to cold stress, implying a negative regulatory role of NtPhyA in tobacco during cold stress. Transcriptome analysis revealed that NtPhyA governs the expression of a cascade of genes involved in the response to oxygen-containing compounds, hydrogen peroxide (H2O2), ROS, temperature stimuli, photosystem II oxygen-evolving complex assembly, water channel activity, calcium channel activity, and carbohydrate transport. Collectively, our findings indicate that NtPhyA activates downstream gene expression to enhance the resilience of tobacco to cold stress.

Integrated Transcriptomic and Metabolomics Analyses Reveal Molecular Responses to Cold Stress in Coconut (Cocos nucifera L.) Seedlings

Coconut is an important tropical and subtropical fruit and oil crop severely affected by cold temperature, limiting its distribution and application. Thus, studying its low-temperature reaction mechanism is required to expand its cultivation range. We used growth morphology and physiological analyses to characterize the response of coconuts to 10, 20, and 30 d of low temperatures, combined with transcriptome and metabolome analysis. Low-temperature treatment significantly reduced the plant height and dry weight of coconut seedlings. The contents of soil and plant analyzer development (SPAD), soluble sugar (SS), soluble protein (SP), proline (Pro), and malondialdehyde (MDA) in leaves were significantly increased, along with the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and the endogenous hormones abscisic acid (ABA), auxin (IAA), zeatin (ZR), and gibberellin (GA) contents. A large number of differentially expressed genes (DEGs) (9968) were detected under low-temperature conditions. Most DEGs were involved in mitogen-activated protein kinase (MAPK) signaling pathway-plant, plant hormone signal transduction, plant-pathogen interaction, biosynthesis of amino acids, amino sugar and nucleotide sugar metabolism, carbon metabolism, starch and sucrose metabolism, purine metabolism, and phenylpropanoid biosynthesis pathways. Transcription factors (TFs), including WRKY, AP2/ERF, HSF, bZIP, MYB, and bHLH families, were induced to significantly differentially express under cold stress. In addition, most genes associated with major cold-tolerance pathways, such as the ICE-CBF-COR, MAPK signaling, and endogenous hormones and their signaling pathways, were significantly up-regulated. Under low temperatures, a total of 205 differentially accumulated metabolites (DAMs) were enriched; 206 DAMs were in positive-ion mode and 97 in negative-ion mode, mainly including phenylpropanoids and polyketides, lipids and lipid-like molecules, benzenoids, organoheterocyclic compounds, organic oxygen compounds, organic acids and derivatives, nucleosides, nucleotides, and analogues. Comprehensive metabolome and transcriptome analysis revealed that the related genes and metabolites were mainly enriched in amino acid, flavonoid, carbohydrate, lipid, and nucleotide metabolism pathways under cold stress. Together, the results of this study provide important insights into the response of coconuts to cold stress, which will reveal the underlying molecular mechanisms and help in coconut screening and breeding.

De Novo Transcriptome Assembly and Comparative Analysis of Differentially Expressed Genes Involved in Cold Acclimation and Freezing Tolerance of the Arctic Moss Aulacomnium turgidum (Wahlenb.) Schwaegr

Cold acclimation refers to a phenomenon in which plants become more tolerant to freezing after exposure to non-lethal low temperatures. Aulacomnium turgidum (Wahlenb.) Schwaegr is a moss found in the Arctic that can be used to study the freezing tolerance of bryophytes. To improve our understanding of the cold acclimation effect on the freezing tolerance of A. turgidum, we compared the electrolyte leakage of protonema grown at 25 °C (non-acclimation; NA) and at 4 °C (cold acclimation; CA). Freezing damage was significantly lower in CA plants frozen at -12 °C (CA-12) than in NA plants frozen at -12 °C (NA-12). During recovery at 25 °C, CA-12 demonstrated a more rapid and greater level of the maximum photochemical efficiency of photosystem II than NA-12, indicating a greater recovery capacity for CA-12 compared to NA-12. For the comparative analysis of the transcriptome between NA-12 and CA-12, six cDNA libraries were constructed in triplicate, and RNA-seq reads were assembled into 45,796 unigenes. The differential gene expression analysis showed that a significant number of AP2 transcription factor genes and pentatricopeptide repeat protein-coding genes related to abiotic stress and the sugar metabolism pathway were upregulated in CA-12. Furthermore, starch and maltose concentrations increased in CA-12, suggesting that cold acclimation increases freezing tolerance and protects photosynthetic efficiency through the accumulation of starch and maltose in A. turgidum. A de novo assembled transcriptome can be used to explore genetic sources in non-model organisms.

Indoleamines Impart Abiotic Stress Tolerance and Improve Reproductive Traits in Hazelnuts

Hazelnuts have recently gathered tremendous attention due to the expansion of the confectionary industry. However, the sourced cultivars fail to perform in initial phase of cultivation as they enter bare survival mode due to changes in climatic zones, for example, Southern Ontario, where the climate is continental, as opposed to the milder climate in Europe and Turkey. Indoleamines have been shown to counter abiotic stress and modulate vegetative and reproductive development of plants. Here, we examined the effect of indoleamines on the flowering response of the dormant stem cuttings of sourced hazelnut cultivars in controlled environment chambers. The stem cuttings were exposed to sudden summer-like conditions (abiotic stress) and the female flower development was assessed in relation to endogenous indoleamine titers. The sourced cultivars responded well to serotonin treatment by producing more flowers compared to the controls or other treatments. The probability of buds resulting in female flowers was highest in the middle region of the stem cuttings. It is interesting to note that the tryptamine titers of the locally adapted, and N-acetyl serotonin titers of native hazelnut cultivars, provided the best explanation for adaptation to the stress environment. Titers of both compounds were compromised in the sourced cultivars which resorted mostly to serotonin concentrations to counter the stress. The indoleamines tool kit identified in this study could be deployed in assessing cultivars for stress adaptation attributes.

Drought priming triggers diverse metabolic adjustments and induces chilling tolerance in chickpea (Cicer arietinum L.)

Chickpea (Cicer arietinum L.) suffers from chilling stress at the reproductive stage (<15 °C) which leads to significant yield loss. This study presents a comprehensive plant response to drought priming and its effect on chilling tolerance during the reproductive stage in two chickpea cultivars PBG1 and PBG5. Lipidome profiling (Fatty acid methyl esters analysis), metabolome profiling (GC-MS based untargeted analysis), fatty acid desaturases and antioxidative gene expression (qRT-PCR) were analyzed to monitor physiological and biochemical events after priming during flowering, podding and seed filling stages. Drought priming alleviated membrane damage and chlorophyll degradation by increasing membrane unsaturated fatty acids (18:3) along with up-regulation of various fatty acid desaturases (CaFADs) genes and antioxidative machinery during flowering and improved seed yield in PBG5. PCA, HCA, and KEGG pathway analysis of 87 identified metabolites showed that metabolites were regulated differently in both cultivars under non-primed and primed conditions. The plant response was more apparent at flowering and podding stages which coincided with chilling temperature (<15 °C). Drought priming stimulated many important genes, especially FADs, antioxidative proteins and accumulation of key metabolites (proline and TCA intermediates) required for defense especially in PBG5. This explains that plant's response to drought priming not only depends on developmental stage, and temperature regime (<15 °C) but also on the genotypic-specificity.

Drought priming induces chilling tolerance and improves reproductive functioning in chickpea (Cicer arietinum L.)

Priming alleviates membrane damage, chlorophyll degradation along with cryoprotectants accumulation during chilling stress that leads to improved reproductive functioning and increased seed yield. Chilling temperatures below 15 °C have severe implications on the reproductive growth and development of chickpea. The abnormal reproductive development and subsequent reproductive failure lead to substantial yield loss. We exposed five chickpea cultivars (PBG1, GPF2, PDG3, PDG4, and PBG5) to drought stress (Priming) during the vegetative stage and analyzed for chilling tolerance during the reproductive stage. These varieties were raised in the fields in two sets: one set of plants were subjected to drought stress at the vegetative stage for 30 days (priming) and the second set of plants were irrigated regularly (non-primed). The leaf samples were harvested at the flowering, podding, and seed filling stage and analyzed for membrane damage, water status, chlorophyll content, cellular respiration, and certain cryoprotective solutes. The reproductive development was analyzed by accessing pollen viability, in vivo and in vitro germination, pollen load, and in vivo pollen tube growth. Principal component analysis (PCA) revealed that priming improved membrane damage, chlorophyll b degradation, and accumulation of cryoprotectants in GPF2, PDG3, and PBG5 at the flowering stage (< 15 °C). Pearson's correlation analysis showed a negative correlation with the accumulation of proline and carbohydrates with flower, pod, and seed abortion. Only, PBG5 responded best to priming while PBG1 was worst. In PBG5, priming resulted in reduced membrane damage and lipid peroxidation, improved water content, reduced chlorophyll degradation, and enhanced cryoprotective solutes accumulation, which led to increased reproductive functioning and finally improved seed yield and harvest index. Lastly, the priming response is variable and cultivar-specific but overall improve plant tolerance.

The mechanism of abscisic acid regulation of wild Fragaria species in response to cold stress

Background

Abiotic stresses have increasingly serious effects on the growth and yield of crops. Cold stress, in particular, is an increasing problem. In this study, Fragaria daltoniana and F. vesca were determined to be cold-resistant and cold-sensitive species, respectively. Integrated transcriptomics and metabolomics methods were used to analyze the regulatory mechanism of abscisic acid (ABA) in F. daltoniana and F. vesca in their response to low temperature stress.

Results

F. daltoniana and F. vesca increased their ABA content under low temperature stress by upregulating the expression of the ABA biosynthetic pathway gene NCED and downregulating the expression of the ABA degradative gene CYP707A. Both types of regulation increased the accumulation of glucose and fructose, resulting in a reduction of damage under low temperature stress. Twelve transcription factors were found to be involved in the ABA regulatory pathway. The strong cold tolerance of F. daltoniana could be owing to its higher levels of ABA that accumulated compared with those in F. vesca under low temperature stress. In addition, the gene ABF2, which is related to the transduction of glucose signaling, was significantly upregulated in the leaves of F. daltoniana, while it was downregulated in the leaves of F. vesca under low temperature stress. This could contribute to the higher levels of glucose signal transduction in F. daltoniana. Thus, this could explain the higher peroxidase activity and lower damage to cell membranes in the leaves of F. daltoniana compared with F. vesca under low temperature stress, which endows the former with stronger cold tolerance.

Conclusions

Under low temperature stress, the differences in the accumulation of ABA and the expression trends of ABF2 and ABF4 in different species of wild strawberries may be the primary reason for their differences in cold tolerance. Our results provide an important empirical reference and technical support for breeding resistant cultivated strawberry plants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08889-8.

Comparative transcriptomic analyses of citrus cold-resistant vs. sensitive rootstocks might suggest a relevant role of ABA signaling in triggering cold scion adaption

BACKGROUND

The citrus genus comprises a number of sensitive tropical and subtropical species to cold stress, which limits global citrus distribution to certain latitudes and causes major economic loss. We used RNA-Seq technology to analyze changes in the transcriptome of Valencia delta seedless orange in response to long-term cold stress grafted on two frequently used citrus rootstocks: Carrizo citrange (CAR), considered one of the most cold-tolerant accessions; C. macrophylla (MAC), a very sensitive one. Our objectives were to identify the genetic mechanism that produce the tolerant or sensitive phenotypes in citrus, as well as to gain insights of the rootstock-scion interactions that induce the cold tolerance or sensitivity in the scion.

RESULTS

Plants were kept at 1 ºC for 30 days. Samples were taken at 0, 15 and 30 days. The metabolomic analysis showed a significant increase in the concentration of free sugars and proline, which was higher for the CAR plants. Hormone quantification in roots showed a substantially increased ABA concentration during cold exposure in the CAR roots, which was not observed in MAC. Different approaches were followed to analyze gene expression. During the stress treatment, the 0-15-day comparison yielded the most DEGs. The functional characterization of DEGs showed enrichment in GO terms and KEGG pathways related to abiotic stress responses previously described in plant cold adaption. The DEGs analysis revealed that several key genes promoting cold adaption were up-regulated in the CAR plants, and those repressing it had higher expression levels in the MAC samples.

CONCLUSIONS

The metabolomic and transcriptomic study herein performed indicates that the mechanisms activated in plants shortly after cold exposure remain active in the long term. Both the hormone quantification and differential expression analysis suggest that ABA signaling might play a relevant role in promoting the cold hardiness or sensitiveness of Valencia sweet orange grafted onto Carrizo citrange or Macrophylla rootstocks, respectively. Our work provides new insights into the mechanisms by which rootstocks modulate resistance to abiotic stress in the production variety grafted onto them.

Comparative transcriptome analysis of cold-tolerant and -sensitive asparagus bean under chilling stress and recovery

Background

Low temperature is a type of abiotic stress that threatens the growth and yield of asparagus bean. However, the key genes and regulatory pathways involved in low temperature response in this legume are still poorly understood. Methodology. The present study analyzed the transcriptome of seedlings from two asparagus bean cultivars-Dubai bean and Ningjiang 3-using Illumina RNA sequencing (RNA-seq). Correlations between samples were determined by calculating Pearson correlation coefficients (PCC) and principal component analysis (PCA). Differentially expressed genes (DEGs) between two samples were identified using the DESeq package. Transcription factors (TF) prediction, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs were also performed.

Results

Phenotypes and physiological indices indicated that Ningjiang 3 seedlings tolerated cold better than Dubai bean seedlings, in contrast to adult stage. The transcriptome dynamics of the two cultivars were closely compared using Illumina RNA-seq following 0, 3, 12, and 24 h of cold stress at 5 °C and recovery for 3 h at 25 °C room temperature. Global gene expression patterns displayed relatively high correlation between the two cultivars (>0.88), decreasing to 0.79 and 0.81, respectively, at 12 and 24 h of recovery, consistent with the results of principal component analysis. The major transcription factor families identified from differentially expressed genes between the two cultivars included bHLH, NAC, C2H2, MYB, WRKY, and AP2/ERF. The representative GO enrichment terms were protein phosphorylation, photosynthesis, oxidation-reduction process, and cellular glucan metabolic process. Moreover, KEGG analysis of DEGs within each cultivar revealed 36 transcription factors enriched in Dubai bean and Ningjiang 3 seedlings under cold stress.

Conclusions

These results reveal new information that will improve our understanding of the molecular mechanisms underlying the cold stress response of asparagus bean and provide genetic resources for breeding cold-tolerant asparagus bean cultivars.

A constitutive stress response is a result of low temperature growth in the Antarctic green alga Chlamydomonas sp. UWO241

The Antarctic green alga Chlamydomonas sp. UWO241 is an obligate psychrophile that thrives in the cold (4-6°C) but is unable to survive at temperatures ≥18°C. Little is known how exposure to heat affects its physiology or whether it mounts a heat stress response in a manner comparable to mesophiles. Here, we dissect the responses of UWO241 to temperature stress by examining its growth, primary metabolome and transcriptome under steady-state low temperature and heat stress conditions. In comparison with Chlamydomonas reinhardtii, UWO241 constitutively accumulates metabolites and proteins commonly considered as stress markers, including soluble sugars, antioxidants, polyamines, and heat shock proteins to ensure efficient protein folding at low temperatures. We propose that this results from life at extreme conditions. A shift from 4°C to a non-permissive temperature of 24°C alters the UWO241 primary metabolome and transcriptome, but growth of UWO241 at higher permissive temperatures (10 and 15°C) does not provide enhanced heat protection. UWO241 also fails to induce the accumulation of HSPs when exposed to heat, suggesting that it has lost the ability to fine-tune its heat stress response. Our work adds to the growing body of research on temperature stress in psychrophiles, many of which are threatened by climate change.

Distinctive Traits for Drought and Salt Stress Tolerance in Melon (Cucumis melo L.)

Melon (Cucumis melo L.) is a crop with important agronomic interest worldwide. Because of the increase of drought and salinity in many cultivation areas as a result of anthropogenic global warming, the obtention of varieties tolerant to these conditions is a major objective for agronomical improvement. The identification of the limiting factors for stress tolerance could help to define the objectives and the traits which could be improved by classical breeding or other techniques. With this objective, we have characterized, at the physiological and biochemical levels, two different cultivars (sensitive or tolerant) of two different melon varieties (Galia and Piel de Sapo) under controlled drought or salt stress. We have performed physiological measurements, a complete amino acid profile and we have determined the sodium, potassium and hormone concentrations. This has allowed us to determine that the distinctive general trait for salt tolerance in melon are the levels of phenylalanine, histidine, proline and the Na⁺/K⁺ ratio, while the distinctive traits for drought tolerance are the hydric potential, isoleucine, glycine, phenylalanine, tryptophan, serine, and asparagine. These could be useful markers for breeding strategies or to predict which varieties are likely perform better under drought or salt stress. Our study has also allowed us to identify which metabolites and physiological traits are differentially regulated upon salt and drought stress between different varieties.

Identification of distinctive physiological and molecular responses to salt stress among tolerant and sensitive cultivars of broccoli (Brassica oleracea var. Italica)

BACKGROUND

Salt stress is one of the main constraints determining crop productivity, and therefore one of the main limitations for food production. The aim of this study was to characterize the salt stress response at the physiological and molecular level of different Broccoli (Brassica oleracea L. var. Italica Plenck) cultivars that were previously characterized in field and greenhouse trials as salt sensitive or salt tolerant. This study aimed to identify functional and molecular traits capable of predicting the ability of uncharacterized lines to cope with salt stress. For this purpose, this study measured different physiological parameters, hormones and metabolites under control and salt stress conditions.

RESULTS

This study found significant differences among cultivars for stomatal conductance, transpiration, methionine, proline, threonine, abscisic acid, jasmonic acid and indolacetic acid. Salt tolerant cultivars were shown to accumulate less sodium and potassium in leaves and have a lower sodium to potassium ratio under salt stress. Analysis of primary metabolites indicated that salt tolerant cultivars have higher concentrations of several intermediates of the Krebs cycle and the substrates of some anaplerotic reactions.

CONCLUSIONS

This study has found that the energetic status of the plant, the sodium extrusion and the proline content are the limiting factors for broccoli tolerance to salt stress. Our results establish physiological and molecular traits useful as distinctive markers to predict salt tolerance in Broccoli or to design novel biotechnological or breeding strategies for improving broccoli tolerance to salt stress.

Physiological and Molecular Characterization of the Differential Response of Broccoli (Brassica oleracea var. Italica) Cultivars Reveals Limiting Factors for Broccoli Tolerance to Drought Stress

Broccoli is a cruciferous crop rich in health-promoting metabolites. Due to several factors, including anthropogenic global warming, aridity is increasing in many cultivation areas. There is a great demand to characterize the drought response of broccoli and use this knowledge to develop new cultivars able to maintain yield under water constraints. The aim of this study is to characterize the drought response at the physiological and molecular level of different broccoli (Brassica oleracea L. var. Italica Plenck) cultivars, previously characterized as drought-sensitive or drought-tolerant. This approach aims to identify different traits, which can constitute limiting factors for drought stress tolerance in broccoli. For this purpose, we have compared several physiological parameters and the complete profiles of amino acids, primary metabolites, hormones, and ions of drought-tolerant and drought-sensitive cultivars under stress and control conditions. We have found that drought-tolerant cultivars presented higher levels of methionine and abscisic acid and lower amounts of urea, quinic acid, and the gluconic acid lactone. Interestingly, we have also found that a drought treatment increases the levels of most essential amino acids in leaves and in florets. Our results have established physiological and molecular traits useful as distinctive markers to predict drought tolerance in broccoli or which could be reliably used for breeding new cultivars adapted to water scarcity. We have also found that a drought treatment increases the content of essential amino acids in broccoli.

Clinical Analysis and Proteomic Screening Biomarkers for Graft-Versus-Host Disease After Liver Transplant

OBJECTIVES

Graft-versus-host disease is a serious, fatal complication following liver transplantation. The diagnosis is challenging, owing to nonspecific clinical features and invasive procedures. High-throughput proteomics could provide an effective approach to identifying potential serum biomarkers for graft-versus-host disease.

MATERIALS AND METHODS

We retrospectively analyzed the clinical information of 3 patients with graft-versus-host disease treated at our center from 2016 to 2018. We compared serum samples from the 3 patients with the disease, patients with excellent posttransplant outcomes, and healthy controls using mass spectrometry-based proteomics in discovery study. Probable peptides were further identified by a tandem mass spectrometry system and verified by enzyme-linked immunosorbent assay.

RESULTS

Of 343 patients, 3 patients (0.875%) had graft-versus-host disease. Two of these patients died of sepsis and multiorgan failure despite intensive therapy. We observed no correlation between severity of clinical manifestation and prognosis; however, the patients with graft-versus-host disease had early onset and infection and showed worse outcome. Serum peptidome profiling showed 65 differentially expressed peaks among the 3 groups; the 2 peptides with the most significant changes (m/z values of 1950.29 and 2088.16) were further sequenced and identified as ATP citrate lyase and fibrinogen alpha chain. Western blot and enzyme-linked immunosorbent assay showed that both peptides gradually decreased among all groups.

CONCLUSIONS

Graft-versus-host disease is a complication of organ and tissue transplantation with a high mortality rate. Our identification of potential biomarkers for graft-versus-host disease associated with liver transplant may aid in diagnosis and help to reduce patient mortality in those cases.

Characterization of Phytochemical Components of Crocus sativus Leaves: A New Attractive By-Product

Crocus sativus L. is one of the world’s most famous saffron production crops and its enormous by-products, such as leaves, are an excellent source of bioactive compounds with potential nutritional applications. The total phenolic content of Crocus leaves was 5.44 ± 0.01 mg GAE/g, and the total flavonoid content was 2.63 ± 0.05 mg RE/g, respectively. The main bioactive compounds in the leaves, such as polyphenols, flavonoids by HPLC and carboxylic acids, and amino acids, were also identified by GC-MS. HPLC analyses revealed mangiferin as a dominant constituent (1.26 ± 0.02 mg/g). C. sativus contains seven essential amino acids (ILE, LEU, LYS, MET, PHE, THR, TRP, VAL) in high concentration. Among them, isoleucine (7965 µg/g) was the dominant compound. In addition, the K and Ca concentrations in the leaves were significant (p < 0.05). The chemical composition revealed α-linolenic acid (22,490 µg/g) and linoelaidic acid (9880 µg/g) to be major constituents among all the acids found in the Crocus leaves. The extracts of C. sativus leaves showed the highest inhibitory activity for Gram-positive (B. subtilis and S. aureus) bacteria in the in vitro assay. The current results identify and underline the potential of natural products from C. sativus leaves that can add value to saffron production.

Mass spectrometry-based forest tree metabolomics

Research in forest tree species has advanced slowly when compared with other agricultural crops and model organisms, mainly due to the long-life cycles, large genome sizes, and lack of genomic tools. Additionally, trees are complex matrices, and the presence of interferents (e.g., oleoresins and cellulose) challenges the analysis of tree tissues with mass spectrometry (MS)-based analytical platforms. In this review, advances in MS-based forest tree metabolomics are discussed. Given their economic and ecological significance, particular focus is given to Pinus, Quercus, and Eucalyptus forest tree species to better understand their metabolite responses to abiotic and biotic stresses in the current climate change scenario. Furthermore, MS-based metabolomics technologies produce large and complex datasets that require expertize to adequately manage, process, analyze, and store the data in dedicated repositories. To ensure that the full potential of forest tree metabolomics data are translated into new knowledge, these data should comply with the FAIR principles (i.e., Findable, Accessible, Interoperable, and Re-usable). It is essential that adequate standards are implemented to annotate metadata from forest tree metabolomics studies as is already required by many science and governmental agencies and some major scientific publishers. © 2019 John Wiley & Sons Ltd. Mass Spec Rev 40:126-157, 2021.

Identification of differentially expressed genes involved in amino acid and lipid accumulation of winter turnip rape (Brassica rapa L.) in response to cold stress

Winter turnip rape (Brassica rapa L.) is an important overwintering oil crop that is widely planted in northwestern China. It considered to be a good genetic resource for cold-tolerant research because its roots can survive harsh winter conditions. Here, we performed comparative transcriptomics analysis of the roots of two winter turnip rape varieties, Longyou7 (L7, strong cold tolerance) and Tianyou2 (T2, low cold tolerance), under normal condition (CK) and cold stress (CT) condition. A total of 8,366 differentially expressed genes (DEGs) were detected between the two L7 root groups (L7CK_VS_L7CT), and 8,106 DEGs were detected for T2CK_VS_T2CT. Among the DEGs, two ω-3 fatty acid desaturase (FAD3), two delta-9 acyl-lipid desaturase 2 (ADS2), one diacylglycerol kinase (DGK), and one 3-ketoacyl-CoA synthase 2 (KCS2) were differentially expressed in the two varieties and identified to be related to fatty acid synthesis. Four glutamine synthetase cytosolic isozymes (GLN), serine acetyltransferase 1 (SAT1), and serine acetyltransferase 3 (SAT3) were down-regulated under cold stress, while S-adenosylmethionine decarboxylase proenzyme 1 (AMD1) had an up-regulation tendency in response to cold stress in the two samples. Moreover, the delta-1-pyrroline-5-carboxylate synthase (P5CS), δ-ornithine aminotransferase (δ-OAT), alanine-glyoxylate transaminase (AGXT), branched-chain-amino-acid transaminase (ilvE), alpha-aminoadipic semialdehyde synthase (AASS), Tyrosine aminotransferase (TAT) and arginine decarboxylase related to amino acid metabolism were identified in two cultivars variously expressed under cold stress. The above DEGs related to amino acid metabolism were suspected to the reason for amino acids content change. The RNA-seq data were validated by real-time quantitative RT-PCR of 19 randomly selected genes. The findings of our study provide the gene expression profile between two varieties of winter turnip rape, which lay the foundation for a deeper understanding of the highly complex regulatory mechanisms in plants during cold treatment.

Ethnopharmacological study of natural products used for traditional cancer therapy in Algeria

Traditional and complementary medicine constitutes an important, and often underestimated, source of healthcare for multiple diseases including cancer. However, little is known about the ethnomedical knowledge and practices in Northern Africa. The main objective of this study is to identify and analyze the variety of natural products used in Algerian ethnopharmacology for cancer therapy. For this purpose, semi-structured interviews with 225 traditional healers, herbalists and practitioners were realized in twelve locations in Algeria throughout field studies performed from June 2015 to July 2019. Interviews covered popular and vernacular names of the natural product, mode of use and administration, dose, period of treatment, toxicity and side effects among other data. The obtained results reveal the use of 113 medicinal plants (belonging to 53 families and 104 genera), 10 animal species and various products and by-products from different origins such as honey, olive oil, thorns, urine, milk, animal fat and the alkaline water of Zamzam. Basing on the frequency of citation (FC), use reports (UR) and use value (UV), the most used natural products for cancer treatment are honey (FC = 181, UR = 194, UV = 0.65), Nigella sativa L. (FC = 131, UR = 152, UV = 0.54), Aristolochia longa L. (FC = 118, UR = 144, UV = 0.51), Berberis vulgaris L. (FC = 111, UR = 142, UV = 0.51), Curcuma longa L. (FC = 107, UR = 121, UV = 0.43), Trigonella foenum-graecum L. (FC = 102; UR = 119, UV = 0.43), Citrus limon (L.) Obseck (FC = 97, UR = 120, UV = 0.43), Artemisia herba-alba Asso (FC = 92, UR = 115, UV = 0.41) and the holy water 'Zamzam' (FC = 110, UR = 110, UV = 0.43) respectively. Mixtures of two or more ingredients were frequently used. The use of Pelophylax saharicus skin' was reported for the first time for the treatment of visible tumors and skin cancer. This is the first study documenting the traditional uses of various natural products for cancer treatment in Algeria. Our findings are relevant to document the traditional uses of numerous natural products and to provide background basis to search for novel compounds for cancer therapy.

Transcriptomic diversity in seedling roots of European flint maize in response to cold

BACKGROUND

Low temperatures decrease the capacity for biomass production and lead to growth retardation up to irreversible cellular damage in modern maize cultivars. European flint landraces are an untapped genetic resource for genes and alleles conferring cold tolerance which they acquired during their adaptation to the agroecological conditions in Europe.

RESULTS

Based on a phenotyping experiment of 276 doubled haploid lines derived from the European flint landrace "Petkuser Ferdinand Rot" diverging for cold tolerance, we selected 21 of these lines for an RNA-seq experiment. The different genotypes showed highly variable transcriptomic responses to cold. We identified 148, 3254 and 563 genes differentially expressed with respect to cold treatment, cold tolerance and growth rate at cold, respectively. Gene ontology (GO) term enrichment demonstrated that the detoxification of reactive oxygen species is associated with cold tolerance, whereas amino acids might play a crucial role as antioxidant precursors and signaling molecules.

CONCLUSION

Doubled haploids representing a European maize flint landrace display genotype-specific transcriptome patterns associated with cold response, cold tolerance and seedling growth rate at cold. Identification of cold regulated genes in European flint germplasm, could be a starting point for introgressing such alleles in modern breeding material for maize improvement.

Photosynthesis in Ranunculus asiaticus L.: The Influence of the Hybrid and the Preparation Procedure of Tuberous Roots

Ranunculus asiaticus L. is a quantitative long-day geophyte, grown in a cold greenhouse for cut flowers and potted plants. Flowering in ranunculus is a complex process, strongly steered by temperature and photoperiodism. Vernalization of rehydrated tuberous roots anticipate sprouting and leaf rosette formation and flowering. It is known that the time for flowering and the sensitivity to cold treatment, in terms of flowering anticipation, varies in numerous hybrids, while no information seems to be available on the influence of hybrids and on the vernalization on the photosynthetic process and primary metabolite profiling. We investigated the influence of two ranunculus hybrids, MDR and MBO, and two preparation procedures of tuberous roots, only rehydration (Control, C) and rehydration followed by vernalization (V), on the photosynthesis and photochemistry of plants grown in a climatic chamber, under a controlled environment. In addition, in MBO plants, in which the vernalization showed the main effects, carbohydrate, amino acid and protein levels were also investigated. In control plants, the response of leaf photosynthesis, to increasing white light, revealed higher photosynthetic activity in MDR than in MBO. The quantum yield of PSII (ϕPSII), electron transport rate (ETR) and non-photochemical quenching (NPQ) did not differ between the two hybrids. The maximal photochemical efficiency (Fv/Fm) was higher in MBO than in MDR and showed a decrease in both hybrids after vernalization. The preparation treatment of propagation material affected the light response of photosynthesis in the two hybrids differently, which increased in plants from vernalized tuberous roots, compared to those from only rehydrated in MBO and decreased in MDR, in accordance to the effects of vernalization observed in leaf photosynthetic pigments. In MBO vernalized tuberous roots, starch was rapidly degraded, and the carbon skeletons used to synthesize amino acids. Control plants of MBO, developed more leaves than those of MDR and a consequent larger plant leaf area. Compared to only rehydration, vernalization of rehydrated tuberous roots increased the plant leaf area in both the hybrids. Compared to the control, vernalized tuberous roots of MBO showed higher concentrations of sucrose and free amino acids, which could act as a long-distance signal promoting floral transition in young leaf primordia.