CsSHMT3 gene enhances the growth and development in cucumber seedlings under salt stress.

Salt stress is one of the major factors limiting plant growth and productivity. Many studies have shown that serine hydroxymethyltransferase (SHMT) gene play an important role in growth, development and stress response in plants. However, to date, there have been few studies on whether SHMT3 can enhance salt tolerance in plants. Therefore, the effects of overexpression or silencing of CsSHMT3 gene on cucumber seedling growth under salt stress were investigated in this study. The results showed that overexpression of CsSHMT3 gene in cucumber seedlings resulted in a significant increase in chlorophyll content, photosynthetic rate and proline (Pro) content, and antioxidant enzyme activity under salt stress condition; whereas the content of malondialdehyde (MDA), superoxide anion (H2O2), hydrogen peroxide (O2·-) and relative conductivity were significantly decreased when CsSHMT3 gene was overexpressed. However, the content of chlorophyll and Pro, photosynthetic rate, and antioxidant enzyme activity of the silenced CsSHMT3 gene lines under salt stress were significantly reduced, while MDA, H2O2, O2·- content and relative conductivity showed higher level in the silenced CsSHMT3 gene lines. It was further found that the expression of stress-related genes SOD, CAT, SOS1, SOS2, NHX, and HKT was significantly up-regulated by overexpressing CsSHMT3 gene in cucumber seedlings; while stress-related gene expression showed significant decrease in silenced CsSHMT3 gene seedlings under salt stress. This suggests that overexpression of CsSHMT3 gene increased the salt tolerance of cucumber seedlings, while silencing of CsSHMT3 gene decreased the salt tolerance. In conclusion, CsSHMT3 gene might positively regulate salt stress tolerance in cucumber and be involved in regulating antioxidant activity, osmotic adjustment, and photosynthesis under salt stress. KEY MESSAGE: CsSHMT3 gene may positively regulate the expression of osmotic system, photosynthesis, antioxidant system and stress-related genes in cucumber.

A tomato NAC transcription factor, SlNAP1, directly regulates gibberellin-dependent fruit ripening.

In tomato (Solanum lycopersicum), the ripening of fruit is regulated by the selective expression of ripening-related genes, and this procedure is controlled by transcription factors (TFs). In the various plant-specific TF families, the no apical meristem (NAM), Arabidopsis thaliana activating factor 1/2 (ATAF1/2), and cup-shaped cotyledon 2 (CUC2; NAC) TF family stands out and plays a significant function in plant physiological activities, such as fruit ripening (FR). Despite the numerous genes of NAC found in the tomato genome, limited information is available on the effects of NAC members on FR, and there is also a lack of studies on their target genes. In this research, we focus on SlNAP1, which is a NAC TF that positively influences the FR of tomato. By employing CRISPR/Cas9 technology, compared with the wild type (WT), we generated slnap1 mutants and observed a delay in the ethylene production and color change of fruits. We employed the yeast one-hybrid (Y1H) and dual-luciferase reporter (DLR) assays to confirm that SlNAP1 directly binds to the promoters of two crucial genes involved in gibberellin (GA) degradation, namely SlGA2ox1 and SlGA2ox5, thus activating their expression. Furthermore, through a yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BIFC) and luciferase (LUC) assays, we established an interaction between SlNAP1 and SlGID1. Hence, our findings suggest that SlNAP1 regulates FR positively by activating the GA degradation genes directly. Additionally, the interaction between SlNAP1 and SlGID1 may play a role in SlNAP1-induced FR. Overall, our study provides important insights into the molecular mechanisms through which NAC TFs regulate tomato FR via the GA pathway.

Hydrogen Sulfide in the Oxidative Stress Response of Plants: Crosstalk with Reactive Oxygen Species.

Growing evidence suggests that exposure of plants to unfavorable environments leads to the accumulation of hydrogen sulfide (H2S) and reactive oxygen species (ROS). H2S interacts with the ROS-mediated oxidative stress response network at multiple levels. Therefore, it is essential to elucidate the mechanisms by which H2S and ROS interact. The molecular mechanism of action by H2S relies on the post-translational modification of the cysteine sulfur group (-SH), known as persulfidation. H2S cannot react directly with -SH, but it can react with oxidized cysteine residues, and this oxidation process is induced by H2O2. Evidently, ROS is involved in the signaling pathway of H2S and plays a significant role. In this review, we summarize the role of H2S-mediated post-translational modification mechanisms in oxidative stress responses. Moreover, the mechanism of interaction between H2S and ROS in the regulation of redox reactions is focused upon, and the positive cooperative role of H2S and ROS is elucidated. Subsequently, based on the existing evidence and clues, we propose some potential problems and new clues to be explored, which are crucial for the development of the crosstalk mechanism of H2S and ROS in plants.

The Crucial Role of SlGSNOR in Regulating Postharvest Tomato Fruit Ripening.

S-nitrosoglutathione reductase (GSNOR) is a well-known regulator in controlling protein S-nitrosylation modification and nitric oxide (NO) homeostasis. Here, a GSNOR inhibitor N6022 and SlGSNOR silencing were applied to investigate the roles of SlGSNOR in tomato fruit postharvest ripening. We found that the application of N6022 and S-nitrosoglutathione (GSNO, a NO donor), and SlGSNOR silencing delayed the transition of fruit skin color by improving total chlorophyll level by 88.57%, 44.78%, and 91.03%, respectively. Meanwhile, total carotenoid and lycopene contents were reduced by these treatments. Concurrently, the activity of chlorophyll biosynthesis enzymes and the expression of related genes were upregulated, and the transcript abundances of total carotenoid bioproduction genes were downregulated, by N6022 and GSNO treatments and SlGSNOR silencing. In addition, fruit softening was postponed by N6022, GSNO, and SlGSNOR silencing, through delaying the decrease of firmness and declining cell wall composition; structure-related enzyme activity; and gene expression levels. Furthermore, N6022, GSNO, and SlGSNOR silencing enhanced the accumulation of titratable acid; ascorbic acid; total phenol; and total flavonoid, but repressed the content of soluble sugar and soluble protein accompanied with the expression pattern changes of nutrition-related genes. In addition, the endogenous NO contents were elevated by 197.55%; 404.59%; and 713.46%, and the endogenous SNOs contents were enhanced by 74.65%; 93.49%; and 94.85%; by N6022 and GSNO treatments and SlGSNOR silencing, respectively. Altogether, these results indicate that SlGSNOR positively promotes tomato postharvest fruit ripening, which may be largely on account of its negative roles in the endogenous NO level.

Genome-Wide Identification and Characterization of Tomato Fatty Acid ß-Oxidase Family Genes KAT and MFP.

Fatty acids and their derivatives play a variety of roles in living organisms. Fatty acids not only store energy but also comprise membrane lipids and act as signaling molecules. There are three main proteins involved in the fatty acid ß-oxidation pathway in plant peroxisomes, including acyl-CoA oxidase (ACX), multifunctional protein (MFP), and 3-ketolipoyl-CoA thiolase (KAT). However, genome-scale analysis of KAT and MFP has not been systemically investigated in tomatoes. Here, we conducted a bioinformatics analysis of KAT and MFP genes in tomatoes. Their physicochemical properties, protein secondary structure, subcellular localization, gene structure, phylogeny, and collinearity were also analyzed. In addition, a conserved motif analysis, an evolutionary pressure selection analysis, a cis-acting element analysis, tissue expression profiling, and a qRT-PCR analysis were conducted within tomato KAT and MFP family members. There are five KAT and four MFP family members in tomatoes, which are randomly distributed on four chromosomes. By analyzing the conserved motifs of tomato KAT and MFP family members, we found that both KAT and MFP members are highly conserved. In addition, the results of the evolutionary pressure selection analysis indicate that the KAT and MFP family members have evolved mainly from purifying selection, which makes them more structurally stable. The results of the cis-acting element analysis show that SlKAT and SlMFP with respect may respond to light, hormones, and adversity stresses. The tissue expression analysis showed that KAT and MFP family members have important roles in regulating the development of floral organs as well as fruit ripening. The qRT-PCR analysis revealed that the expressions of SlKAT and SlMFP genes can be regulated by ABA, MeJA, darkness, NaCl, PEG, UV, cold, heat, and H2O2 treatments. These results provide a basis for the involvement of the SlKAT and SlMFP genes in tomato floral organ development and abiotic stress response, which lay a foundation for future functional study of SlKAT and SlMFP in tomatoes.

SlSERK3B Promotes Tomato Seedling Growth and Development by Regulating Photosynthetic Capacity.

Brassinosteroids (BRs) are a group of polyhydroxylated steroids for plant growth and development, regulating numerous physiological and biochemical processes and participating in multi-pathway signaling in plants. 24-Epibrassinolide (EBR) is the most commonly used BR for the investigation of the effects of exogenous steroidal phytohormones on plant physiology. Although SlSERK3B is considered a gene involved in the brassinosteroid (BR) signaling pathway, its specific role in plant growth and development has not been reported in detail. In this study, tomato (Solanum lycopersicum L.) seedlings treated with 0.05 µmol L-1 EBR showed a significant increase in plant height, stem diameter, and fresh weight, demonstrating that BR promotes the growth of tomato seedlings. EBR treatment increased the expression of the BR receptor gene SlBRI1, the co-receptor gene SlSERK3A and its homologs SlSERK3B, and SlBZR1. The SlSERK3B gene was silenced by TRV-mediated virus-induced gene silencing (VIGS) technology. The results showed that both brassinolide (BL) content and BR synthesis genes were significantly up-regulated in TRV-SlSERK3B-infected seedlings compared to the control seedlings. In contrast, plant height, stem diameter, fresh weight, leaf area and total root length were significantly reduced in silenced plants. These results suggest that silencing SlSERK3B may affect BR synthesis and signaling, thereby affecting the growth of tomato seedlings. Furthermore, the photosynthetic capacity of TRV-SlSERK3B-infected tomato seedlings was reduced, accompanied by decreased photosynthetic pigment content chlorophyll fluorescence, and photosynthesis parameters. The expression levels of chlorophyll-degrading genes were significantly up-regulated, and carotenoid-synthesising genes were significantly down-regulated in TRV-SlSERK3B-infected seedlings. In conclusion, silencing of SlSERK3B inhibited BR signaling and reduced photosynthesis in tomato seedlings, and this correlation suggests that SlSERK3B may be related to BR signaling and photosynthesis enhancement.

The Characteristics and Expression Analysis of the Tomato SlRBOH Gene Family under Exogenous Phytohormone Treatments and Abiotic Stresses.

Respiratory burst oxidase homologs (RBOHs), also known as NADPH oxidases, contribute significantly to the production of ROS in plants, alongside other major sources such as photosynthesis and electron transport in chloroplasts. It has been shown that plant RBOHs play an active role in plant adversity response and electron transport. However, the phylogenetic analysis and characterization of the SlRBOH gene family in tomatoes have not been systematically studied. This study identified 11 SlRBOH genes in the tomato genome using a genome-wide search approach. The physicochemical properties, chromosomal localization, subcellular localization, secondary structure, conserved motifs, gene structure, phylogenetics, collinear relationships, cis-acting elements, evolutionary selection pressures, tissue expressions, and expression patterns under exogenous phytohormones (ABA and MeJA) and different abiotic stresses were also analyzed. We found that the SlRBOHs are distributed across seven chromosomes, collinearity reflecting their evolutionary relationships with corresponding genes in Arabidopsis thaliana and rice. Additionally, all the SlRBOH members have five conserved domains and 10 conserved motifs and have similar gene structures. In addition, the results of an evolutionary selection pressure analysis showed that SlRBOH family members evolved mainly by purifying selection, making them more structurally stable. Cis-acting element analyses showed that SlRBOHs were responsive to light, hormone, and abiotic stresses. Tissue expression analysis showed that SlRBOH family members were expressed in all tissues of tomato to varying degrees, and most of the SlRBOHs with the strongest expression were found in the roots. In addition, the expressions of tomato SlRBOH genes were changed by ABA, MeJA, dark period extension, NaCl, PEG, UV, cold, heat, and H2O2 treatments. Specifically, SlRBOH4 was highly expressed under NaCl, PEG, heat, and UV treatments, while SlRBOH2 was highly expressed under cold stress. These results provide a basis for further studies on the function of SlRBOHs in tomato.

Brassinosteroids is involved in methane-induced adventitious root formation via inducing cell wall relaxation in marigold.

BACKGROUND: Methane (CH4) and brassinosteroids (BRs) are important signaling molecules involved in a variety of biological processes in plants. RESULTS: Here, marigold (Tagetes erecta L. 'Marvel') was used to investigate the role and relationship between CH4 and BRs during adventitious root (AR) formation. The results showed a dose-dependent effect of CH4 and BRs on rooting, with the greatest biological effects of methane-rich water (MRW, CH4 donor) and 2,4-epibrassinolide (EBL) at 20% and 1 µmol L- 1, respectively. The positive effect of MRW on AR formation was blocked by brassinoazole (Brz, a synthetic inhibitor of EBL), indicating that BRs might be involved in MRW-regulated AR formation. MRW promoted EBL accumulation during rooting by up-regulating the content of campestanol (CN), cathasterone (CT), and castasterone (CS) and the activity of Steroid 5α-reductase (DET2), 22α-hydroxylase (DWF4), and BR-6-oxidase (BR6ox), indicating that CH4 could induce endogenous brassinolide (BR) production during rooting. Further results showed that MRW and EBL significantly down-regulated the content of cellulose, hemicellulose and lignin during rooting and significantly up-regulated the hydrolase activity, i.e. cmcase, xylanase and laccase. In addition, MRW and EBL also significantly promoted the activity of two major cell wall relaxing factors, xyloglucan endotransglucosylase/hydrolase (XTH) and peroxidase, which in turn promoted AR formation. While, Brz inhibited the role of MRW on these substances. CONCLUSIONS: BR might be involved in CH4-promoted AR formation by increasing cell wall relaxation.

Carbon monoxide/heme oxygenase system in plant: Roles in abiotic stress response and crosstalk with other signals molecules.

Carbon monoxide (CO) has been recognized as a crucial gasotransmitter mainly produced by heme oxygenase (HO)-catalyzed heme degradation in plant. Recent studies have shown that CO plays an important role in regulating growth and development of plant, as well as and responding to a variety of abiotic stresses. Meanwhile, many studies have reported on CO working in combination with other signal molecules to mitigate abiotic stress. Here, we presented a comprehensive overview of recent developments in which CO reduces plant damage caused by abiotic stresses. The regulation of antioxidant system, photosynthetic system, ion balance and transport are the main mechanisms of CO-alleviated abiotic stress. We also proposed and discussed the relationship between CO and other signal molecules, including nitric oxide (NO), hydrogen sulfide (H2S), hydrogen gas (H2), abscisic acid (ABA), indole 3-acetic acid (IAA), gibberellin (GA), cytokine (CTK), salicylic acid (SA), jasmonic acid (JA), hydrogen peroxide (H2O2) and calcium ion (Ca2+). Furthermore, the important role of HO genes in alleviating abiotic stress was also discussed. We proposed promising and new research directions for the study of plant CO, which can provide further insights on the role of CO in plant growth and development under abiotic stress.

Advances in Nitric Oxide Signalling and Metabolism in Plants.

More than 15,000 scientific articles published since the late 1950s related to RNS action or detection in various plant materials are listed in the Web of Science database [...].

The Role of Light-Regulated Auxin Signaling in Root Development.

The root is an important organ for obtaining nutrients and absorbing water and carbohydrates, and it depends on various endogenous and external environmental stimulations such as light, temperature, water, plant hormones, and metabolic constituents. Auxin, as an essential plant hormone, can mediate rooting under different light treatments. Therefore, this review focuses on summarizing the functions and mechanisms of light-regulated auxin signaling in root development. Some light-response components such as phytochromes (PHYs), cryptochromes (CRYs), phototropins (PHOTs), phytochrome-interacting factors (PIFs) and constitutive photo-morphorgenic 1 (COP1) regulate root development. Moreover, light mediates the primary root, lateral root, adventitious root, root hair, rhizoid, and seminal and crown root development via the auxin signaling transduction pathway. Additionally, the effect of light through the auxin signal on root negative phototropism, gravitropism, root greening and the root branching of plants is also illustrated. The review also summarizes diverse light target genes in response to auxin signaling during rooting. We conclude that the mechanism of light-mediated root development via auxin signaling is complex, and it mainly concerns in the differences in plant species, such as barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.), changes of transcript levels and endogenous IAA content. Hence, the effect of light-involved auxin signaling on root growth and development is definitely a hot issue to explore in the horticultural studies now and in the future.

Characterization of the FLA Gene Family in Tomato (Solanum lycopersicum L.) and the Expression Analysis of SlFLAs in Response to Hormone and Abiotic Stresses.

Fasciclin-like arabinogalactan proteins (FLAs), a subclass of arabinogalactan proteins (AGPs), participate in mediating plant growth, development, and response to abiotic stress. However, the characterization and function of FLAs in tomato are currently unknown. In this study, members of the tomato FLA family are characterized and analyzed in relation to their response to phytohormonal and abiotic stresses. The results show that a total of 24 FLA members were characterized in tomato. The structural domain analysis showed that these members have a high protein similarity. The expression profiles of different tissues indicated that the genes of most members of the tomato FLA gene family are highly expressed in roots, but to a lower extent in fruits. qRT-PCR analysis revealed that all 24 tomato FLA genes are responsive to ABA and MeJA. SlFLAs showed a positive response to salt and cold stress. SlFLA1, SlFLA12, and SlFLA14 are significantly induced under darkness. SlFLA1 and SlFLA3 are significantly induced under drought stress. This study provides a basis for a further understanding of the role of tomato FLA homologous genes in plant response to abiotic stress and lays the foundation for further research on the function of FLAs in tomato.

Comprehensive evaluation on effect of planting and breeding waste composts on the yield, nutrient utilization, and soil environment of baby cabbage.

Treatment of the planting and breeding waste is becoming a big issue due to their significant quantities. Composting could be an effective alternative for planting and breeding waste management which could be used as fertilizer. The purpose of this research was to evaluate the effect of planting and breeding waste on baby cabbage growth and soil properties, to establish a suitable agricultural cycle model for semi-arid area in central Gansu Province. The planting and breeding wastes [sheep manure (SM), tail vegetable (TV), cow manure (CM), mushroom residue (MR) and corn straw (CS)] were used as the raw materials in this study, which were designed 8 compost formulas for composting fermentation. With no fertilization (CK1) and local commercial organic fertilizer (CK2) as the control, the comprehensive evaluation of planting and breeding waste composts on the yield of baby cabbage, fertilizer utilization rate, soil physical and chemical properties and microbial diversity were studied to select the best compost formula suitable for the growth of baby cabbage. And the material flow and energy flow analysis of the circulation model established by the formula were carried out. The results showed that the biological yield and economic yield of baby cabbage, absorption and recycling utilization of total phosphorus (TP) and total potassium (TK) reached the maximum under the formula of SM: TV: MR: CS = 6:2:1:1. Compared with CK2, the formula of SM: TV: MR: CS = 6:2:1:1 significantly increased the richness of soil bacteria and beneficial bacteria Proteobacteria, and decreased the relative abundance of harmful bacteria Olpidiomycota. Principal component analysis showed the comprehensive score of SM: TV: MR: CS = 6:2:1:1 was the best organic compost formula suitable for producing high-quality and high-yield baby cabbage and improving soil environment. Therefore, this formula can be used as a reference organic fertilizer formula for field cultivation of baby cabbage.

Heme is involved in the exogenous ALA-promoted growth and antioxidant defense system of cucumber seedlings under salt stress.

A biosynthetic precursor of tetrapyrrol, 5-aminolevulinic acid (ALA), is widely used in agricultural production, as an exogenous regulatory substance that effectively regulates plant growth. Previous studies have shown that heme and chlorophyll accumulate in plants under salt stress, when treated with exogenous ALA. In this study, we explored the regulatory role of heme in plants, by spraying 25 mg L-1 ALA onto the leaves of cucumber seedlings treated with heme synthesis inhibitor (2,2'-dipyridyl, DPD) and heme scavenger (hemopexin, Hx), under 50 mmol L-1 NaCl stress. The results showed that NaCl alone and DPD + Hx treatments to cucumber seedlings subjected to salt stress adversely affected their growth, by decreasing biomass accumulation, root activity, and root morphology. In addition, these treatments induced an increase in membrane lipid oxidation, as well as enhancement of anti-oxidase activities, proline content, and glutamate betaine. However, exogenous ALA application increased the plant growth and root architecture indices under NaCl stress, owing to a lack of heme in the seedlings. In addition, cucumber seedlings treated with DPD and Hx showed inhibition of growth under salt stress, but exogenous ALA effectively improved cucumber seedling growth as well as the physiological characteristics; moreover, the regulation of ALA in plants was weakened when heme synthesis was inhibited. Heme biosynthesis and metabolism genes, HEMH and HO1, which are involved in the ALA metabolic pathway, were upregulated under salinity conditions, when ferrochelatase activity was inhibited. Application of exogenous ALA increased the heme content in the leaves. Thus, exogenous ALA may supplement the substrates for heme synthesis. These results indicated that heme plays a vital role in the response of plants to salinity stress. In conclusion, heme is involved in ALA-mediated alleviation of damage caused to cucumber seedlings and acts as a positive regulator of plant adaption.

Nitric oxide alleviates salt stress through protein S-nitrosylation and transcriptional regulation in tomato seedlings.

MAIN CONCLUSION: NO enhances the resistance of tomato seedlings to salt stress through protein S-nitrosylation and transcriptional regulation, which involves the regulation of MAPK signaling and carbohydrate metabolism. Nitric oxide (NO) regulates various physiological and biochemical processes and stress responses in plants. We found that S-nitrosoglutathione (GSNO) treatment significantly promoted the growth of tomato seedling under NaCl stress, indicating that NO plays a positive role in salt stress resistance. Moreover, GSNO pretreatment resulted in an increase of endogenous NO level, S-nitrosothiol (SNO) content, S-nitrosoglutathione reductase (GSNOR) activity and GSNOR expression under salt stress, implicating that S-nitrosylation might be involved in NO-alleviating salt stress. To further explore whether S-nitrosylation is a key molecular mechanism of NO-alleviating salt stress, the biotin-switch technique and liquid chromatography/mass spectrometry/mass spectrometry (LC-MS/MS) were conducted. A total of 1054 putative S-nitrosylated proteins have been identified, which were mainly enriched in chloroplast, cytoplasm and mitochondrion. Among them, 15 and 22 S-nitrosylated proteins were involved in mitogen-activated protein kinase (MAPK) signal transduction and carbohydrate metabolism, respectively. In MAPK signaling, various S-nitrosylated proteins, SAM1, SAM3, SAM, PP2C and SnRK, were down-regulated and MAPK, MAPKK and MAPKK5 were up-regulated at the transcriptional level by GSNO treatment under salt stress compared to NaCl treatment alone. The GSNO pretreatment could reduce ethylene production and ABA content under NaCl stress. In addition, the activities of enzyme identified in carbohydrate metabolism, their expression at the transcriptional level and the metabolite content were up-regulated by GSNO supplication under salt stress, resulting in the activation of glycolysis and tricarboxylic acid cycle (TCA) cycles. Thus, these results demonstrated that NO might beneficially regulate MAPK signaling at transcriptional levels and activate carbohydrate metabolism at the post-translational and transcriptional level, protecting seedlings from energy deficiency and salinity, thereby alleviating salt stress-induced damage in tomato seedlings. It provides initial insights into the regulatory mechanisms of NO in response to salt stress.

DNA methylation in tomato fruit ripening.

Fleshy fruit, the most economical and nutritional value unique to flowering plants, is an important part of our daily diet. Previous studies have shown that fruit ripening is regulated by transcription factors and the plant hormone ethylene, but recent research has also shown that epigenetics also plays an essential role, especially DNA methylation. DNA methylation is the process of transferring -CH3 to the fifth carbon of cytosine residues under the action of methyltransferase to form 5-methylcytosine (5-mC). So far, most works have been focused on tomato. Tomato ripening is dynamically regulated by DNA methylation and demethylation, but the understanding of this mechanism is still in its infancy. The dysfunction of a DNA demethylase, DEMETER-like DNA demethylases 2 (DML2), prevents the ripening of tomato fruits, but immature fruits ripen prematurely under the action of DNA methylation inhibitors. Additionally, studies have shown that the relationship between fruit quality and DNA methylation is not linear, but the specific molecular mechanism is still unclear. Here, we review the recent advances in the role of DNA methylation in tomato fruit ripening, the interaction of ripening transcription factors and DNA methylation, and its effects on quality. Then, a number of questions for future research of DNA methylation regulation in tomato fruit ripening is proposed.

Comprehensive transcriptome analysis unravels the crucial genes during adventitious root development induced by carbon monoxide in Cucumis sativus L.

BACKGROUND: Carbon monoxide (CO) has been reported to be participated in adventitious rooting. However, knowledge about the interrelationship between CO and phytohormones during rooting is obscure. The molecular mechanism of CO-induced rooting is currently unclear. METHODS AND RESULTS: The roles of CO in adventitious rooting in Cucumis sativus L. at the transcriptional level were investigated. The results show that 10 µM hematin (a CO donor) has a significant positive effect on adventitious rooting in cucumber. A total of 1792 differentially expressed genes (DEGs; 1103 up-regulated and 689 down-regulated) were identified in hematin treatment by RNA sequencing analysis. There were 37, 18 and 19 DEGs significantly enriched in plant hormone signal transduction, sucrose and starch metabolism, and phenylalanine metabolism, respectively. Both transcriptome and real-time quantitative PCR results showed that the expressions of AUX22D, IAA6, SAUR21, SAUR24, GH3.5, CYCD3-3, TIFY10a, TIFY10A and TIF9 promoted the accumulation of IAA, BR, JA and SA in plant hormone signal transduction. The up-regulation of HK3, TPPF, otsB, TPS7, TPS9 and the down-regulation of AGPS1, AGPS3 increased the content of starch and total sugar by mediating the activity of some critical enzymes, including HK, TPS, TPP and AGP. PER47, PER61, PER24, PER66, PER4 and CCR2 increased the lignin content. CONCLUSION: Our results suggest that CO could promote the accumulation of plant hormones, starch, sugar and lignin during adventitious rooting by regulating the expression of some related genes, including AUX22D, IAA6, SAUR21, SAUR24, GH3.5, CYCD3-3, TIFY10a, TIFY10A, TIF9 HK3, otsB, TPS7, TPS9, AGPS1, AGPS3, PER47, PER61, PER24, PER66, PER4, and CCR2. Thus, we provides an interesting candidate gene list for further studies on the molecular mechanisms of adventitious rooting.

Strigolactone is involved in nitric oxide-enhanced the salt resistance in tomato seedlings.

Both strigolactones (SLs) and nitric oxide (NO) are regulatory signals with diverse roles during stress responses. At present, the interaction and mechanism of SLs and NO in tomato salt tolerance remain unclear. In the current study, tomato 'Micro-Tom' was used to study the roles and interactions of SLs and NO in salinity stress tolerance. The results show that 15 µM SLs synthetic analogs GR24 and 10 µM NO donor S-nitrosoglutathione (GSNO) promoted seedling growth under salt stress. TIS108 (an inhibitor of strigolactone synthesis) suppressed the positive roles of NO in tomato growth under salt stress, indicating that endogenous SLs might be involved in NO-induced salt response in tomato seedlings. Meanwhile, under salt stress, GSNO or GR24 treatment induced the increase of endogenous SLs content in tomato seedlings. Moreover, GR24 or GSNO treatment effectively increased the content of chlorophyll, carotenoids and ascorbic acid (ASA), and enhanced the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase), glutathione reductase (GR) and cleavage dioxygenase (CCD) enzyme. Additionally, GSNO or GR24 treatment also up-regulated the expression of SLs synthesis genes (SlCCD7, SlCCD8, SlD27 and SlMAX1) and its signal transduction genes (SlD14 and SlMAX2) in tomato seedlings under salt stress. While, a strigolactone synthesis inhibitor TIS108 blocked the increase of endogenous SLs, chlorophyll, carotenoids and ASA content, and antioxidant enzyme, GR, CCD enzyme activity and SLs-related gene expression levels induced by GSNO. Thus, SLs may play an important role in NO-enhanced salinity tolerance in tomato seedlings by increasing photosynthetic pigment content, enhancing antioxidant capacity and improving endogenous SLs synthesis.

Mitogen-Activated Protein Kinase Is Involved in Salt Stress Response in Tomato (Solanum lycopersicum) Seedlings.

Salt stress impairs plant growth and development, thereby causing low yield and inferior quality of crops. In this study, tomato (Solanum lycopersicum L. 'Micro-Tom') seedlings treated with different concentrations of sodium chloride (NaCl) were investigated in terms of decreased plant height, stem diameter, dry weight, fresh weight, leaves relative water content and root activity. To reveal the response mechanism of tomato seedlings to salt stress, the transcriptome of tomato leaves was conducted. A total of 6589 differentially expressed genes (DEGs) were identified and classified into different metabolic pathways, especially photosynthesis, carbon metabolism, biosynthesis of amino acids and mitogen-activated protein kinase (MAPK) signaling pathway. Of these, approximately 42 DEGs were enriched in the MAPK signaling pathway, most of which mainly included plant hormone, hydrogen peroxide (H2O2), wounding and pathogen infection signaling pathways. To further explore the roles of MAPK under salt stress, MAPK phosphorylation inhibitor SB203580 (SB) was applied. We found that SB further decreased endogenous jasmonic acid, abscisic acid and ethylene levels under salt stress condition. Additionally, in comparison with NaCl treatment alone, SB + NaCl treatment reduced the content of O2- and H2O2 and the activities of antioxidant enzyme and downregulated the expression levels of genes related to pathogen infection. Together, the results revealed that MAPK might be involved in the salinity response of tomato seedlings by regulating hormone balance, ROS metabolism, antioxidant capacity and plant immunity.

Role of Nitric Oxide in Postharvest Senescence of Fruits.

Nitric oxide (NO) acts as a gaseous signalling molecule and is considered to be a key regulator in the postharvest storage of fruits. Postharvest senescence is one of the most serious threats affecting the usage and economic value of fruits. Most recent studies have found that exogenous NO application can effectively improve the quality and prolong the shelf life of fruit postharvest by inhibiting postharvest diseases and alleviating chilling injury. Understanding the roles of NO is essential to elucidating how NO activates the appropriate set of responses to postharvest senescence. Here, we concluded that exogenous NO treatment alleviated senescence in postharvest fruit and attributed this to the following factors: (1) ethylene biosynthesis, (2) the antioxidant system, (3) polyamine metabolism and γ-aminobutyric acid (GABA) shunting, (4) cell wall metabolism, (5) sugar metabolism, (6) energy metabolism, (7) the CRT/DRE-binding factor (CBF) pathway and (8) S-nitrosylation. Moreover, crosstalk between NO and hydrogen sulfide (H2S), hydrogen peroxide (H2O2), oxalic acid (OA), arginine (Arg), GATA or plant hormone abscisic acid (ABA), melatonin (MT), and methyl jasmonate (MeJA), along with the regulation of key genes, were found to be very important in responses to postharvest senescence. In this study, we focus on the recent knowledge concerning the alleviative effect of NO on postharvest senescence, covering ethylene biosynthesis, the antioxidant system and related gene and protein expression.