Ethylene Treatment Research Articles

Isolation and functional characterization of the mitogen-activated protein kinase kinase gene MAPKK1 from Panax notoginseng

Mitogen-activated protein kinase (MAPK) cascades are important signal transduction mechanisms that connect plant cellular and nuclear responses, which play key roles in plant development and stress responses. Here, the novel MAPK kinase (MAPKK) gene MAPKK1 was isolated from Panax notoginseng (Burk) F.H. Chen. Exogenous methyl jasmonate (MeJA), salicylic acid (SA), ethylene, and hydrogen peroxide treatments induced the transcription level of PnMAPKK1 in P. notoginseng roots. Additionally, PnMAPKK1 expression actively responded to Fusarium solani infection, a major causal agent of P. notoginseng root rot disease. The PnMAPKK1 gene was further fused with the green fluorescent protein gene in a plant expression vector and transformed into onion (Allium cepa) epidermal cells. Laser scanning confocal microscopy confirmed that the PnMAPKK1 protein localized in the cytoplasm. In addition, the plant overexpression vector pCAMBIA2300s-PnMAPKK1 was constructed and transformed into tobacco (Nicotiana tabacum L. cv. Xanthi). The PnMAPKK1 transgenic tobacco lines showed much stronger resistance levels to F. solani infection than the wild type. Moreover, the JA and SA contents in the PnMAPKK1 transgenic tobacco lines were significantly higher than those in wild type during F. solani infection. The up-regulation of several marker genes (PAL4, PR1c, WRKY1, Defensin, and LOC4) involved in JA and SA signaling was correlated with the overexpression of PnMAPKK1 in tobacco. Thus, the PnMAPKK1 gene is a positive regulator of defense responses to F. solani in P. notoginseng.

GhVLN4 is involved in multiple stress responses and required for resistance to Verticillium wilt

As structural and signaling platform in plant cell, the actin cytoskeleton is regulated by diverse actin binding proteins (ABPs). Villins are one type of major ABPs responsible for microfilament bundling, which have proved to play important roles in plant growth and development. However, the function of villins in stress tolerance is poorly understood. Here, we report the function of cotton GhVLN4 in Verticillium wilt resistance and abiotic stress tolerance. The expression of GhVLN4 was up-regulated by gibberellin, ethylene, ABA, salicylic acid, jasmonate, NaCl, PEG, and Verticillium dahliae treatment, suggesting the involvement of GhVLN4 in multiple stress and hormone responses and signaling. Virus-induced gene silencing GhVLN4 made cotton more susceptible to V. dahliae characterized by the preferential colonization and rapid growth of the fungus in both phloem and xylem of the infected stems. Arabidopsis overexpressing GhVLN4 exhibited higher resistance to V. dahliae, salt and drought than the wild-type plants. The enhanced resistance to V. dahliae is likely related to the upregulated components in SA signaling pathway; the improved tolerance to salt and drought is characterized by upregulation of the components both in ABA- related and ABA-independent signal pathways, along with altered stomatal aperture under drought. Our findings demonstrate that GhVLN4 may play important roles in regulating plant tolerance to both biotic and abiotic stresses.

Involvement of CsERF2 in leaf variegation of Cymbidium sinense \u2018Dharma\u2019

Main conclusionCsERF2, an ethylene response factor, plays a role in leaf variegation.Leaf variegation is a main ornamental characteristic in Cymbidium sinense (C. sinense). However, the mechanisms of leaf color variegation remain largely unclear. In the present study, we analyzed the cytological and physiological features, as well as molecular analyses of leaves from wild-type (WT) and leaf variegation mutants of Cymbidium sinense ‘Dharma’. Chloroplasts with typical and functional structures were discovered in WT and green sectors of the mutants leaves (MG), but not in yellow sectors of the mutant leaves (MY). The activities of key enzymes involved in chlorophyll (Chl) degradation and their substrate contents were significantly increased in MY. Genes related to Chl degradation also showed a significant up-regulation in MY. Transcriptomic analysis showed that the expression of all identified ethylene response factors (ERFs) was significantly up-regulated, and the 1-aminocyclopropane-1-carboxylic acid (ACC) content in MY was significantly higher compared with MG. QRT-PCR analysis validated that the expression levels of genes related to Chl degradation could be positively affected by ethylene (ETH) treatment. Stable overexpression of CsERF2 in Nicotiana tabacum (N. tabacum) led to a decrease in Chl content and abnormal chloroplast. Transcriptomic analysis and qRT-PCR results showed that the KEGG pathway related to chloroplast development and function showed significant change in transgenic N. tabacum. Therefore, the leaf color formation of C. sinense was greatly affected by chloroplast development and Chl metabolism. CsERF2 played an important role in leaf variegation of C. sinense.

Ethylene regulates sulfur acquisition by regulating the expression of sulfate transporter genes in oilseed rape.

To manage nutrient deficiencies, plants develop both morphological and physiological responses. The studies on the regulation of these responses are limited; however, certain hormones and signaling components have been largely implicated. Several studies depicted ethylene as a regulator of the response of some nutrient deficiencies like iron, phosphorous and potassium. The present study focused on the response of sulfur in the presence and absence of ethylene. The experiments were performed in hydroponic nutrient media, using oilseed rape grown with or without sulfur deficiency and ethylene treatments for 10 days. The ACC oxidase and ACC synthase were observed significantly reduced in sulfur-deficient plants treated with ethylene compared to control. The biomass and photosynthetic parameters, including the expression of multicomplex thylakoidal proteins showed a significant increase in sulfur deficient plants supplemented with ethylene. The enzymes related to sulfur regulation such as sulfate adenyltransferase, glutamine synthetase and O-acetylserine (thiol)lyase also showed similar results as shown by the morphological data. The relative expression of the sulfur transporter genes BnSultr1, 1, BnSultr1, 2, BnSultr4,1, BnSultr 4,2, ATP sulfurylase and OASTL increased in sulfur-deficient plants, whereas their expression decreased when ethylene was given to the plants. Fe and S nutritional correlations are already known; therefore, Fe-transporters like IRT1 and FRO1 were also evaluated, and similar results as for the sulfur transporter genes were observed. The overall results indicated that ethylene regulates sulfur acquisition by regulating the expression of sulfur transporter genes in oilseed rape (Brassica napus).

Identification and Characterization of Glycoproteins and Their Responsive Patterns upon Ethylene Stimulation in the Rubber Latex.

Natural rubber is an important industrial material, which is obtained from the only commercially cultivated rubber tree, Hevea brasiliensis. In rubber latex production, ethylene has been extensively used as a stimulant. Recent research showed that post-translational modifications (PTMs) of latex proteins, such as phosphorylation, glycosylation and ubiquitination, are crucial in natural rubber biosynthesis. In this study, comparative proteomics was performed to identify the glycosylated proteins in rubber latex treated with ethylene for different days. Combined with Pro-Q Glycoprotein gel staining and mass spectrometry techniques, we provided the first visual profiling of glycoproteomics of rubber latex and finally identified 144 glycosylated protein species, including 65 differentially accumulated proteins (DAPs) after treating with ethylene for three and/or five days. Gene Ontology (GO) functional annotation showed that these ethylene-responsive glycoproteins are mainly involved in cell parts, membrane components and metabolism. Pathway analysis demonstrated that these glycosylated rubber latex proteins are mainly involved in carbohydrate metabolism, energy metabolism, degradation function and cellular processes in rubber latex metabolism. Protein–protein interaction analysis revealed that these DAPs are mainly centered on acetyl-CoA acetyltransferase and hydroxymethylglutaryl-CoA synthase (HMGS) in the mevalonate pathway for natural rubber biosynthesis. In our glycoproteomics, three protein isoforms of HMGS2 were identified from rubber latex, and only one HMGS2 isoform was sharply increased in rubber latex by ethylene treatment for five days. Furthermore, the HbHMGS2 gene was over-expressed in a model rubber-producing grass Taraxacum Kok-saghyz and rubber content in the roots of transgenic rubber grass was significantly increased over that in the wild type plant, indicating HMGS2 is the key component for natural rubber production.

The complexity of folate polyglutamylation in plants: Postharvest ripening and ethylene modulate polyglutamylated profiles in climacteric fruits plus systematic analysis of the glutamyl tail-editing enzymes

Folate derivatives exist in nature in a variety of polyglutamyl forms (Glun); the glutamyl tail is added to the folate molecule by folylpolyglutamate synthetase (FPGS), and removed by gamma-glutamyl hydrolase (GGH) isoforms in several compartments within the cell. Folate polyglutamylation affects the use of the folate cofactors and their transport in organisms, also impacting their bioavailability as vitamins in mammals; however, little is known about its regulation in plants. We explored the possible effect of genetic, developmental, and environmental factors on the Glun extent of the most prevalent folate in plants, 5-CH3-THF. We chose ripening and ethylene treatment in climacteric fruits, to assess developmental and environmental factors. Postharvest ripening increased short Glun tails, and ethylene gassing affected negatively long Glun tails. To evaluate genetic factors, we retrieved and compared the deduced FPGS and GGH sequences from 27 plants with known Glun profile and attempted to correlate their phylogenetic relation, number of isoforms, predicted localization, and primary sequence with the Glun profiles generated and gathered by this study. GGH sequences were quite conserved among plants, while FPGS diverged more. We postulate that the very long Glun tail found only in papaya is the result of very particular changes in one of the FPGS’s primary structure.

Ethylene functions as a suppressor of volatile production in rice.

We examined the role of ethylene in the production of rice (Oryza sativa) volatile organic compounds (VOCs), which act as indirect defense signals against herbivores in tritrophic interactions. Rice plants were exposed to exogenous ethylene (1 ppm) after simulated herbivory, which consisted of mechanical wounding supplemented with oral secretions (WOS) from the generalist herbivore larva Mythimna loreyi. Ethylene treatment highly suppressed VOCs in WOS-treated rice leaves, which was further corroborated by the reduced transcript levels of major VOC biosynthesis genes in ethylene-treated rice. In contrast, the accumulation of jasmonates (JA), known to control VOCs in higher plants, and transcript levels of primary JA response genes, including OsMYC2, were not largely affected by ethylene application. At the functional level, flooding is known to promote internode elongation in young rice via ethylene signaling. Consistent with the negative role of ethylene on VOC genes, the accumulation of VOCs in water-submerged rice leaves was suppressed. Furthermore, in mature rice plants, which naturally produce less volatiles, VOCs could be rescued by the application of the ethylene perception inhibitor 1-methylcyclopropene. Our data suggest that ethylene acts as an endogenous suppressor of VOCs in rice plants during development and under stress.

Ethylene Enhances Seed Germination and Seedling Growth Under Salinity by Reducing Oxidative Stress and Promoting Chlorophyll Content via ETR2 Pathway.

Alfalfa (Medicago sativa L.) is an important forage, and salinity is a major stress factor on its yield. In this study, we show that osmotic stress retards alfalfa seedling growth, while ionic/oxidative stress reduces its seed germination. Ethylene treatment can recover the germination rate of alfalfa seeds under salt stress, while ethylene inhibitor silver thiosulfate exacerbates salt effects. ETH reduces the accumulation of MDA and H2O2 and increases POD activity. ETH and ACC improve the salt tolerance of alfalfa by increasing proline content under salt stress. In contrast, STS inhibits alfalfa seed germination by reducing POD activity. NaCl treatment reduces chlorophyll content in alfalfa leaves, while ETH and ACC can increase the chlorophyll content and promote seedling growth. ETH promotes the growth of alfalfa in saline condition by reducing the expression of MsACO and MsERF8 genes, while increases its germination rate by upregulating MsERF11 gene. Silencing of MsETR2, a putative ethylene receptor gene in alfalfa, abolishes ethylene triggered tolerance to salt stress. In summary, we show that ethylene improves salt tolerance in alfalfa via MsETR2 dependent manner, and we also analyze the regulatory mechanism of ethylene during germination of alfalfa seeds under salt stress.

Transcriptome and phytohormone changes associated with ethylene-induced onion bulb dormancy.

Control of dormancy and sprouting in onion bulbs is commercially important for postharvest management. Although ethylene application is sometimes used to extend dormancy, the underlying mechanisms regulating dormancy transition remain unclear. Since the sprout leaves emerge from the bulb baseplate, we used this tissue to assess the impact of ethylene treatment and storage time on the hormone profile and the transcriptome. Reads from 30 libraries were assembled and annotated, with 94,840 unigenes retained after filtering. The de novo transcriptome assembly was of high quality and continuity (N50: 1809 bp, GC content: 36.21 %), and was used to analyse differential expression and Gene Onotologies. Across two years, applied ethylene resulted in delayed dormancy break and reduced post-dormancy sprout vigour. Ethylene supplementation enhanced endogenous ethylene production and caused a transient climacteric-like increase in respiration. Significant changes in hormone and associated transcript profiles occurred through storage and in response to ethylene. In particular, abscisic acid (ABA) and its metabolite phaseic acid (PA) increased under ethylene during the longer dormancy period; however, cytokinin increases observed during storage appeared largely independent of ethylene treatment. Several hormone-related transcripts showed differential expression over time and/or in response to ethylene. Expression of ethylene biosynthesis (ACO), receptor (EIN4) and transcription factor (EIL3) genes were modified by ethylene, as were ABA biosynthesis genes such NCED, and cytokinin biosynthesis genes such as LOG and CKX. We conclude that ethylene substantially modifies expression of genes in several phytohormone pathways, and some of these changes may underlie the dormancy-extending effects of exogenous ethylene.

Removal of dilute ethylene using repetitive cycles of adsorption and plasma-catalytic oxidation over Pd/ZSM-5 catalyst

Ethylene removal was investigated using a reactor system combining plasma and a catalyst (Pd/ZSM-5). The catalyst could adsorb ethylene effectively even under harsh conditions of 100% humidity and 10 000 ppm CO2. The air in a 1 m3 container, which was prepared to imitate agricultural storage, was circulated through the reactor. The process of ethylene treatment consists of one cycle comprising adsorption, plasma-catalyst oxidation, and desorption, and this cycle is repeated until the ethylene is completely removed. Among the variables such as initial concentration, amount of catalyst, voltage, adsorption time, and flow rate of the circulating gas, the most influential were the flow rate and the catalyst amount. The lower the initial ethylene concentration is, the less time required for complete removal, although the percent removal was not largely affected by the initial concentration (20–200 ppm). The ethylene removal was improved by injecting 20 ppm ozone into the container once per cycle. In the absence of ozone, using only the plasma-catalytic reactor, it took 20 h for complete removal, whereas all ethylene was removed in about 8 h in the presence of ozone. A mass balance model could provide a good prediction of the temporal variations of ethylene concentration. The long-term storage stability of a Fuji apple in the container was tested for 40 d. A comparison of the control group with the group subjected to ethylene processing revealed that the ethylene concentrations were significantly different from each other, indicating the efficiency of the plasma-catalyst system. After 40 d of storage, the hardness and sugar content were higher in the group from which ethylene was removed than in the control group, and the acidity was higher in the control group. Furthermore, after 40 d, the control group showed a decay rate of 10%, whereas that of the group that underwent ethylene processing was only 1%.

Study of Parthenocarpy in Three Kiwifruit Commercial Cultivars

ABSTRACT To examine parthenocarpy in commercial kiwifruit cultivars in Japan, ‘Rainbow Red’, ‘Kaimitsu’, and ‘Hayward’ cultivars were subjected to four treatments: 1) pistil removal just before flowering; 2) pistil removal just before flowering and soaking with 10 ppm N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU); 3) soaking with 10 ppm CPPU and natural pollination; and 4) artificial dust pollination. The percentage of fruit borne in the pistil removal treatment groups was 0% in ‘Rainbow Red’ and ‘Hayward’, and was 56% in ‘Kaimitsu’. Although 72% had fallen, the fruit borne in ‘Kaimitsu’ was harvestable. CPPU treatment induced parthenocarpy in the three kiwifruit cultivars. There were no viable seeds in the groups with pistil removal, regardless of treatment with or without CPPU. CPPU treatment also promoted fruit maturity at harvesting time in ‘Rainbow Red’ and ‘Kaimitsu’. In ‘Kaimitsu’, parthenocarpic fruits without CPPU treatment were nearly as ripe as pollinated fruits without CPPU treatment at harvest time. After ethylene treatment, fruits ripened, and ethylene was detected in all treatments and cultivars. We confirmed that ‘Kaimitsu’ exhibited fruit development without artificial pollination or CPPU treatment in another season. Furthermore, in ‘Kaimitsu’, parthenocarpic fruits without CPPU treatment were smaller than artificial pollinated fruits, and natural fruit drop was extensive. Thus, parthenocarpy of ‘Kaimitsu’ was thought to be unstable. These results showed that excessive parthenocarpy may be successful in kiwifruit depending on specific cultivars.

An integrative transcriptomic and genomic analysis reveals novel insights into the hub genes and regulatory networks associated with rubber synthesis in H. brasiliensis

Rubber tree (Hevea brasiliensis) is an important tropical plant that produces natural rubber; however, the hub genes and regulatory networks associated with rubber synthesis remain largely unclear. In this work, 129 publically available RNA-seq datasets were collected to perform gene co-expression network analysis in rubber tree. In total, 25 co-expressed gene modules (M1-M25) were identified, and the molecular functions and hub genes of each module were systematically analyzed. Associations between modules and tissues/stresses revealed that modules were significantly associated with stresses in the tissues where the modules were specifically highly expressed. Notably, module M7 was highly expressed in latex and dramatically responsive to ethylene, jasmonate, and tapping panel dryness treatments. Besides, the genes from M7 were significantly enriched in isoprenoid metabolism, indicating a great contribution of this module to rubber biosynthesis. The co-expression network of rubber biosynthesis genes from M7 revealed that small rubber particle protein 1 (SRPP1), cis-prenyltransferase 2 (CPT2), and rubber elongation factor 1 (REF1) were the most connected hub genes participating in rubber biosynthesis. Two candidate cis-regulatory motifs and three transcription factors that might regulate rubber biosynthesis were further identified. Genomic evolutionary analysis suggested that the expansion of two independently evolved REF/SRPP clusters, II (containing SRPP1) and V (containing REF1), was critical for rubber synthesis. Together, this integrative transcriptomic and genomic analysis provides novel insights into the hub genes and regulatory networks underlying rubber synthesis in H. brasiliensis.

The N1-Methyladenosine Methylome of Petunia mRNA.

N1-methyladenosine is a unique type of base methylation in that it blocks Watson-Crick base pairing and introduces a positive charge. m1A is prevalent in yeast and mammalian mRNA and plays a functional role. However, little is known about the abundance, dynamics, and topology of this modification in plant mRNA. Dot blotting and liquid chromatography tandem mass spectrometry analyses revealed a dynamic pattern of m1A mRNA modification in various tissues and at different developmental stages in petunia (Petunia hybrida), a model system for plant growth and development. We performed transcriptome-wide profiling of m1A in petunia mRNA by m1A mRNA immunoprecipitation followed by a deep-sequencing approach (m1A-seq, using an m1A-specific antibody). m1A-seq analysis identified 4,993 m1A peaks in 3,231 genes expressed in petunia corollas; there were 251 m1A peaks in which A residues were partly replaced by thymine and/or reverse transcription stopped at an adenine site. m1A was enriched in coding sequences, with single peaks located immediately after start codons. Ethylene treatment upregulated 400 m1A peaks in 375 mRNAs and downregulated 603 m1A peaks in 530 mRNAs in petunia corollas; 975 m1A peaks in mRNA were only detected in corollas treated with air and 430 were only detected in corollas treated with ethylene. Silencing of petunia tRNA-specific methyltransferase 61A (PhTRMT61A) reduced the m1A level in mRNA in vivo and in vitro. In addition, PhTRMT61A silencing caused abnormal leaf development, and the PhTRMT61A protein was localized to the nucleus. Thus, m1A in mRNA is an important epitranscriptome marker and plays a role in plant growth and development.

Expression of the tomato WRKY gene, SlWRKY23, alters root sensitivity to ethylene, auxin and JA and affects aerial architecture in transgenic Arabidopsis.

WRKY transcription factors (TFs) are a large plant-specific family of TFs that govern development and biotic/abiotic stress responses in plants. We have identified SlWRKY23 as a gene primarily expressed in roots. SlWRKY23 encodes a protein of 320 amino acids that functions as a transcriptional activator. It is transcriptionally up-regulated by ethylene, BAP and salicylic acid treatment but suppressed by IAA. Expression of SlWRKY23 in transgenic Arabidopsis affects sensitivity of roots to ethylene, JA and auxin with transgenic plants showing hypersensitivity to ethylene, JA and auxin-mediated primary root growth inhibition. This hypersensitivity is correlated with higher expression of ERF1 and ARF5 that mediate responses to these hormones. SlWRKY23 expression also affects aerial growth with transgenic plants showing greater number of leaves but smaller rosettes. Flowering time is reduced in transgenic lines and these plants also show a greater number of inflorescence branches, siliques and seeds. The siliques are longer and compactly packed with seeds but seeds are smaller in size. Root biomass shows a 25% decrease in transgenic SlWRKY23 Arabidopsis plants at harvest compared with controls. The studies show that SlWRKY23 regulates plant growth possibly through modulation of genes controlling hormone responses.

Effects of ethylene and 1-methylcyclopropene treatments on physiological changes and ripening-related gene expression of ‘Mopan’ persimmon fruit during storage

Abstract ‘Mopan’ persimmon (Diospyros kaki L. cv. Mopan) is an economically important persimmon cultivar that is widely grown in northern China areas. Expanded understanding of postharvest fruit physiological changes and the role that ethylene plays will enhance the efficiency of fruit storage and marketing. Treatments with ethylene and 1-MCP on ‘Mopan’ persimmons showed opposite effects on softening, color, total soluble solid (TSS), total and soluble tannin contents, ethylene production and respiration rate during fruit storage. Ethylene and 1-MCP treatments also affected the expression of five ethylene signaling genes DkCTR1, DkETR1, DkETR2, DkERF22 and DkERF19, three de-astringent related genes DkADH1, DkPDC1 and DkPDC2, and four cell wall-hydrolyzing enzyme genes DkPG1, DkXTH2, DkPME1 and Dkβ-GAL1 during fruit storage. High correlations were observed between ethylene signal pathway genes, physiological characters and ripening related gene expression. The results indicate that ethylene greatly accelerate fruit ripening, and the ripening process can be inhibited by 1-MCP treatment both on physiological and molecular levels. The application of 1-MCP delayed seven to ten days on fruit ripening compared to controls. The overall information obtained from this study demonstrates that ethylene plays the critical roles in postharvest ripening, gene expressions and physiological property changes of ‘Mopan’ persimmon fruit during storage. The suppression of ethylene activity by 1-MCP provides the industry with an applicable technology to improve postharvest processing and ‘Mopan’ persimmon fruit value.

Low temperature modulates natural peel degreening in lemon fruit independently of endogenous ethylene.

Peel degreening is an important aspect of fruit ripening in many citrus fruit, and previous studies have shown that it can be advanced by ethylene treatment or by low-temperature storage. However, the important regulators and pathways involved in natural peel degreening remain largely unknown. To determine how natural peel degreening is regulated in lemon fruit (Citrus limon), we studied transcriptome and physiochemical changes in the flavedo in response to ethylene treatment and low temperatures. Treatment with ethylene induced rapid peel degreening, which was strongly inhibited by the ethylene antagonist, 1-methylcyclopropene (1-MCP). Compared with 25 ºC, moderately low storage temperatures of 5-20 °C also triggered peel degreening. Surprisingly, repeated 1-MCP treatments failed to inhibit the peel degreening induced by low temperature. Transcriptome analysis revealed that low temperature and ethylene independently regulated genes associated with chlorophyll degradation, carotenoid metabolism, photosystem proteins, phytohormone biosynthesis and signalling, and transcription factors. Peel degreening of fruit on trees occurred in association with drops in ambient temperature, and it coincided with the differential expression of low temperature-regulated genes. In contrast, genes that were uniquely regulated by ethylene showed no significant expression changes during on-tree peel degreening. Based on these findings, we hypothesize that low temperature plays a prominent role in regulating natural peel degreening independently of ethylene in citrus fruit.

An ERF Transcription Factor Gene from Malus baccata (L.) Borkh, MbERF11, Affects Cold and Salt Stress Tolerance in Arabidopsis

Apple, as one of the most important economic forest tree species, is widely grown in the world. Abiotic stress, such as low temperature and high salt, affect apple growth and development. Ethylene response factors (ERFs) are widely involved in the responses of plants to biotic and abiotic stresses. In this study, a new ethylene response factor gene was isolated from Malus baccata (L.) Borkh and designated as MbERF11. The MbERF11 gene encoded a protein of 160 amino acid residues with a theoretical isoelectric point of 9.27 and a predicated molecular mass of 17.97 kDa. Subcellular localization showed that MbERF11 was localized to the nucleus. The expression of MbERF11 was enriched in root and stem, and was highly affected by cold, salt, and ethylene treatments in M. baccata seedlings. When MbERF11 was introduced into Arabidopsis thaliana, it greatly increased the cold and salt tolerance in transgenic plant. Increased expression of MbERF11 in transgenic A. thaliana also resulted in higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), higher contents of proline and chlorophyll, while malondialdehyde (MDA) content was lower, especially in response to cold and salt stress. Therefore, these results suggest that MbERF11 probably plays an important role in the response to cold and salt stress in Arabidopsis by enhancing the scavenging capability for reactive oxygen species (ROS).

Effects of 1-Methylcyclopropene (1-MCP) and Ethylene on Postharvest Lignification of Common Beans (Phaseolus vulgaris L).

Postharvest 1-methylcyclopropene (1-MCP) treatment can inhibit the lignification of fruits and vegetables. The mode of action of 1-MCP is through inhibiting ethylene production, but the effect of 1-MCP and ethylene on lignification of common beans remains unknown. This work compared the effect of 0.5 μL L–1 1-MCP and 100 μL L–1 ethylene on the lignification of common beans during storage. Postharvest 1-MCP significantly inhibited the increase of the lignified cell group, sclerenchyma became thicker, vascular bundles thickened, and lignified cells grew during storage, while ethylene was the opposite. 1-MCP inhibited the increase in the respiration rate, sucrose phosphate synthase (SPS), sucrose synthase (SuSy), phenylalanine ammonialyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD), whereas ethylene increased all of them. Ethylene treatment stimulated and 1-MCP inhibited the decline of reducing sugar and cellulose content. Expression of genes, including PvACO1, PvAOG1, PvSuSy2, PvPAL3, Pv4CL1, and PvCOMT1, with the lignin content being significantly increased in common beans during storage. 1-MCP treatment markedly inhibited the expression of PvACO1, PvSuSy2, PvPAL3, Pv4CL1, and PvCOMT1 genes, while strengthened the expression of PvETR1 and PvAOG1, while ethylene was the opposite. This work provides evidence that ethylene or abscisic acid (ABA) may play an important role in 1-MCP regulation of postharvest lignification in common beans and provides strategies for preserving the quality of fruits and vegetables during storage.

Transcriptome Analysis of ‘Haegeum’ Gold Kiwifruit Following Ethylene Treatment to Improve Postharvest Ripening Quality

Fruit ripening involves changes in physical, physiological and metabolic activities through the actions of enzymes and regulatory genes. This study was initiated to identify the genes related to the ripening of kiwifruit. Gold ‘Haegeum’ kiwifruit is a yellow-fleshed kiwifruit cultivar usually used for fresh marketing. The fruit is harvested at a physiologically mature but unripe stage for proper storage, marketing distribution and longer shelf life. To identify the differentially expressed genes (DEGs) during ripening, fruit treated with ethylene were compared with control fruit that ripened naturally without ethylene treatment. Firmness, respiration rate, ethylene production rate, total soluble solids (TSS), titratable acidity (TA), brix acid ratio (BAR) and overall acceptability were taken during the study as fruit ripening indicators. Total mRNAs were sequenced by Illumina high-throughput sequencing platform and the transcriptome gene set was constructed by de novo assembly. We identified 99,601 unigenes with an average length of 511.77 bp in transcriptome contigs. A total of 28,582 differentially expressed unigenes were identified in the ethylene treatment vs. control. Of these 28,582 unigenes, 13,361 and 15,221 genes were up- and downregulated, respectively, in the treated fruit. The results also showed that 1682 and 855 genes were up- and downregulated, respectively, more than 2-fold at p < 0.05 in fruit treated with ethylene as compared with the control fruit. Moreover, we identified 75 genes showing significantly different expression; 42 were upregulated, and 33 were downregulated. A possible category of the identified ripening-related genes was also made. The findings of this study will add to the available information on the effect of ethylene treatment on ripening and the related changes of kiwifruit at the genomic level, and it could assist the further study of genes related to ripening for kiwifruit breeding and improvement.

GmNAC8 acts as a positive regulator in soybean drought stress

NAC proteins represent one of the largest transcription factor (TF) families involved in the regulation of plant development and the response to abiotic stress. In the present study, we elucidated the detailed role of GmNAC8 in the regulation of drought stress tolerance in soybean. The GmNAC8 protein was localized in the nucleus, and expression of the GmNAC8 gene was significantly induced in response to drought, abscisic acid (ABA), ethylene (ETH) and salicylic acid (SA) treatments. Thus, we generated GmNAC8 overexpression (OE1 and OE2) and GmNAC8 knockout (KO1 and KO2) lines to determine the role of GmNAC8 in drought stress tolerance. Our results revealed that, compared with the wild type (WT) plant, GmNAC8 overexpression and GmNAC8 knockout lines exhibited significantly higher and lower drought tolerance, respectively. Furthermore, the SOD activity and proline content were significantly higher in the GmNAC8 overexpression lines and significantly lower in the GmNAC8 knockout lines than in the WT plants under drought stress. In addition, GmNAC8 protein was found to physically interact with the drought-induced protein GmDi19-3 in the nucleus. Moreover, the GmDi19-3 expression pattern showed the same trend as the GmNAC8 gene did under drought and hormone (ABA, ETH and SA) treatments, and GmDi19-3 overexpression lines (GmDi19-3-OE9, GmDi19-3-OE10 and GmDi19-3-OE31) showed enhanced drought tolerance compared to that of the WT plants. Hence, the above results indicated that GmNAC8 acts as a positive regulator of drought tolerance in soybean and inferred that GmNAC8 probably functions by interacting with another positive regulatory protein, GmDi19-3.