Regulation Of Ethylene Production Research Articles

Autophagy-regulated ethylene synthesis mediates fruit ripening by affecting the accumulation of lycopene, sugars and organic acids in tomato

Autophagy is a universal cellular process in eukaryotes that plays a critical role in plant growth and stress response. However, the role of autophagy in fruit ripening is largely unknown. Here, we demonstrated that most autophagy-related genes (ATGs) were up-regulated during tomato (Solanum lycopersicum L.) fruit ripening. By using mutants of different autophagy pathway genes (ATG6, ATG10, ATG18a), we revealed that the deficiency of autophagy delayed the ripening of fruit. Compared with wild-type (WT), the production of ethylene was significantly reduced and the accumulation of lycopene was delayed in atg mutants during fruit ripening. We also observed the contents of glucose and fructose were both significantly decreased in atg mutants compared with WT, while the content of organic acids showed the opposite trend. Additionally, the negative regulator of ethylene production, APETALA2a (AP2a), interacted with ATG8 through a specific ATG8-interacting motif (AIM) and could be degraded through the autophagy pathway. These results demonstrate that autophagy plays a critical role in fruit ripening by regulating ethylene production and the accumulation of pigments, sugars and organic acids in tomato.

Preharvest Nano-calcium Reduces the Table Grape Berry Abscission by Regulating Ethylene Production During Storage

Preharvest Nano-calcium Reduces the Table Grape Berry Abscission by Regulating Ethylene Production During Storage

The miR156/SPL12 module orchestrates fruit colour change through directly regulating ethylene production pathway in blueberry.

Colour change is an important event during fruit ripening in blueberry. It is well known that miR156/SPLs act as regulatory modules mediating anthocyanin biosynthesis and ethylene plays critical roles during colour change, but the intrinsic connections between the two pathways remain poorly understood. Previously, we demonstrated that blueberry VcMIR156a/VcSPL12 affects the accumulation of anthocyanins and chlorophylls in tomato and Arabidopsis. In this study, we first showed that VcMIR156a overexpression in blueberry led to enhanced anthocyanin biosynthesis, decreased chlorophyll accumulation, and, intriguingly, concomitant elevation in the expression of ethylene biosynthesis genes and the level of the ethylene precursor ACC. Conversely, VcSPL12 enhanced chlorophyll accumulation and suppressed anthocyanin biosynthesis and ACC synthesis in fruits. Moreover, the treatment with ethylene substitutes and inhibitors attenuated the effects of VcMIR156a and VcSPL12 on pigment accumulation. Protein-DNA interaction assays indicated that VcSPL12 could specifically bind to the promoters and inhibit the activities of the ethylene biosynthetic genes VcACS1 and VcACO6. Collectively, our results show that VcMIR156a/VcSPL12 alters ethylene production through targeting VcACS1 and VcACO6, therefore governing fruit colour change. Additionally, VcSPL12 may directly interact with the promoter region of the chlorophyll biosynthetic gene VcDVR, thereby activating its expression. These findings established an intrinsic connection between the miR156/SPL regulatory module and ethylene pathway.

Genome-Wide Analysis of the Amino Acid Permeases Gene Family in Wheat and TaAAP1 Enhanced Salt Tolerance by Accumulating Ethylene.

Amino acid permeases (AAPs) are proteins of the integral membrane that play important roles in plant growth, development, and responses to various stresses. The molecular functions of several AAPs were characterized in Arabidopsis and rice, but there is still limited information on wheat. Here, we identified 51 AAP genes (TaAAPs) in the wheat genome, classified into six groups based on phylogenetic and protein structures. The chromosome location and gene duplication analysis showed that gene duplication events played a crucial role in the expansion of the TaAAPs gene family. Collinearity relationship analysis revealed several orthologous AAPs between wheat and other species. Moreover, cis-element analysis of promoter regions and transcriptome data suggested that the TaAAPs can respond to salt stress. A TaAAP1 gene was selected and transformed in wheat. Overexpressing TaAAP1 enhanced salt tolerance by increasing the expression of ethylene synthesis genes (TaACS6/TaACS7/TaACS8) and accumulating more ethylene. The present study provides an overview of the AAP family in the wheat genome as well as information on systematics, phylogenetics, and gene duplication, and shows that overexpressing TaAAP1 enhances salt tolerance by regulating ethylene production. These results serve as a theoretical foundation for further functional studies on TaAAPs in the future.

Ethylene and spermine attenuate chromium-inhibited photosynthetic functions by improving nitrogen and sulfur assimilation and antioxidant system in mustard

Phytohormones signaling is known for the regulation of metabolites synthesis, photosynthetic performance and abiotic stress acclimation in plants. We investigated the influence of ethylene (sourced as ethephon; 2-chloroethyl phosohonic acid, ETH) and spermine (Spm; polyamine) in alleviating the chromium (Cr)-triggered oxidative stress in the mustard (Brassica juncea cv. Varuna). The individual additions of 200 µL L−1 ETH and 1 mM Spm improved photosynthetic and growth parameters in the absence of Cr, but the Cr presence increased oxidative stress and the formation of stress (excess) ethylene, inhibiting photosynthesis, and growth. The application of ETH and Spm together in the absence of Cr, improved photosynthesis conspicuously. In the presence of Cr, ETH and Spm application improved photosynthesis by upregulation of psbA and psbB genes expression, and reducing oxidative stress, stress ethylene formation, and increase in activity of antioxidant enzymes, upregulation of ascorbate peroxidase (APX) and glutathione reductase (GR) genes, and nitrogen (N) and sulfur (S) assimilation. The possible ways in which ethylene and Spm interact in the mitigation of Cr-triggered oxidative damage are discussed. The study will provide insight into the mechanisms of N and S assimilation, antioxidant system, and regulation of ethylene production under the influence of ETH and Spm, and the strategy may be adopted for the sustainability of mustard plants under Cr stress.

WRKY29 transcription factor regulates ethylene biosynthesis and response in arabidopsis

The gaseous phytohormone ethylene participates in a lot of physiological processes in plants. 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS, EC 4.4.1.14) and the ACC oxidase (ACO, EC 1.14.17.4) are key enzymes in ethylene biosynthesis. However, how ACSs and ACOs are regulated at the transcriptional level is largely unknown. In the present study, we showed that an Arabidopsis (Arabidopsis thaliana) WRKY-type transcription factor (TF), WRKY29 positively regulated the expression of ACS5, ACS6, ACS8, ACS11 and ACO5 genes and thus promoted basal ethylene production. WRKY29 protein was localized in nuclei and was a transcriptional activator. Overexpression of WRKY29 caused pleiotropic effect on plant growth, development and showed obvious response even without ACC treatment. Inducible overexpression of WRKY29 also reduced primary root elongation and lateral root growth. A triple response assay of overexpression and mutant seedlings of WRKY29 showed that overexpression seedlings had shorter hypocotyls than the transgenic GFP (Green Fluorescence Protein) control, while mutants had no difference from wild-type. A qRT-PCR assay demonstrated that expression of multiple ACSs and ACO5 was up-regulated in WRKY29 overexpression plants. A transactivation assay through dual luciferase reporter system confirmed the regulation of promoters of ACS5, ACS6, ACS8, ACS11 and ACO5 by WRKY29. Both in vivo chromatin immunoprecipitation (ChIP)- quantitative PCR and in vitro electrophoretic mobility shift assay (EMSA) revealed that WRKY29 directly bound to the promoter regions of its target genes. Taken together, these results suggest that WRKY29 is a novel TF positively regulating ethylene production by modulating the expression of ACS and ACO genes.

The HY5 transcription factor negatively regulates ethylene production by inhibiting ACS1 expression under blue light conditions in pear

Ethylene is the main factor controlling fruit ripening of pear (Pyrus ussuriensis). Ethylene production rate is negatively correlated with fruit shelf life; therefore, it is important to decrease the ethylene levels for optimal fruit storage. Here, we observed that blue light treatment could inhibit ethylene production and promote the expression of ELONGATED HYPOCOTYL 5 (PuHY5), a basic leucine zipper domain (bZIP) transcription factor. The following studies showed that PuHY5 could bind to the promoter of ACC synthase 1 (PuACS1), a rate-limiting enzyme in ethylene biosynthesis, and inhibit its expression. For pears in which PuHY5 was silenced, the ethylene production and PuACS1 expression were much higher than those in the control fruit. These results demonstrated that blue light inhibited ethylene production through the induction of PuHY5 in pear. Our finding provides a new method for prolonging fruit shelf life.

Sucrose + 8-HQC improves the postharvest quality of lily and rose cut flowers by regulating ROS-scavenging systems and ethylene release

The objective of the present investigation was to study the effects of sucrose + 8-hydroxyquinoline citrate (8-HQC) on the reactive oxygen species (ROS)-scavenging systems and ethylene release during the vase life of cut lilies (ethylene-insensitive type) and roses (ethylene-sensitive type). ROS production and the degree of lipid peroxidation increased with the senescence of cut lily and rose flowers. The treatment with sucrose + 8-HQC enhanced ROS-scavenging abilities, decreased Superoxide radical (O2.−) release and mitigated the oxidative damage marked by lower malondialdehyde (MDA) level, although the up-regulated extent of each antioxidant enzyme was not exactly the same in both cut flower species. The treatment of sucrose + 8-HQC decreased the level of proline in cut rose, which suggested water stress of cut rose was alleviated. On the other hand, the increase of proline in cut lily due to sucrose + 8-HQC was elaborated. The preservation effect induced by sucrose + 8-HQC was involved in the regulation of ethylene production in ethylene-sensitive cut flowers, not in ethylene-insensitive cut flowers. From the results of ethylene and proline analysis, it can be found that there are differences in the regulation mechanism of sucrose on the fresh-keeping of the two cut flowers, but the treatment with sucrose and 8-HQC can improve the postharvest quality of cut flowers with different sensitivity to ethylene by enhancing ROS-scavenging activities and alleviating lipid peroxidation.

Possible mechanisms for the equilibrium of ACC and role of ACC deaminase-producing bacteria.

Plant growth-promoting rhizobacteria (PGPR) actively colonize the plant rhizosphere, which not only stimulates plants' growth and development but also mitigates the adverse effects of abiotic stressors. Besides other techniques and approaches used for the alleviation of abiotic stress conditions, the utilization of PGPR with multiplant growth-promoting traits is desirable because the application of PGPR is pragmatic, sustainable, and environmentally friendly. In the past four decades, numerous ACC deaminase-producing PGPR have been reported for the improvement of crop plants' growth and development under different abiotic stress conditions. Since 1-aminocyclopropane-1-carboxylate (ACC) deaminase producing PGPR regulates ethylene production by utilizing the exuded ACC, which is an immediate precursor of ethylene biosynthesis. However, little is known about the basic mechanism involved in the acquisition of ACC by ACC deaminase-producing bacteria since the enzyme ACC deaminase is localized inside the bacterial cells and ACC is exuded into the rhizosphere from plant roots. In the present article, we proposed candidate attractants involved in the transfer of ACC into ACC deaminase-producing bacteria. Additionally, we discussed the importance and relation of these candidate attractants with ACC deaminase under abiotic stress conditions. KEY POINTS: • The ethylene precursor, ACC, exude from plant tissues under abiotic stresses • ACC deaminase activity of PGPR localized in the cytoplasm and periplasm of bacteria • Proposed candidate attractants for the transfer and equilibrium of exuded ACC.

1H-Cyclopropabenzene and 1H-Cyclopropa[b]naphthalene Fumigation Suppresses Climacteric Ethylene and Respiration Rates and Modulates Fruit Quality in Long-term Controlled Atmosphere-Stored ‘Gold Rush’ Pear Fruit

‘Gold Rush’ pear (Pyrus communis L.) is a russet-coloured fruit with soft buttery textured flesh and is gaining wide popularity in Australia and other countries along with other pear cultivars. The fruit are sensitive to ethylene, and exposure even at very low concentrations significantly reduces the storage duration as well as fruit quality during storage. The efficacy of two new ethylene antagonist compounds, namely, 1H-cyclopropabenzene (BC) and 1H-cyclopropa[b]naphthalene (NC), as well as 1-methylcyclopropene (1-MCP) in regulating ethylene production, respiration rates and maintaining the fruit quality of ‘Gold Rush' pear during 150 d and 200 d of controlled atmosphere (CA) storage (2.3 ± 0.5% O2 and 0.4 ± 0.15% CO2 and 0.50 ± 0.71 °C) was investigated. The pear fruit was fumigated with 1 µM BC (0.09 µL L−1) or 1 µM NC (0.14 µL L−1) or 18 µM 1-MCP (1 µL L−1) for 18 h at room temperature and the untreated fruit was considered as the control. Following 150 d and 200 d CA storage, the fruit fumigated with BC and NC exhibited significantly reduced ethylene and respiratory climacteric peak rates and they were lowest in the fruit treated with 1-MCP. The pear fruit fumigated with ethylene antagonists (BC, NC and 1-MCP) exhibited lower physiological loss of weight (PLW) (up to 2.06 times) and higher fruit firmness (up to 1.07 times) throughout the CA storage period, compared to the control fruit. The fruit fumigated with BC and NC had lower levels of SSC, glucose and sorbitol compared to other treatments. There was no significant effect of ethylene antagonist treatments on levels of individual organic acids, total phenols, ascorbic acid and total antioxidant capacity of the fruit pulp. Therefore, new ethylene antagonist compounds, BC and NC, exhibit the potential to act as ethylene antagonists in long-term CA-stored ‘Gold Rush’ pears to retard the fruit ripening process, extend storage life and maintain the fruit quality. The effectiveness of the different concentrations of BC and NC in suppressing ethylene production in different cultivars of pears warrants further investigation.

Influences of sea water on the ethylene-biosynthesis, senescence-associated gene expressions, and antioxidant characteristics of Arabidopsis plants

We evaluated the physiological and antioxidant characteristics of Arabidopsis thaliana (At) plants grown in different sea water (SW) products containing trace elements, namely RO3, 300K, and 340K, at various dilutions. The synthetic water (namely 300K-Test), a mixture of the main ions of SW including 143.08 mg L-1 Mg2+, 5.74 mg L-1 Na+, 170 mg L-1 K+, and 33.5 mg L-1 Ca2+ with equal concentrations to those in 300K SW without trace elements, was also used to culture At plants and study the influences that the major ions had on regulating ethylene production. The ethylene-biosynthesis (ACS7 and ACO2) and senescence-associated (NAP, SAG113, and WRKY6) gene expressions in SW- and ionic-treated At plants in response to transcriptional signaling pathways of ethylene response mechanisms were also investigated. Our results show that down-regulation of the ACS7 gene in 300K-treated plants significantly reduced the ethylene content but remarkably increased chlorophyll, total phenol, and DPPH radical scavenging accumulations and strengthened the salt tolerance of 300K-treated plants. The expression of the ACS7 gene of At plants under 300K, Ca2+, Mg2+, and Na+ treatments was correlated with decreases in NAP, SAG113, and WRKY6 gene expressions. The application of Ca2+ increased total phenol content and reduced the accumulation of superoxide, which in combination decreases plant aging brought on by ethylene. However, K+ treatment inhibited SGA113 gene expression, resulting in reducing ACS7 gene expression and ethylene content. The characterization and functional analysis of these genes should facilitate our understanding of ethylene response mechanisms in plants.

Genetic Interaction Among Phytochrome, Ethylene and Abscisic Acid Signaling During Dark-Induced Senescence in Arabidopsis thaliana.

Leaf senescence is induced by various internal and external stimuli. Dark-induced senescence has been extensively investigated, but the detailed mechanism underlying it is not well understood. The red light/far-red light receptor phytochrome B and its downstream transcription factors, PYHTOCHROME INTERACTING FACTORs (PIFs) 4 and 5, are known to play an important role in dark-induced senescence. Furthermore, the senescence-inducing phytohormones, ethylene and abscisic acid (ABA) are reported to be involved in dark-induced senescence. In this study, we analyzed the relationship between ethylene, ABA and PIFs in dark-induced leaf senescence. A triple mutant of the core ABA signaling components; SNF1-related protein kinases 2D (SRK2D), SRK2E, and SRK2I, displayed an ABA insensitive phenotype in ABA-induced senescence, whilst the ethylene insensitive mutant ein2 demonstrated low sensitivity to ABA, suggesting that ethylene signaling is involved in ABA-induced senescence. However, the pif4 pif5 mutant did not display low sensitivity to ABA, suggesting that PIF4 and PIF5 act upstream of ABA signaling. Although PIF4 and PIF5 reportedly regulate ethylene production, the triple mutant ein2 pif4 pif5 showed a stronger delayed senescence phenotype than ein2 or pif4 pif5, suggesting that EIN2 and PIF4/PIF5 partially regulate leaf senescence independently of each other. While direct target genes for PIF4 and PIF5, such as LONG HYPOCOTYL IN FAR-RED1 (HFR1) and PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1), showed transient upregulation under dark conditions (as is seen in the shade avoidance response), expression of STAY GREEN1 (SGR1), ORESARA1 (ORE1) and other direct target genes of PIF5, continued to increase during dark incubation. It is possible that transcription factors other than PIF4 and PIF5 are involved in the upregulation of SGR1 and ORE1 at a later stage of dark-induced senescence. Possible candidates are senescence-induced senescence regulators (SIRs), which include the NAC transcription factors ORE1 and AtNAP. In fact, ORE1 is known to bind to the SGR1 promoter and promotes its expression. It is therefore inferred that the phytochrome-PIF pathway regulates initial activation of senescence and subsequently, induced SIRs reinforce leaf senescence during dark-induced senescence.

Enhancement of growth and salt tolerance of rice seedlings (Oryza sativa L.) by regulating ethylene production with a novel halotolerant PGPR strain Glutamicibacter sp. YD01 containing ACC deaminase activity

Plant growth-promoting rhizobacteria can stimulate not only plant growth and development, but also alleviate the negative effects on plants caused by abiotic stresses. In this study, a novel halotolerant strain was isolated and identified as Glutamicibacter sp. (YD01) using 16S rDNA analysis. This strain tolerated up to 10% NaCl and showed two growth-promoting traits such as 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme activity and IAA production. Glutamicibacter sp. YD01 inoculation could enhance tolerance of rice (Oryza sativa L.) plants to salt stress by regulation of plant ethylene production, ACC content, ACC oxidase activity and improving K+ acquisition. Moreover, strain YD01-inoculated rice exhibited lower levels of Na+ accumulation and electrolyte leakage under salt treatment compared to non-inoculated ones. Inoculated rice also showed higher transcript levels of genes encoding antioxidants and genes involved in salt tolerance than the plants with no inoculation. In summary, this study showed the important role of Glutamicibacter sp. YD01 in the alleviation of the adverse effects of salt stress on growth and development of rice plants through mediation of phytohormone (ethylene) and ROS accumulation, maintaining ion homeostasis, improving photosynthetic capacity and enhancing stress-responsive genes expression. This work provides an economic approach of promoting growth and development of plants under salt stress treatment.

Phytohormones (Auxin, Gibberellin) and ACC Deaminase In Vitro Synthesized by the Mycoparasitic Trichoderma DEMTkZ3A0 Strain and Changes in the Level of Auxin and Plant Resistance Markers in Wheat Seedlings Inoculated with this Strain Conidia.

Both hormonal balance and plant growth may be shaped by microorganisms synthesizing phytohormones, regulating its synthesis in the plant and inducing plant resistance by releasing elicitors from cell walls (CW) by degrading enzymes (CWDE). It was shown that the Trichoderma DEMTkZ3A0 strain, isolated from a healthy rye rhizosphere, colonized the rhizoplane of wheat seedlings and root border cells (RBC) and caused approximately 40% increase of stem weight. The strain inhibited (in over 90%) the growth of polyphagous Fusarium spp. (F. culmorum, F. oxysporum, F. graminearum) phytopathogens through a mechanism of mycoparasitism. Chitinolytic and glucanolytic activity, strongly stimulated by CW of F. culmorum in the DEMTkZ3A0 liquid culture, is most likely responsible for the lysis of hyphae and macroconidia of phytopathogenic Fusarium spp. as well as the release of plant resistance elicitors. In DEMTkZ3A0 inoculated plants, an increase in the activity of the six tested plant resistance markers and a decrease in the concentration of indoleacetic acid (IAA) auxin were noted. IAA and gibberellic acid (GA) but also the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) enzyme regulating ethylene production by plant were synthesized by DEMTkZ3A0 in the liquid culture. IAA synthesis was dependent on tryptophan and negatively correlated with temperature, whereas GA synthesis was positively correlated with the biomass and temperature.

1-Methylcyclopropene as an Effective Ethylene Inhibitor to Extend Musa acuminata Colla ‘Muli’ Postharvest Quality

Musa acuminata Colla ‘Muli’ is one of the most popular banana variety in Indonesia. As a commodity that is consumed fresh, is important to regulate the ethylene production of climacteric fruit in order to extend the shelf life and reduce deterioration. 1-MCP (1-Methylcycloprophene) is a potential chemical that can effectively regulate ethylene production in Muli bananas. In this study, 1-MCP in different concentrations (0, 0.25, 0.50 and 1.00 µL L-1) were applied at two maturation stages to observe the effects. Lower 1-MCP concentration was effective in delaying fruit ripening on mature green stage shown by fruit firmness maintenance and improved shelf life up to 4.5 days longer than control. The application of 1-MCP was effective in delaying fruit ripening if applied prior to climacteric stage.

High-density genetic map construction and quantitative trait loci analysis of the stony hard phenotype in peach based on restriction-site associated DNA sequencing

BackgroundPeach (Prunus persica) is an important fruit crop that generally softens rapidly after harvest resulting in a short shelf-life. By contrast, stony hard (SH) peach fruit does not soften and hardly produces ethylene. To explore the candidate genes responsible for the SH phenotype, a high-density genetic map was constructed by restriction-site associated DNA sequencing technology.ResultsIn the present study, the linkage map consisted of 1310 single nucleotide polymorphism markers, spanning 454.2 cM, with an average marker distance of 0.347 cM. The single nucleotide polymorphisms were able to anchor eight linkage groups to their corresponding chromosomes. Based on this high-density integrated peach linkage map and two years of fruit phenotyping, two potential quantitative trait loci for the SH trait were identified and positioned on the genetic map. Additionally, Prupe.6G150900.1, a key gene in abscisic acid (ABA) biosynthesis, displayed a differential expression profile identical to the ABA accumulation pattern: mRNA transcripts were maintained at a high level during storage of SH peaches but occurred at low levels in melting fruit.ConclusionThus Prupe.6G150900.1 might play a crucial role in the SH phenotype of peach in which ABA negatively regulates ethylene production. Also, this high-density linkage map of peach will contribute to the mapping of important fruit traits and quantitative trait loci identification.

An apple NAC transcription factor enhances salt stress tolerance by modulating the ethylene response.

It is known that ethylene signaling is involved in the regulation of the salt stress response. However, the molecular mechanism of ethylene-regulated salt stress tolerance remains largely unclear. In this study, an apple NAM ATAF CUC transcription factor, MdNAC047, was isolated and functionally characterized to be involved in ethylene-modulated salt tolerance. MdNAC047 gene was significantly induced by salt treatment and its overexpression conferred increased tolerance to salt stress and facilitated the release of ethylene. Quantitative real-time-PCR analysis demonstrated that overexpression of MdNAC047 increased the expression of ethylene-responsive genes. Electrophoretic mobility shift assay, yeast one-hybrid and dual-luciferase assays suggested that MdNAC047 directly binds to the MdERF3 (ETHYLENE RESPONSE FACTOR) promoter and activates its transcription. In addition, genetic analysis assays indicated that MdNAC047 regulates ethylene production at least partially in an MdERF3-dependent pathway. Overall, we found a novel 'MdNAC047-MdERF3-ethylene-salt tolerance' regulatory pathway, which provide new insight into the link between ethylene and salt stress.

The FBH family of bHLH transcription factors controls ACC synthase expression in sugarcane.

Ethylene is a phytohormone involved in the regulation of several aspects of plant development and in responses to biotic and abiotic stress. The effects of exogenous application of ethylene to sugarcane plants are well characterized as growth inhibition of immature internodes and stimulation of sucrose accumulation. However, the molecular network underlying the control of ethylene biosynthesis in sugarcane remains largely unknown. The chemical reaction catalyzed by 1-aminocyclopropane-1-carboxylic acid synthase (ACS) is an important rate-limiting step that regulates ethylene production in plants. In this work, using a yeast one-hybrid approach, we identified three basic helix-loop-helix (bHLH) transcription factors, homologs of Arabidopsis FBH (FLOWERING BHLH), that bind to the promoter of ScACS2 (Sugarcane ACS2), a sugarcane type 3 ACS isozyme gene. Protein-protein interaction assays showed that sugarcane FBH1 (ScFBH1), ScFBH2, and ScFBH3 form homo- and heterodimers in the nucleus. Gene expression analysis revealed that ScFBHs and ScACS2 transcripts are more abundant in maturing internodes during afternoon and night. In addition, Arabidopsis functional analysis demonstrated that FBH controls ethylene production by regulating transcript levels of ACS7, a homolog of ScACS2. These results indicate that ScFBHs transcriptionally regulate ethylene biosynthesis in maturing internodes of sugarcane.

Editorial: Ethylene's Role in Plant Mineral Nutrition.

Editorial: Ethylene's Role in Plant Mineral Nutrition.

Abscisic Acid Antagonizes Ethylene Production through the ABI4-Mediated Transcriptional Repression of ACS4 and ACS8 in Arabidopsis

Increasing evidence has revealed that abscisic acid (ABA) negatively modulates ethylene biosynthesis, although the underlying mechanism remains unclear. To identify the factors involved, we conducted a screen for ABA-insensitive mutants with altered ethylene production in Arabidopsis. A dominant allele of ABI4, abi4-152, which produces a putative protein with a 16-amino-acid truncation at the C-terminus of ABI4, reduces ethylene production. By contrast, two recessive knockout alleles of ABI4, abi4-102 and abi4-103, result in increased ethylene evolution, indicating that ABI4 negatively regulates ethylene production. Further analyses showed that expression of the ethylene biosynthesis genes ACS4, ACS8, and ACO2 was significantly decreased in abi4-152 but increased in the knockout mutants, with partial dependence on ABA. Chromatin immunoprecipitation–quantitative PCR assays showed that ABI4 directly binds the promoters of these ethylene biosynthesis genes and that ABA enhances this interaction. A fusion protein containing the truncated ABI4-152 peptide accumulated to higher levels than its full-length counterpart in transgenic plants, suggesting that ABI4 is destabilized by its C terminus. Therefore, our results demonstrate that ABA negatively regulates ethylene production through ABI4-mediated transcriptional repression of the ethylene biosynthesis genes ACS4 and ACS8 in Arabidopsis.