Control of fruit ripening, quality and yield is of major scientific, nutritional and commercial importance. The burst of ethylene (ET) production at the initiation of ripening is the most critical event controlling climacteric (CL) fruit ripening, yet little is known about how it is initiated. ABA is known to be capable of inducing ET production in many biological processes. However, the mechanism for this ABA induced ET production (AEP) and its potential importance in the burst of ET production that initiates ripening are unclear. Here, we report a branched signalling network involving ABA-activation of multiple SlSnRK2 (SNF1-related protein kinase 2) kinases, which, when overexpressed in tomato, stimulated ABA-induced ET production. Two key components, SlSnRK2.1 and SlSnRK2.4, phosphorylate an HD-Zip homeobox transcription factor, SlHB1, which transcriptionally activates ACC oxidase (SlACO1), required for ethylene synthesis. Concurrently, SlSnRK2.1 and SlSnRK2.4 phosphorylate two mitogen-activated protein kinases, SlMPK1/2, resulting in the post-translational stabilisation of ACC synthase (SlACS2), which generates the precursor 1-aminocyclopropane-1-carboxylic acid (ACC) that is converted to ET by ACO1. Removal of SlSnRK2.1 by CRISPR/Cas9 mutation was sufficient to alter the progress of fruit ripening. These results indicate that ABA is a primary hormonal signal modulating CL fruit ripening that stimulates ethylene production by targeting different steps in the ethylene biosynthesis pathway by both transcriptional and post-translational mechanisms. Further analysis revealed that removal of SlSnRK2.1 signalling also affected other aspects of the life cycle by prolonging the flowering period and suppressing seed development, indicating the potential for modifying fruit cropping and seedlessness.

Timely initiation of fruit ripening is crucial for improving agricultural efficiency and shelf life. While the progression of tomato ripening and the roles of ethylene and its core transcriptional controls are well established from the breaker (BR) stage onwards, the molecular mechanisms that fine-tune the transition from fruit development to ripening remain poorly understood. In this study, we identified a previously uncharacterized NAC transcription factor (TF), Ripening Accelerator (RAR), as a key negative modulator of climacteric ripening onset. In fruit, RAR is highly expressed at the mature green (MG) stage and downregulated at BR stage, preceding the climacteric ethylene burst. Silencing RAR via RNA interference significantly accelerated fruit ripening and ethylene production prior to BR stage, especially under high light conditions. RAR directly represses ACC Synthase 2 (ACS2), a key ethylene biosynthesis gene. Although RAR can form a heterodimer with the ripening-promoting NAC TF Non-Ripening (NOR), this heterodimer exhibits weaker transcriptional activation than the NOR homodimer, indicating a repressive effect of RAR on NOR-mediated activation. Moreover, RAR expression is negatively regulated by ethylene, forming a feedback loop that modulates the timing of ripening onset. Our findings uncover a previously unrecognized regulatory checkpoint in the ripening program, where RAR probably acts as a developmental safeguard to prevent premature ripening. Targeted manipulation of RAR offers a promising strategy for fine-tuning ripening onset and improve postharvest fruit quality across diverse environmental conditions.

ABSTRACT While direct‐seeded rice (DSR) offers a sustainable and resource‐efficient alternative to conventional puddled transplanting, its widespread adoption is severely constrained by the susceptibility of elite cultivars to anaerobic stress during germination, leading to poor crop establishment and substantial yield losses. To address this critical agricultural bottleneck, we conducted a comprehensive genetic evaluation of 96 rice genotypes, predominantly comprising traditional landraces from Tamil Nadu, India, to identify superior genetic donors and elucidate the molecular architecture underlying anaerobic germination (AG) tolerance. Phenotypic screening under controlled anaerobic conditions identified shoot and coleoptile elongation as key adaptive traits conferring survival advantage, with landraces Kudavazhai and Poongar demonstrating exceptional AG tolerance and representing invaluable genetic resources for future breeding initiatives. Genomewide association studies (GWASs) employing a high‐density 50 K SNP array revealed 50 significant marker–trait associations distributed across 21 linkage disequilibrium (LD) blocks spanning 11 chromosomes. The reliability of these associations is strongly supported by extensive colocalization with previously characterized quantitative trait loci (QTLs) for AG and related stress tolerance traits, including the major QTL qAG9 on chromosome 9, as well as QTLs controlling coleoptile length ( qCL6b ), mesocotyl development and root architectural traits ( QRSA‐4 , QRV‐4 ). These genomic regions harbour well‐characterized AG‐tolerance genes, most notably OsTPP7 , which facilitates gibberellic acid‐independent starch mobilization, along with genes encoding alcohol dehydrogenase (ADH) and the metallothionein OsMT2B , collectively confirming their essential roles in anaerobic metabolic adaptation. Our investigation revealed an extensive repertoire of novel candidate genes critical for hypoxic survival, including energy metabolism regulators (ADP‐glucose pyrophosphorylase, fructose‐6‐phosphate‐2‐kinase and beta‐glucosidase), hormone biosynthesis and signalling components (ACC synthase mediating ethylene production, galactinol synthase governing raffinose family oligosaccharide synthesis), cellular stress signalling and detoxification systems (calmodulin‐like proteins, calcineurin B‐like proteins orchestrating Ca 2+ ‐mediated responses, glutathione homeostasis regulators and superoxide dismutase) and polyamine biosynthesis enzymes (S‐adenosylmethionine decarboxylase). Haplotype analysis of critical LD blocks (1.1, 5.1 and 10.1) revealed functionally significant allelic variations that directly correlate with phenotypic performance. Notably, specific haplotypes of the calcineurin B‐like protein gene ( Os10g0564800 ) within LD block 10.1 exhibited strong correlation with differential shoot elongation capacity, establishing its function as a molecular switch in Ca 2+ ‐mediated stress response cascades involving the calcium‐dependent protein kinase CIPK15. These findings reinforce the complex polygenic architecture of AG tolerance, which is orchestrated through coordinated molecular networks integrating anaerobic fermentation pathways, carbohydrate mobilization systems, reactive oxygen species detoxification mechanisms and hormonal regulatory circuits. Through this integrated approach combining GWAS mapping, comprehensive candidate gene identification and functional haplotype analysis, we provide a detailed molecular framework to understand anaerobic germination tolerance, identify elite germplasm resources with superior adaptive capacity and deliver specific allelic targets to accelerate precision breeding of flood‐resilient, high‐yielding DSR varieties for sustainable rice production systems.

The early stages of plant–microbe interaction are critical for establishing beneficial symbioses. We investigated how the endophytic fungus Fusarium solani strain FsK modulates tomato (Solanum lycopersicum) development and hormone pathways during in vitro co-cultivation. Seedlings were sampled at three early interaction stages (pre-contact, T1; initial contact, T2, 3 days post-contact, T3). Root traits and root and leaf transcripts for abscisic acid (ABA) and ethylene (ET) pathways were quantified, alongside fungal ET-biosynthesis genes. FsK altered root system architecture, increasing root area, lateral root number, root-hair length, and fresh biomass. These morphological changes coincided with tissue- and time-specific shifts. In leaves, FsK broadly affected ABA biosynthetic and homeostasis genes (ZEP1, NCED1, ABA2, AAO1, ABA-GT, BG1), indicating reduced de novo synthesis with enhanced deconjugation of stored ABA. ET biosynthesis was curtailed in leaves via down-regulation of ACC oxidase (ACO1–3), with isoform-specific changes in ACC synthase (ACS). The ET receptor ETR1 was transiently expressed early (T1–T2). FsK itself showed staged activation of fungal ET-biosynthesis genes. These results reveal coordinated fungal–plant hormone control at the transcriptional level that promotes root development during early interaction and support FsK’s potential as a biostimulant.

Worldwide, 13.3% of food was wasted in 2020. Ethylene biosynthesis, responsible for fruit ripening, regulates key processes in plant growth and aging. Aptamers are DNA or RNA molecules with the capacity to bind with high affinity and specificity to proteins due to their three-dimensional structure. Therefore, conventional aptamer selection methods are often costly, inefficient, and time-consuming. In this context, in silico molecular docking offers an efficient alternative, enabling the evaluation of binding potential prior to experimental assays. This research identified aptamers with high predicted affinity for the 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) enzymes, essential in ethylene biosynthesis. Using ZDOCK for preliminary screening and HDOCK for refined analysis, aptamer-enzyme interactions were modeled. Aptamers AB451 and ABR6P.1 showed promising binding to ACC synthase, while RO33828 and O0O6O1 were optimal for ACC oxidase. These results represent a computational foundation for the development of aptamer-based inhibitors to potentially delay ripening and reduce postharvest losses. Experimental validation will be required to confirm their inhibitory function.

Related to APETALA2.1, an interacting protein of alcohol dehydrogenase 1, is crucial for the flooding-stress responses in Taxodium hybrids.

ABSTRACT Plant development and productivity are significantly hindered by salt stress, leading to substantial financial losses in the agriculture sector. Salinity stress negatively impacts the overall growth, physiology, and metabolism of plants. Specifically, NaCl stress is particularly harmful to tomato plants, causing suppression of seedling growth, accumulation of sodium (Na+) and chloride (Cl−) ions, disrupted ion homeostasis, reduced proline and chlorophyll content, and impairment of antioxidant enzyme systems. This research aimed to investigate the role of exogenous putrescine (PUT) application on tomato (Solanum lycopersicum L.) seedlings under NaCl stress (250 mm) to determine its potential protective effects. Various physio-biochemical attributes were estimated using precise protocols for NaCl-treated, PUT-treated, and untreated controlled tomato seedlings also analyzed for the expression of ACS1, NHX1, HKT1;2, and SOS1 genes. Additionally, ACC synthase activity, ethylene content, electrolyte leakage, proline content, Na+ and potassium (K+) ion content, lycopene content, and antioxidant enzyme activities were examined. Results indicated that PUT application enhanced the expression of ACS1, NHX1, HKT1;2, and SOS1 genes increase the ACC synthase activity, ethylene content, proline content, and Na+ and K+ ion content, while reducing electrolyte leakage. Furthermore, PUT application significantly increased the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR), as well as other morphological parameters. Overall, our research demonstrated the potential benefits of PUT applications for enhancing crop growth and improving salt stress tolerance, which are crucial for agronomy.

The gaseous hormone ethylene controls a variety of physiological processes in horticultural plants, including fruit ripening and elongation, flower development and senescence, and responses to stresses. The functions of ethylene in these processes are intimately linked to its precise biosynthesis, which is finely tuned by a complex network of positive and negative regulators. While significant progress has been made in understanding the roles of positive regulators in ethylene biosynthesis, the negative regulators of ethylene biosynthesis has only recently begun to receive more focus. Ethylene biosynthesis is a simple two-step reaction in land plants, committed by two dedicated enzymes, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) and ACC oxidase (ACO). Over the past decade, a growing number of research has identified a wide range of transcriptional, posttranscriptional and epigenetic negative regulators for ACS and/or ACO in horticultural plants, greatly enhancing our understanding of the intricate network that modulates ethylene production. In this review, we provide a comprehensive overview of the negative regulators that mediate ethylene biosynthesis in horticultural plants, with respect to their functions and molecular mechanisms, and their responses to external environmental stimuli or internal growth signals.

Improving nitrogen use efficiency (NUE) is one of the major objectives for crop breeding. As nitrate signaling plays pivotal roles in nitrogen use of plants, factors in this pathway might be valuable for improving the NUE of maize. In this research, we performed Gene Set Enrichment Analysis (GSEA) of maize transcriptomes in response to nitrate and found that the ethylene action pathway might participate in nitrate signaling. Through a modified reciprocal best hit approach, we obtained 16 maize aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) and four ACC synthase (ACS) homologs in maize genome. In silico analyses and the reverse transcription quantitative PCR assays demonstrated that ZmACCO7, ZmACCO5, ZmACCO15, ZmACCO35, and ZmACCO31 are the top five highly expressed ACO genes, and ZmACS1 is the most highly expressed ACS gene in the primary and seminal roots of maize. We discovered that ACO and ACS genes have different regulatory modes in response to nitrate provision. Some ACO genes, which are mainly expressed in root regions far from the root tip like ZmACCO7, are repressed by nitrate, while the others, which are mainly expressed in root regions near the root tip like ZmACCO5, are induced by nitrate. ZmACS1, which has more uniform expression across maize roots, is induced in root regions near the root tip and repressed in regions far from the root tip. A phenotypic analysis indicated that upregulation of ACO and ACS genes by nitrate is linked to repression of axial root elongation by nitrate while the downregulation of these genes is associated with the promotion of growth of lateral roots of the axial roots. In addition, differences in regulation of ACO and ACS genes by nitrate were observed between genotypes, which is related to the differences in the responses of their primary root growth to nitrate. These results suggested that the ethylene synthesis pathway is involved in the responses of maize roots to nitrate, which is associated with the remodeling of maize root architecture by nitrate.

This study evaluated the effectiveness of controlled atmosphere (CA) storage in preserving the post-harvest quality of peaches (Prunus persica), focusing on delaying ripening and extending shelf life. Peaches harvested 110 days after bloom were stored under CA conditions with reduced oxygen and elevated carbon dioxide at low temperatures. CA storage significantly suppressed internal and external discoloration, maintained fruit firmness, and reduced ethylene production, contributing to prolonged freshness and marketability. Physiological assessments revealed that CA storage slowed the decline in firmness, minimized weight loss, and controlled respiration and ethylene production, particularly at 10 °C. Transcriptome analysis identified approximately 1971 differentially expressed genes associated with CA storage. Among these, ethylene biosynthesis and signaling genes such as ACC synthase 1, ACC synthase 6, and ACC oxidase 1 were significantly downregulated under CA conditions, leading to the suppression of ethylene production. This reduction in ethylene biosynthesis likely played a critical role in delaying the ripening process during storage. As a result of the suppressed ethylene signaling, the expression of key cell wall-degrading enzymes, including polygalacturonase and pectate lyase family, was also notably reduced. This downregulation contributed to the maintenance of fruit firmness by minimizing enzymatic degradation of the cell wall. CA storage also modulates the activity of reactive oxygen species-related enzymes, enhancing fruit resistance to oxidative stress. These findings highlight the targeted benefits of CA storage in extending the shelf life of peaches by delaying ripening, maintaining fruit firmness, and reducing spoilage. This approach offers a scientifically supported strategy to minimize post-harvest losses and enhance economic returns in the horticultural industry.

In plants, developmental or environmental stresses activate a suite of different phytohormones that trigger biochemical and/or morphological adaptations. The gaseous phytohormone ethylene has a major effect on the plant life cycle from germination onward. Ethylene biosynthesis is tightly regulated by external and internal cues. In etiolated seedlings of Arabidopsis and rice, various phytohormones affect ethylene biosynthesis through transcriptional and/or post-transcriptional regulation of 1-aminocyclopropane-1-carboxylic acid (ACC), ACC synthases (ACS), and ACC oxidases (ACO). This study showed strigolactone also affected ethylene biosynthesis in dark-grown rice seedlings. Strigolactone treatment altered levels of S-ADENOSYLMETHIONINE SYNTHASES (OsSAMSs) and ACC SYNTHASES (OsACSs) transcripts, which encode enzymes involved in the initial steps of ethylene biosynthesis. The application of strigolactone reduced ethylene production, however, by decreasing transcription of OsACO genes, thus negatively affecting the final step of ethylene biosynthesis. In addition, treatment with strigolactone resulted in a phenotype in which the coleoptiles of dark-grown rice seedlings were shortened, contrary to treatment with ACC. These results reveal the tight correlation between strigolactone and ethylene biosynthesis.

In the climacteric fruit tomato (Solanum lycopersicum), 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 2 (ACS2) and ACS4 are jointly recognized as key enzymes in orchestrating System-2 ethylene biosynthesis during fruit ripening. However, the precise roles and individual contributions of ACS2 and ACS4 within this process remain elusive. Here, we generate acs2, acs4 single knockout, and acs2/4 double knockout mutants through the CRISPR/Cas9 system. Our results reveal that the knockout of ACS2 leads to a modest decrease in ethylene production, with minimal effects on fruit ripening. In contrast, the knockout of ACS4 unveils a severe ripening defect akin to that observed in the acs2/4 mutant, which stems from a profound disruption of ethylene autocatalytic biosynthesis, ultimately resulting in inadequate ethylene production vital for supporting fruit ripening. Transcriptome analysis, in conjunction with exogenous ethylene treatment, conclusively demonstrates a pronounced dose-dependent correlation between fruit ripening and ethylene, wherein varying doses of ethylene distinctly regulate the expression of a substantial number of ripening-related genes, eventually controlling both the ripening process and quality formation. These findings clarify the pivotal role of ACS4 in ethylene biosynthesis compared to ACS2 and deepen our understanding of the fine-tuned regulation of ethylene in climacteric fruit ripening.

1-Aminocyclopropane-1-carboxylate synthase (ACCS) catalyzes the conversion of S-adenosyl-methionine to 1-aminocyclopropane-1-carboxylate (ACC), a rate-limiting step in ethylene biosynthesis. A gene encoding a putative ACCS protein was identified in the human genome two decades ago. It has been shown to not exhibit any canonical ACC synthase activity and its true function remains obscure. In this study, through a biochemical profiling approach, we demonstrate that human ACCS possesses cysteine conjugate sulfoxide β-lyase activity. This function is unexpected but reasonable, as it somewhat parallels the activity of ACCS proteins found in non-seed plants. Structure-function relationship study of human ACCS, guided by an AlphaFold2 model, allowed us to identify key active site residues that are important for its β-lyase activity. Our biochemical study of human ACCS also provided insights into the function of other mammalian ACCS homologs.

Raspberry is a berry whose fruit is not tolerant to storage; breeding varieties with extended storage time and high comprehensive quality are significant for raspberries in cold regions. 1-Aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) is a limiting enzyme in the ethylene synthesis process, which plays essential roles in fruit ripening and softening in plants. In this study, the RiACS1 gene in raspberry (Rubus idaeus L.) variety ‘Polka’ was cloned. The RiACS1 gene overexpression vector was constructed and transformed into tomato plants using the Agrobacterium tumefaciens infection method to verify its function in their reproductive development. The RiACS1 gene, with a total length of 1476 bp, encoded a protein with 491 amino acids. The subcellular localization analysis of the RiACS1 protein in the tobacco transient expression system revealed that the RiACS1-GFP fusion protein was mainly located in the nucleus. Compared with the control, the flowering time and fruit color turning time of transgenic strains were advanced, and the fruit hardness was reduced. Overexpression of RiACS1 increased the activity of ACC synthase, ethylene release rate, and respiration rate during the transchromic phase. It changed the substance content, increased the content of vitamin C and anthocyanin in the fruit ripening process, and decreased the content of chlorophyll and titrable acid at the maturity stage. In addition, RiACS1 increased the relative expression levels of ethylene synthesis-related genes such as SlACS4, SlACO3, and SlACO1 in the fruit ripening process, while it decreased the expression levels of SlACS2 at the maturity stage. These results suggested that the RiACS1 gene could promote early flowering and fruit ripening in tomato plants. This study provided a basis for further modifying raspberry varieties using molecular biology techniques.

Ethylene, often referred as "death hormone" for its role in plant abscission, senescence, and fruit ripening, is a simple olefin gas and the first gaseous hormone discovered in plants. It also regulates seed germination, root and shoot growth, flower development, fruit ripening, and responses to biotic and abiotic stresses. Ethylene biosynthesis initiates with methionine converting enzymatically to S-adenosyl-L-methionine (SAM), then to 1-aminocyclopropane-1-carboxylic acid (ACC) by ACC synthase (ACS), and finally to ethylene via ACC oxidase (ACO). Its production is regulated at transcriptional, post-transcriptional, and post-translationallevels. Ethylene sensing depends onreceptors such as ETR1 and ERS1,located on the endoplasmic reticulum. When ethylene binds these receptors,CTR1becomes inactive, allowing EIN2 to relay signal to transcription factors EIN3/EIL1 and ERFs. As this pathway can interact with auxin, jasmonic acid, salicylic acid, abscisic acid, and gibberellins, itcoordinates plant growth and stress management. Ethylene affects root system architecture, particularly under varying phosphate availability, modifying root hair development to enhance nutrient uptake. It also shapes plant immunity by modifyingdefense response against biotic and abiotic challenges. Advances such as ethylene-sensitive fluorescent reporters, genomic and proteomic tools, and computational models have clarified many aspectsof ethylene signaling. However, key questionsremain, including the preciseactivation mechanism ofethylene receptors, details ofhormonal crosstalk, and post-translational modifications.

Ethylene is an important plant hormone whose production relies on the action of key enzymes, one of which is 1-aminocyclopropane-1-carboxylate synthase (ACS). There are three classes of ACS, which are all partially regulated by degradation through the ubiquitin-proteasome system (UPS), which regulates ethylene production. Arabidopsis has a single class III ACS, ACS7, but although it is known to be degraded by the 26S proteasome, the UPS proteins involved are poorly characterised. In this work, we used mass spectrometry to identify novel components of the ubiquitin system that may contribute to the regulation of ethylene biosynthesis via ACS7. We found two HECT-type ligases, UPL1 and UPL2, which regulate ACS7 stability. In vitro experiments showed that UPL1 and UPL2 E3 ligases directly control ACS7 turnover. In addition, increased ethylene levels were observed in UPL1- and UPL2-knockout plants in response to NaCl and NaCl+MG132 treatment, respectively. Under the same conditions, we observed increased ACS7 transcript levels in upl1 compared to WT plants under control and stress conditions, further confirming that UPL1 and UPL2 regulate ACS7-dependent ethylene production in response to stress. We used molecular modelling to predict ACS7 ubiquitylation sites and cell-free degradation assays to verify that lysine residues at positions 174, 238 and 384 regulate ACS7 protein stability. Overall, this study provides new insights into the regulation of ACS7 protein stability, and hence ethylene production, in plant growth and development and the response to stress.

Ethylene is involved in the response to P deficiency in some model plants such as Arabidopsis and rice, but its role in wheat remains unclear. Following our recent study demonstrating the role of differentially expressed genes encoding ethylene response factors (ERFs) in response to P starvation in wheat, this study aims to investigate remodeling of the ethylene pathway and the physiological roles of ethylene in wheat under P deficiency using transcriptome analysis and the addition of the exogenous ethylene analogue, ethephon, or ethylene inhibitors. ERFs with at least a 2-fold expression change upon P deficiency had a distribution biased towards chromosome 4B. A group of genes encoding aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase were up-regulated under P starvation, suggesting an increase in ACC and ethylene content, which was verified by biochemical measurements and gas chromatography-mass spectrometry analysis. Under P deficiency, both root and shoot biomass decreased with application of exogenous ethephon or ethylene inhibitors, while root fork numbers and root surface area decreased upon ethephon treatment. Phosphate (Pi) concentrations in roots and old leaves increased with ethephon treatment, and Pi redistribution in roots and younger leaves was altered under Pi starvation. Our findings can guide breeding of germplasm with high Pi efficiency.

Constitutive expression of cucumber CsACS2 in Arabidopsis disrupts anther dehiscence and male fertility via ethylene signaling and DNA methylation, revealing new avenues for enhancing crop reproductive traits. The cucumber gene CsACS2, encoding ACC (1-aminocyclopropane-1-carboxylic acid) synthase, plays a pivotal role in ethylene biosynthesis and sex determination. This study investigates the effects of constitutive CsACS2 expression in Arabidopsis thaliana on anther development and male fertility. Transgenic Arabidopsis plants overexpressing CsACS2 exhibited male sterility due to inhibited anther dehiscence, which was linked to suppressed secondary cell wall thickening. RNA-Seq analysis revealed upregulation of ethylene signaling pathway genes and downregulation of secondary cell wall biosynthesis genes, with gene set enrichment analysis indicating the involvement of DNA methylation. Rescue experiments demonstrated that silver nitrate (AgNO₃) effectively restored fertility, while 5-azacytidine (5-az) partially restored it, highlighting the roles of ethylene signaling and DNA methylation in this process. Constitutive CsACS2 expression in Arabidopsis disrupts anther development through ethylene signaling and DNA methylation pathways, providing new insights into the role of ethylene in plant reproductive development and potential applications in crop improvement.

Ethylene is widely recognized as a positive regulator of leaf senescence. However, how plants coordinate the biosynthesis of ethylene to meet the requirements of senescence progression has not been determined. The rate-limiting enzyme in the ethylene biosynthesis pathway is ACC synthase. AtACS7 was previously considered one of the major contributors to the synthesis of "senescence ethylene" in Arabidopsis. However, the "brake signal" that fine-tunes the expression of AtACS7 to ensure optimal ethylene production during leaf development has yet to be identified. In the present study, the RING-H2 zinc-finger protein RIE1 was found to specifically interact with and ubiquitinate AtACS7, among all functional ACSs in Arabidopsis, to promote its degradation. Overexpression of RIE1 markedly decreased ethylene biosynthesis and delayed leaf senescence, whereas loss of function of RIE1 significantly increased ethylene emission and accelerated leaf senescence. The ethylene-related phenotypes of RIE1 overexpressing or knockout mutants were effectively rescued by the ethylene precursor ACC or the competitive inhibitor of ACS, respectively. In particular, AtACS7-induced precocious leaf senescence was strongly enhanced by the loss of RIE1 but was significantly attenuated by the overexpression of RIE1. The specific regions of interaction between AtACS7 and RIE1, as well as the major ubiquitination sites of AtACS7, were further investigated. All results demonstrated that RIE1 functions as an important modulator of ethylene biosynthesis during leaf development by specifically targeting AtACS7 for degradation, thereby enabling plants to produce the optimal levels of ethylene needed.

Application of nanoparticles blue-TiO2-x and chitosan coating to delay ripening and suppress ethylene-related gene expression of Cavendish banana