Flower Senescence Research Articles

Integration of Genome-Wide Identification and Transcriptome Analysis of Class III Peroxidases in Paeonia ostii: Insight into Their Roles in Adventitious Roots, Heat Tolerance, and Petal Senescence

As a plant-specific gene family, class III peroxidases (PODs) play an important role in plant growth, development, and stress responses. However, the POD gene family has not been systematically studied in Paeonia ostii. In this study, a total of 57 PoPOD genes were identified in the P. ostii genome. Subsequently, phylogenetic analysis and chromosome mapping revealed that PoPODs were classified into six subgroups and were unevenly distributed across five chromosomes. The gene structure and conserved motifs indicated the potential for functional divergence among the different subgroups. Meanwhile, four PoPODs were identified as tandem duplicated genes, with no evidence of segmental duplication. Using RNA-seq data from eight different tissues, multiple PoPODs exhibited enhanced expression in apical and adventitious roots (ARs). Next, RNA-seq data from AR development combined with trend analysis showed that PoPOD30/34/43/46/47/57 are implicated in the formation of ARs in tree peony. Through WGCNA based on RNA-seq, two key genes, PoPOD5/15, might be involved in heat tolerance via ABA and MeJA signaling. In addition, real-time quantitative PCR (qRT-PCR) analysis indicated that PoPOD23 may play an important role in flower senescence. These findings deepened our understanding of POD-mediated AR development, heat tolerance, and petal senescence in tree peony.

The histone deacetylase RhHDA15 represses petal senescence by epigenetically regulating reactive oxygen species homeostasis in rose.

Epigenetic modifications play vital roles in many biological processes. Flower senescence involves epigenetic factors that influence the chromatin state and gene expression. However, the molecular mechanism underlying the role of histone deacetylation in regulating flower senescence has not been elucidated. Here, we demonstrate that histone deacetylation is involved in flower senescence by fine-tuning reactive oxygen species (ROS) homeostasis in rose (Rosa hybrida). Our data reveal that the histone lysine deacetyltransferase RhHDA15 inhibits ROS accumulation and petal senescence by downregulating the expression of NADPH OXIDASE/RESPIRATORY BURST OXIDASE HOMOLOG (RhRboh) genes. Furthermore, the transcription factor RELATED TO ABI3/VP1 2 (RhRAV2) recruits RhHDA15 and the co-repressor TOPLESS (RhTPL) to suppress flower senescence by reducing H3 lysine 9 acetylation (H3K9ac) at the RhRbohA1/2 promoter and thus directly inhibiting precocious RhRbohA1/2 expression. Our work sheds light on an epigenetic mechanism in which histone deacetylation plays a crucial role in controlling petal senescence by precisely fine-tuning ROS homeostasis, providing insights into the regulatory network of organ senescence.

Exogenous nitric oxide extends longevity in cut Lilium tigrinum flowers by orchestrating biochemical and molecular aspects.

Senescence represents a developmentally orchestrated and precisely regulated cascade of events, culminating in the abscission of plant organs and ultimately leading to the demise of the plant or its constituent parts. In this study, we observed that senescence in cut Lilium tigrinum flowers is induced by elevated ABA levels and the hyperactivation of lipoxygenase (LOX) activity. This cascade increased ROS concentrations, heightened oxidative damage, and disrupted cellular redox equilibrium. This was evidenced by elevated lipid peroxidation, attenuated antioxidant machinery, and reduced membrane stability index (MSI). Despite its known role in delaying flower senescence, the specific biochemical and molecular mechanisms by which nitric oxide (NO) regulates senescence in cut L. tigrinum flowers are not fully elucidated. Specifically, the interactions between NO signaling and ABA metabolism, the regulation of protease activity, and the influence of NO-mediated ROS scavenging, senescence-associated gene expression requires further exploration. Exogenous application of sodium nitroprusside (SNP), a source of NO, mitigated senescence in L. tigrinum cut flowers by upregulating the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and reducing the LOX activity, an indicator of lipid peroxidation. SNP treatment also downregulated the relative expression of senescence-associated gene (SAG12 ),lipoxygenase 1 (LOX1 ), and abscisic aldehyde oxidase 3 (AAO3 ). NO also upregulated defender against apoptotic death 1 (DAD1 ) expression correlated with minimized protease activity and reduced α-amino acid content in SNP-treated tepals. This regulation was accompanied by increased contents of sugars, proteins and phenols and reduced abscisic acid content, which collectively delayed the senesecence and enhanced the longevity of L. tigrinum cut flowers. This study demonstrates that exogenous SNP application can effectively mitigate senescence in cut L. tigrinum flowers by modulating antioxidant enzyme activities, reducing oxidative stress, and regulating the expression of key senescence-associated genes. This study unravels the complex molecular networks involved in NO-mediated senescence delay, which may lead to the development of innovative approaches for improving flower longevity.

Nanochitosan-encapsulated melatonin: an eco-friendly strategy to delay petal senescence in cut gerbera flowers

BackgroundThe preservation of cut flowers, particularly Gerbera jamesonii, is crucial for maintaining their aesthetic value and extending vase life in the floriculture industry. To address this challenge, this study investigated the effects of melatonin (Mel) and encapsulated melatonin with nanochitosan (nCS-Mel) as preservative solutions on cut Gerbera jamesonii cv. ‘Terra kalina’ flowers. In research, we examined various physiological and biochemical parameters, including relative water content, membrane stability index, carbohydrate content, and antioxidant enzyme activities, to evaluate the efficacy of these treatments in prolonging the vase life and quality of cut gerbera flowers under controlled environmental conditions.ResultsOur results demonstrated that cut Gerbera jamesonii flowers maintained in vase solutions containing 0.1 and 0.5 mM nCS-Mel exhibited enhanced preservation of cell membrane integrity and anthocyanin content, while also maintaining higher levels of carbohydrates and total flavonoids in petals at the conclusion of their vase life. A decline in petal relative water content and protein levels was observed concomitantly with petal senescence, whereas total phenolic compounds showed an increase. The hydrogen peroxide (H2O2) content in petals exhibited an upward trend during vase life in control specimens, but this effect was mitigated in treatments containing melatonin. Although malondialdehyde (MDA) content generally increased throughout the vase life period, flowers subjected to either Mel or nCS-Mel treatments displayed reduced MDA accumulation. The activity of catalase (CAT) demonstrated an increasing trend during vase life, with the maximum activity observed in Gerbera flowers treated with 0.1 mM nCS-Mel. A similar upward trend was noted for superoxide dismutase (SOD) activity, with flowers in 0.5 mM nCS-Mel treatment exhibiting peak SOD values on day 12 relative to control and other treatments. Peroxidase (POD) activity also increased across all treatments, with particularly pronounced effects in vase solutions containing 0.1 mM Mel and nCS-Mel. Notably, flowers placed in vase solutions containing 0.1 mM nCS-Mel, followed by 0.5 mM nCS-Mel and 0.1 mM Mel, exhibited the most prolonged vase life, extending up to 12, 10.66, and 10.33 days, respectively, under room temperature conditions.ConclusionsThe application of nanoencapsulated melatonin as a vase solution for cut Gerbera jamesonii flowers demonstrates significant potential in extending vase life and maintaining flower quality through enhanced preservation of cellular integrity, antioxidant activity, and biochemical parameters. This innovative approach not only outperforms conventional treatments but also presents a more environmentally friendly alternative to traditional antimicrobial preservatives and sugars, offering a promising solution for the floriculture industry to improve cut flower longevity and reduce ecological impact.

Chemical-sensitized MITOGEN-ACTIVATED PROTEIN KINASE 4 provides insights into its functions in plant growth and immunity.

Two mitogen-activated protein kinase (MAPK) cascades with MPK4 and MPK3/MPK6 as the bottommost kinases are key to plant growth/development and immune signaling. Disruption of the MPK4 cascade leads to severe dwarfism and autoimmunity, complicating the study of MPK4 in plant growth/development and immunity. In this study, we successfully rescued the Arabidopsis (Arabidopsis thaliana) mpk4 mutant using a chemical-sensitized MPK4 variant, MPK4YG, creating a conditional activity-null mpk4 mutant named MPK4SR (genotype: PMPK4:MPK4YG mpk4) that could be used to examine the functions of MPK4 in plant growth/development and immunity. We discovered that the duration of the loss of MPK4 activity is important to plant immune responses. Short-term loss of MPK4 activity did not impact flg22-induced ROS burst or resistance against Pseudomonas syringae (Pst). Enhanced Pst resistance was only observed in the MPK4SR plants with stunted growth following prolonged inhibition of MPK4 activity. Transcriptome analyses in plants with short-term loss of MPK4 activity revealed a vital role of MPK4 in regulating several housekeeping processes, including mitosis, transcription initiation, and cell wall macromolecule catabolism. Furthermore, the constitutive weak activation of MPK4GA in the MPK4CA plants (genotype: PMPK4:MPK4GA mpk4) led to early flowering and premature senescence, which was associated with its compromised resistance against Pst. These findings suggest that MPK4 plays important roles in plant growth and development and in maintaining the delicate balance between growth/development and immune adaptation in plants.

Haplotype-resolved genome assembly and resequencing provide insights into the origin and breeding of modern rose.

Modern rose (Rosa hybrida) is a recently formed interspecific hybrid and has become one of the most important and widely cultivated ornamentals. Here we report the haplotype-resolved chromosome-scale genome assembly of the tetraploid R. hybrida 'Samantha' ('JACmantha') and a genome variation map of 233 Rosa accessions involving various wild species, and old and modern cultivars. Homologous chromosomes of 'Samantha' exhibit frequent homoeologous exchanges. Population genomic and genomic composition analyses reveal the contributions of wild Rosa species to modern roses and highlight that R. odorata and its derived cultivars are important contributors to modern roses, much like R. chinensis 'Old Blush'. Furthermore, selective sweeps during modern rose breeding associated with major agronomic traits, including continuous and recurrent flowering, double flower, flower senescence and disease resistance, are identified. This study provides insights into the genetic basis of modern rose origin and breeding history, and offers unprecedented genomic resources for rose improvement.

Classification of Vase Life Day Based on Petal Colorimetric Data in Cut Lisianthus Using AutoML

This study investigated the potential of petal colorimetric data to classify vase life stages in cut lisianthus flowers (Eustoma grandiflorum). We analyzed the changes in the petal color space over time, focusing on the b* value as an indicator of senescence due to increasing yellowing caused by copigmentation. A comparative analysis was conducted between two cultivation methods: soil (S) and hydroponic (H) cultivation. The objective was to evaluate the performance of machine learning models trained to classify vase life stages based on petal color data. Automated machine learning models exhibited better performance in H-cultivated cut flowers, effectively distinguishing days within the vase life stages from Days 1 to 14 for H cultivation. Cut flowers cultivated under S conditions showed less variation in the color space from Days 1 to 9, maintaining a relatively uniform color range. This made it more difficult to distinguish the vase life stages compared to H cultivation. These findings demonstrate that petal color metrics can serve as reliable indicators of cut flower senescence and potentially facilitate nondestructive methods for classifying vase life stages. This technology holds promise for wider applications in the floriculture industry, improving quality control, and extending the vase life of various cut-flower crops.

Dynamic aromatics: Evaluating fragrance quality shifts and implementation of real-time rapid detection in Hedychium cut flowers during senescence

The postharvest fragrance quality of aromatic cut flowers is crucial, yet efficient and rapid detection methods are lacking. To develop a rapid and accurate method for evaluating the fragrance quality during the senescence of aromatic cut flowers, this study first utilized HS–SPME–GC–MS to analyze the fragrance of six Hedychium cultivars cut flowers at different stages postharvest (bud, semi-open, full bloom, and senescence), identifying 69 compounds. Multivariate statistical analysis revealed significant during full bloom, with monoterpenoids predominant in ‘ZS’, ‘EM’, ‘Gaoling’, and ‘Jin’, and benzenoids/phenylpropanoids in ‘MH’. Concurrently, PTR–ToF–MS detected 68 masses consistent with GC–MS results. PLS–DA analysis identified eucalyptol, benzyl acetate, linalool, (E)-β-ocimene, methyl benzoate, and masses m/z 91.057, m/z 137.134, m/z 81.07, m/z 102.096, m/z 31.019 as potential markers for distinguishing Hedychium varieties. Additionally, PLS analysis identified masses m/z 58.078, m/z 103.076, and m/z 155.144 as predictors of agarospirol content; m/z 73.065, m/z 74.069, m/z 151.151 for eucalyptol, and m/z 27.021, m/z 31.019, m/z 41.039, m/z 43.054, m/z 55.054, m/z 57.033, m/z 70.077, m/z 72.056, m/z 88.079, m/z 91.057, m/z 92.065, and m/z 108.089 for benzyl acetate. The results provide new methods for efficient fragrance evaluation during the postharvest senescence of aromatic flower.

Analysis of the Aging-Related AP2/ERF Transcription Factor Gene Family in Osmanthus fragrans.

Ethylene-Responsive Factor (ERF) is a key element found in the middle and lower reaches of the ethylene signal transduction pathway. It is widely distributed in plants and plays important roles in plant growth and development, hormone signal transduction, and various stress processes. Although there is research on AP/ERF family members, research on AP2/ERF in Osmanthus fragrans is lacking. Thus, in this work, AP2/ERF in O. fragrans was extensively and comprehensively analyzed. A total of 298 genes encoding OfAP2/ERF proteins with complete AP2/ERF domains were identified. Based on the number of AP2/ERF domains and the similarity among amino acid sequences between AP2/ERF proteins from A. thaliana and O. fragrans, the 298 putative OfAP2/ERF proteins were divided into four different families, including AP2 (45), ERF (247), RAV (5), and SOLOIST (1). In addition, the exon-intron structure characteristics of these putative OfAP2/ERF genes and the conserved protein motifs of their encoded OfAP2/ERF proteins were analyzed, and the results were found to be consistent with those of the population classification. A tissue-specific analysis showed the spatiotemporal expression of OfAP2/ERF in the stems and leaves of O. fragrans at different developmental stages. Specifically, 21 genes were not expressed in any tissue, while high levels of expression were found for 25 OfAP2/ERF genes in several tissues, 60 genes in the roots, 34 genes in the stems, 37 genes in young leaves, 34 genes in old leaves, 32 genes in the early flowering stage, 18 genes in the full flowering stage, and 37 genes in the late flowering stage. Quantitative RT-PCR experiments showed that OfERF110a and OfERF110b had the highest expression levels at the full-bloom stage (S4), and this gradually decreased with the senescence of petals. The expression of OfERF119c decreased first and then increased, while the expression levels of OfERF4c and OfERF5a increased constantly. This indicated that these genes may play roles in flower senescence and the ethylene response. In the subsequent subcellular localization experiments, we found that ERF1-4 was localized in the nucleus, indicating that it was expressed in the nucleus. In yeast self-activation experiments, we found that OfERF112, OfERF228, and OfERF23 had self-activation activity. Overall, these results suggest that OfERFs may have the function of regulating petal senescence in O. fragrans.

Arabidopsis WRKY1 promotes monocarpic senescence by integrative regulation of flowering, leaf senescence, and nitrogen remobilization

Monocarpic senescence, characterized by whole-plant senescence following a single flowering phase, is widespread in seed plants, particularly in crops, determining seed harvest time and quality. However, how external and internal signals are systemically integrated into monocarpic senescence remains largely unknown. Here, we report that the Arabidopsis thaliana transcription factor WRKY1 plays essential roles in multiple key steps of monocarpic senescence. WRKY1 expression is induced by age, salicylic acid (SA), and nitrogen (N) deficiency. Flowering and leaf senescence are accelerated in the WRKY1 overexpression lines but are delayed in the wrky1 mutants. The combined DNA affinity purification sequencing and RNA sequencing analyses uncover the direct target genes of WRKY1. Further studies show that WRKY1 coordinately regulates three processes in monocarpic senescence: (1) suppressing FLOWERING LOCUS C gene expression to initiate flowering, (2) inducing SA biosynthesis genes to promote leaf senescence, and (3) activating the N assimilation and transport genes to trigger N remobilization. In summary, our study reveals how one stress-responsive transcription factor, WRKY1, integrates flowering, leaf senescence, and N remobilization processes into monocarpic senescence, providing important insights into plant lifetime regulation.

Foliar application of agrochemicals enhance growth, productivity, quality and biochemical traits of soybean

Flower drop, senescence of flowers and inadequate pod filling pose significant challenges in soybean cultivation as rapid nutrient extraction from leaves during the reproductive stage accelerates leaf aging. The present study assessed the effect of foliar application of agrochemicals on growth, productivity, quality and biochemical traits of soybean at two locations during kharif (rainy) season of 2021 and 2022. The experiment comprised of ten treatments of foliar application of agrochemicals [absolute control, water spray, potassium nitrate (KNO3) 1.5%, NPK (19:19:19) 1.5%, boron 0.3%, ammonium molybdate (AM) 0.5%, thiourea 750 parts per million (ppm), urea 2.0%, muriate of potash (MOP) 0.5% and salicylic acid (SA) 100 ppm] at flower and pod initiation stages along with the recommended dose of fertilizer (RDF) in a randomized complete block design replicated thrice. Results revealed that foliar application of boron 0.3%, urea 2.0% and MOP 0.5% at Ludhiana and MOP 0.5%, potassium nitrate 1.5% and urea 2.0% at Ballowal Saunkhri increased growth (plant height and dry matter accumulation), yield attributes (number of pods plant−1, number of filled pods plant−1 and 100-seed weight) and seed yield. These agrochemicals showed positive effects on the biochemical parameters with increased levels of proline and total phenol content as well as improvements in total soluble sugars, starch and protein content. The findings suggest that foliar application of agrochemicals (boron 0.3%, urea 2.0%, MOP 0.5% and potassium nitrate 1.5%) along with RDF can improve soybean growth and seed yield by mitigating the nutrient stress at reproductive stages.

PhERF71 regulates petunia flower senescence by modulating ethylene biosynthesis

Ethylene, an endogenous hormone, commonly promotes flower senescence, but the molecular regulatory mechanisms underlying ethylene-induced flower senescence remain elusive. In this study, we describe an ethylene-responsive element binding factor, PhERF71, which affects flower senescence in petunia (Petunia hybrida). PhERF71 was up-regulated in senescing petunia flowers and after exogenous ethylene treatment, but silver thiosulfate (STS), an ethylene inhibitor, treatment decreased PhERF71 transcripts. Transient silencing of PhERF71 delayed petunia flower senescence, and reduced the transcription of senescence-associated gene 12 (PhSAG12). PhERF71-RNAi transgenic plants showed prolonged flower longevity, and PhERF71-overexpressing plants displayed shortened flower longevity, compared with wild-type (WT) plants. Electrolyte leakage rates and expression levels of PhSAG12 were lower in PhERF71-RNAi plants but higher in PhERF71-overexpressing plants. Silencing or overexpression of PhERF71 influenced the accumulation of ethylene, gibberellin (GA3), and abscisic acid (ABA), and the effect on ethylene accumulation was earlier than that on ABA and GA3. Ethylene treatment restored the delayed flower senescence to WT levels in PhERF71-silenced plants. Silencing of PhERF71 reduced expression levels of several ethylene biosynthetic genes, including 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 4 (PhACS4), PhACS6, and ACC oxidase 4 (PhACO4), while overexpression of PhERF71 imposed the opposite effect on their expression levels. Dual luciferase assay showed that PhERF71 directly bound to the promoters of PhACS4 and PhACO4, and transient silencing of PhACS4 and PhACO4 delayed flower senescence. Our results suggest that PhERF71 is a positive regulator of flower senescence by promoting ethylene biosynthesis.

Deciphering the auxin-ethylene crosstalk in petal abscission through auxin influx carrier IpAUX1 of Itoh peony ‘Bartzella’

Auxin gradient on either side of the abscission zone play a crucial role in regulating organ abscission during plant senescence. Yet, the impact of auxin on the opening and senescence of cut peony flowers, specifically Itoh peony ‘Bartzella’, remains elusive. We employed the frozen section method to investigate the cell morphology within the petal abscission zone. Additionally, we quantified auxin levels via enzyme immunoassay and assessed the expression of genes related to indole-3-acetic acid (IAA) levels. Through our analyses, we pinpointed the critical gene, IpAUX1. Further investigation of IpAUX1 involved virus-induced gene silencing (VIGS) and transient overexpression techniques, allowing us to assess its role both in vitro flowers, through vacuum application, and in vivo flowers, via injection. Significant alterations were observed in the structure and cell morphology of the abscission zone correlating with the process of petal abscission, alongside noticeable auxin gradient. Silencing IpAUX1 led to a noticeable delay in petal abscission for both in vitro flowers and vivo flowers, while its transient overexpression hastened this process. This silencing effect was accompanied by a reduction in IAA levels around the abscission zone and a subsequent delay in the erasure of the auxin gradient. It also resulted in the downregulation of several genes: the auxin response factor IpARF1, ethylene synthesis-related genes IpACS1 and IpACO1, and cell wall hydrolysis-related genes IpPME1 and IpPG1. Conversely, the expression of genes involved in auxin synthesis gene IpYUCCA10, auxin efflux carrier IpPIN1, and the ethylene receptor IpETR1 saw significant upregulation. This study concludes that the auxin influx carrier IpAUX1 enhances the abscission zone cells' responsiveness to ethylene by modulating the auxin gradient. This action promotes cell hydrolysis within the abscission zone, thereby encouraging petal abscission. Our findings underscore the pivotal role of IpAUX1 as a positive regulator during the process of petal abscission.

Signalling cascades choreographing petal cell death: implications for postharvest quality.

Senescence is a multifaceted and dynamic developmental phase pivotal in the plant's lifecycle, exerting significant influence and involving intricate regulatory mechanisms marked by a variety of structural, biochemical and molecular alterations. Biochemical changes, including reactive oxygen species (ROS) generation, membrane deterioration, nucleic acid degradation and protein degradation, characterize flower senescence. The progression of senescence entails a meticulously orchestrated network of interconnected molecular mechanisms and signalling pathways, ensuring its synchronized and efficient execution. Within flowering plants, petal senescence emerges as a crucial aspect significantly impacting flower longevity and postharvest quality, emphasizing the pressing necessity of unravelling the underlying signalling cascades orchestrating this process. Understanding the complex signalling pathways regulating petal senescence holds paramount importance, not only shedding light on the broader phenomenon of plant senescence but also paving the way for the development of targeted strategies to enhance the postharvest longevity of cut flowers. Various signalling pathways participate in petal senescence, encompassing hormone signalling, calcium signalling, protein kinase signalling and ROS signalling. Among these, the ethylene signalling pathway is extensively studied, and the manipulation of genes associated with ethylene biosynthesis or signal transduction has demonstrated the potential to enhance flower longevity. A thorough understanding of these complex pathways is critical for effectively delaying flower senescence, thereby enhancing postharvest quality and ornamental value. Therefore, this review adopts a viewpoint that combines fundamental research into the molecular intricacies of senescence with a practical orientation towards developing strategies for improving the postharvest quality of cut flowers. The innovation of this review is to shed light on the pivotal signalling cascades underpinning flower senescence and offer insights into potential approaches for modulating these pathways to postpone petal senescence in ornamental plants.

Nano Silver and melatonin effectively delay the senescence of cut carnation flowers under simulated vibrational stress

ABSTRACT Carnation (Dianthus caryophyllus L.) holds great significance as a cut flower, and its vase life plays a crucial role in determining its quality and market appeal. However, the extended transportation distances from the production location to consumer markets can have an unfavourable impact on the vase life and overall quality of cut flowers. The first experiment demonstrated that exposing cut carnation flowers to simulated vibrational stress (SVS) led to a decline in vase life and overall quality. Notably, the application of Nano Silver (NS; 25 and 50 μM) and melatonin (MT; 100 and 200 μM) into the holding solution proved effective in counteracting these negative effects, and extended the vase life by promoting cut flower water relations. In the second experiment, the optimal concentrations of NS and MT into the holding solution (25 and 100 μM, respectively) effectively reduced chlorophyll degradation, electrolyte leakage, and lipid peroxidation by enhancing the activity of catalase and peroxidase enzymes. As a result, it appears that the application of NS and MT in the holding solution has successfully prolonged vase life by both improving water balance and boosting antioxidant activity, while mitigating the negative effects of SVS.

Evolutionary and Integrative Analysis of the Gibberellin 20-oxidase, 3-oxidase, and 2-oxidase Gene Family in Paeonia ostii: Insight into Their Roles in Flower Senescence

The brief longevity of tree peony blossoms constrains its ornamental value and economic worth. Gibberellins (GAs) are crucial in the modulation of flower senescence, and GA 20-oxidase (GA20ox), GA 3-oxidase (GA3ox), and GA 2-oxidase (GA2ox) catalyze the synthesis and deactivation of bioactive GAs. In Paeonia ostii, a total of three PoGA20ox, ten PoGA3ox, and twelve PoGA2ox proteins were identified and comprehensively analyzed. The analysis of the gene structures, conserved domains, and motifs revealed structural similarities and variances among the GA20ox, GA3ox, GA2ox-A, and GA2ox-B subfamilies. The synteny analysis indicated a scarcity of collinear blocks within the P. ostii genome, with no tandem or whole-genome duplication/segmental duplications found in PoGAoxs. The investigation into the binding of transcription factors to PoGAox promoters and the assessments of the expression levels suggest that PoGA2ox1 and PoGA2ox8.1 are promising candidate genes implicated in the regulation of floral senescence. Further, Pos.gene61099 (BPC6) and Pos.gene61094 (CIL2) appear to modulate PoGA2ox1 transcription in a positive and negative manner, respectively, while Pos.gene38359 (DDF1) and Pos.gene17639 (DREB1C) likely enhance PoGA2ox8.1’s expression. This study lays a foundation for an in-depth understanding of PoGAox functions and the development of strategies to delay flower senescence in tree peony.

Genome-Wide Identification of Osmanthus fragrans Histone Modification Genes and Analysis of Their Expression during the Flowering Process and under Azacytidine and Ethylene Treatments

Histone acetylation and methylation, governed by various histone modification (HM) gene families, are vital for plant biological processes. However, there are limited studies that have explored HMs in ornamental horticultural trees, including sweet osmanthus (Osmanthus fragrans). We performed genome-wide search and identified 208 OfHMs, encompassing 81 histone methyltransferases (OfHMTs), 51 histone demethylases (OfHDMs), 49 histone acetyltransferases (OfHATs) and 27 histone deacetylases (HDACs). Our comprehensive analysis covered chromosome locations, gene structures, conserved domains, cis-acting elements, phylogenetic comparisons, protein interaction networks and functional enrichment pathways for these gene families. Additionally, tandem and fragment replications were unveiled as contributors to the expansion of OfHMs, with some genes exhibiting positive selection. Furthermore, we examined OfHM expression profiles across various tissues and flowering stages, and under 5′-azacytidine (Aza) and ethylene treatments. Most OfHMs displayed heightened expression in leaves, and were downregulated during the flower opening and senescence stages, including OfPRMTs, OfHDTs, OfHDAs, OfSRTs, OfJMJs and OfHAGs; 75.86% and 80.77% of the differentially expressed OfHMs were upregulated after Aza and ethylene treatments, including OfHAGs, OfHDAs and OfSDGs. This study offers a comprehensive analysis of the OfHM gene family, which indicated their potential involvement in ethylene and Aza responses, and in the flowering process. These findings provide valuable insights into the role of OfHMs in flowering and stress responses.

Two key enzyme genes associated with ethylene bio-synthesis, LbACS and LbACO, are involved in the regulation of lily flower senescence

Ethylene plays an important role in regulating the growth and development of flowers and determines the flower life span of ornamental plants. In this study, the lily variety 'Manissa' was used to elucidate the mechanism associated with the regulation of lily senescence by the genes for 1-aminocyclopropane-1-carboxylic acid synthetase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), which are key enzymes in the ethylene biosynthesis pathway. The results showed that ethylene release increased, the relative water content first increased and then decreased, and relative conductivity continuously increased as lily bud development progressed. LbACS1 transcription was highest at the blooming stage, LbACS7 transcription was highest at the green bud stage, and LbAC03 and LbAC04 levels both peaked at the yellow bud stage and the blooming stage. After treating cut lily flowers with ethephon and ethylene inhibitor 1-methylcyclopropene (1-MCP), the results showed that ethephon promoted the senescence of cut flowers, ethylene release, and the transcription levels of the four Lb genes. 1-MCP treatment also delayed the aging of cut flowers, but reduced ethylene release and inhibited the transcription of LbAC03 and LbAC04 when the treatment was applied during the later stages of bud development. This study provided evidence for the role of ethylene and the functions of LbACS and LbAC0 in the aging process associated with cut lily flowers.

Physico-Chemical Responses of Alstroemeria spp. cv. Rebecca to the presence of Salicylic Acid and Sucrose in vase solution during postharvest life.

The primary challenge in the cut flower industry, specifically in the postharvest phase, is the short vase life of flowers. This issue, along with early leaf yellowing and perianth abscission, significantly diminishes the economic value of flowers due to their accelerated senescence. To tackle this, we conducted a factorial experiment on Alstroemeria cv. Rebecca, utilizing a completely randomized design with three replications. In this experiment the effects of varying concentrations of Salicylic acid (SA) (0, 1.5, and 3mM) and sucrose (SU) (0% and 3%) were investigated on the postharvest quality of leaves and florets, with systematic evaluations every three days throughout their vase life. This experiment revealed that the specific treatment combination of 1.5mM SA + 3% SU (T5) markedly improved various parameters, such as vase life, total chlorophyll content, membrane stability index, relative fresh weight, and water uptake of cut flowers. In our analysis, we observed that this preservative solution not only extended the vase life and enhanced water uptake but also effectively preserved total chlorophyll, mitigated the loss of fresh weight, and reduced membrane deterioration in petals. Additionally, our results showed an increase in the activities of catalase (CAT) and peroxidase (POD) enzymes, as well as total protein content, alongside a decrease in malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels. Moreover, this study noted a decrease in microbial populations in solutions containing different concentrations of salicylic acid. Our research demonstrated that alstroemeria flowers maintained in a solution with 1.5mM SA + 3% SU exhibited a significantly prolonged vase life of up to 21days, in contrast to the 15days observed in control flowers kept in water. These results are highly beneficial for manufacturers in the cut flower industry, as they provide a viable method to substantially extend the vase life of cut flowers. Such an enhancement in flower longevity can lead to increased market value and customer satisfaction. Furthermore, the reduction in flower senescence and decay rates can contribute to decreased waste and greater efficiency in cut flower distribution and sales, offering a substantial advantage to manufacturers in this competitive market. The extended vase life and reduced senescence observed in alstroemeria flowers treated with 1.5mM SA and 3% SU are attributed to SA's role in enhancing endogenous defense responses and sucrose's function as an energy source, collectively improving water uptake, and delaying the natural decay process.

Expression of ethylene biosynthetic genes during flower senescence and in response to ethephon and silver nitrate treatments in Osmanthus fragrans.

Sweet osmanthus (Osmanthus fragrans) is an ornamental evergreen tree species in China, whose flowers are sensitive to ethylene. The synthesis of ethylene is controlled by key enzymes and restriction enzymes, 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), which are encoded by multigene families. However, the key synthase responsible for ethylene regulation in O. fragrans is still unknown. This study aims to screen the key ethylene synthase genes of sweet osmanthus flowers in response to ethylene regulation. In this study, we used the ACO and ACS sequences of Arabidopsis thaliana to search for homologous genes in the O. fragrans petal transcriptome database. These genes were also analyzed bioinformatically. Finally, the expression levels of O. fragrans were compared before and after senescence, as well as after ethephon and silver nitrate treatments. The results showed that there are five ACO genes and one ACS gene in O. fragrans transcriptome database, and the phylogenetic tree revealed that the proteins encoded by these genes had high homology to the ACS and ACO proteins in plants. Sequence alignment shows that the OfACO1-5 proteins have the 2OG-Fe(II) oxygenase domain, while OfACS1 contains seven conserved domains, as well as conserved amino acids in transaminases and glutamate residues related to substrate specificity. Expression analysis revealed that the expression levels of OfACS1 and OfACO1-5 were significantly higher at the early senescence stage compared to the full flowering stage. The transcripts of the OfACS1, OfACO2, and OfACO5 genes were upregulated by treatment with ethephon. However, out of these three genes, only OfACO2 was significantly downregulated by treatment with AgNO3. Our study found that OfACO2 is an important synthase gene in response to ethylene regulation in sweet osmanthus, which would provide valuable data for further investigation into the mechanisms of ethylene-induced senescence in sweet osmanthus flowers.