Understanding quality differences between kiwifruit varieties during softening.

Research into variations between kiwifruit varieties particularly their softening quality during storage is important in improving kiwifruit quality. The potential reasons for ripening quality differences between 'Cuixiang' (CX) and 'Hayward' (HWD) kiwifruit were analyzed by physiology and metabolomic data combined with the random forests learning algorithm. The results showed that the storability difference between the two varieties mainly resulted from differences in polygalacturonase (PG) and ß-galactosidase activities. The 1 °C slowed the fruit softening process of both varieties by decreasing their PG activities. A total of 368 metabolites were identified and amino acid, carbohydrate, cofactors and vitamins, as well as nucleotide metabolism are key metabolic modules that affect the ripening differences of CX and HWD kiwifruit. A total of 30 metabolites showed remarkable ability in distinguish the ripening quality of CX and HWD kiwifruit, in which d-glucose, d-maltose, 2-hydroxybutyric acid, phenyllactate, and vitamin B2 were noteworthy for their potential application on the evaluation of kiwifruit taste and nutritional value. These findings provide positive insights into the underlying mechanism of ripening quality differences between CX and HWD kiwifruit and new ideas for identifying key metabolic markers in kiwifruit.

Physiological and metabolic changes in response to Boron levels are mediated by ethylene affecting tomato fruit yield.

Boron (B) is an essential nutrient for the plant, and its stress (both deficiency and toxicity) are major problems that affect crop production. Ethylene metabolism (both signaling and production) is important to plants' differently responding to nutrient availability. To better understand the connections between B and ethylene, here we investigate the function of ethylene in the responses of tomato (Solanum lycopersicum) plants to B stress (deficiency, 0 µM and toxicity, 640 µM), using ethylene related mutants, namely nonripening (nor), ripening-inhibitor (rin), never ripe (Nr), and epinastic (Epi). Our results show that B stress does not necessarily inhibit plant growth, but both B stress and ethylene signaling severely affected physiological parameters, such as photosynthesis, stomatal conductance, and chlorophyll a fluorescence. Under B toxicity, visible symptoms of toxicity appeared in the roots and margins of the older leaves through necrosis, caused by the accumulation of B which stimulated ethylene biosynthesis in the shoots. Both nor and rin (ethylene signaling) mutants presented similar responses, being these genotypes more sensitive and displaying several morphophysiological alterations, including fruit productivity reductions, in response to the B toxicity conditions. Therefore, our results suggest that physiological and metabolic changes in response to B fluctuations are likely mediated by ethylene signaling.

A translational regulator MHZ9 modulates ethylene signaling in rice.

Ethylene plays essential roles in rice growth, development and stress adaptation. Translational control of ethylene signaling remains unclear in rice. Here, through analysis of an ethylene-response mutant mhz9, we identified a glycine-tyrosine-phenylalanine (GYF) domain protein MHZ9, which positively regulates ethylene signaling at translational level in rice. MHZ9 is localized in RNA processing bodies. The C-terminal domain of MHZ9 interacts with OsEIN2, a central regulator of rice ethylene signaling, and the N-terminal domain directly binds to the OsEBF1/2 mRNAs for translational inhibition, allowing accumulation of transcription factor OsEIL1 to activate the downstream signaling. RNA-IP seq and CLIP-seq analyses reveal that MHZ9 associates with hundreds of RNAs. Ribo-seq analysis indicates that MHZ9 is required for the regulation of ~ 90% of genes translationally affected by ethylene. Our study identifies a translational regulator MHZ9, which mediates translational regulation of genes in response to ethylene, facilitating stress adaptation and trait improvement in rice.

Small Molecules with Thiourea Skeleton Induce Ethylene Response in Arabidopsis.

Ethylene is the only gaseous plant hormone that regulates several aspects of plant growth, from seedling morphogenesis to fruit ripening and organ senescence. Ethylene also stimulates the germination of Striga hermonthica, a root parasitic weed that severely damages crops in sub-Saharan Africa. Thus, ethylene response stimulants can be used as weed and crop control agents. Ethylene and ethephon, an ethylene-releasing compound, are currently used as ethylene response inducers. However, since ethylene is a gas, which limits its practical application, we targeted the development of a solid ethylene response inducer that could overcome this disadvantage. We performed chemical screening using Arabidopsis thaliana "triple response" as an indicator of ethylene response. After screening, we selected a compound with a thiourea skeleton and named it ZKT1. We then synthesized various derivatives of ZKT1 and evaluated their ethylene-like activities in Arabidopsis. Some derivatives showed considerably higher activity than ZKT1, and their activity was comparable to that of 1-aminocyclopropane-1-carboxylate. Mode of action analysis using chemical inhibitors and ethylene signaling mutants revealed that ZKT1 derivatives activate the ethylene signaling pathway through interactions with its upstream components. These thiourea derivatives can potentially be potent crop-controlling chemicals.

Transcriptomic and genetic approaches reveal that the pipecolate biosynthesis pathway simultaneously regulates tomato fruit ripening and quality.

Pipecolic acid (Pip) and N-hydroxypipecolic acid (NHP) have been found to accumulate during the ripening of multiple types of fruits; however, the function and mechanism of pipecolate pathway in fruits remain unclear. Here study was conducted on fruits produced by the model plant tomato, wherein the NHP biosynthesis-related genes, Slald1 and Slfmo1, were mutated. The results showed that the fruits of both the Slald1 and the Slfmo1 mutants exhibited a delayed onset of ripening, decreased fruit size, nutrition and flavor. Exogenous treatment with Pip and NHP promoted fruit ripening and improved fruit quality. Transcriptomic analysis combined with weighted gene co-expression network analysis revealed that the genes involved in the biosynthesis of amino acids, carbon metabolism, photosynthesis, starch and sucrose metabolism, flavonoid biosynthesis, and plant hormone signal transduction were affected by SlFMO1 gene mutation. Transcription factor prediction analysis revealed that the NAC and AP2/ERF-ERF family members are notably involved in the regulation pathway. Overall, our results suggest that the pipecolate biosynthesis pathway is involved in the simultaneous regulation of fruit ripening and quality and indicate that a regulatory mechanism at the transcriptional level exists. However, possible roles of endogenously synthesized Pip and NHP in these processes remain to be determined. The biosynthesis pathway genes SlALD1 and SlFMO1 may be potential breeding targets for promoting fruit ripening and improving fruit quality with concomitant yield increases.

The CALCINEURIN B-LIKE 4/CBL-INTERACTING PROTEIN 3 module degrades repressor JAZ5 during rose petal senescence.

Flower senescence is genetically regulated and developmentally controlled. The phytohormone ethylene induces flower senescence in rose (Rosa hybrida), but the underlying signaling network is not well understood. Given that calcium regulates senescence in animals and plants, we explored the role of calcium in petal senescence. Here, we report that the expression of calcineurin B-like protein 4 (RhCBL4), which encodes a calcium receptor, is induced by senescence and ethylene signaling in rose petals. RhCBL4 interacts with CBL-interacting protein kinase 3 (RhCIPK3), and both positively regulate petal senescence. Furthermore, we determined that RhCIPK3 interacts with the jasmonic acid response repressor jasmonate ZIM-domain 5 (RhJAZ5). RhCIPK3 phosphorylates RhJAZ5 and promotes its degradation in the presence of ethylene. Our results reveal that the RhCBL4-RhCIPK3-RhJAZ5 module mediates ethylene-regulated petal senescence. These findings provide insights into flower senescence, which may facilitate innovations in postharvest technology for extending rose flower longevity.

Entomopathogenic Fungus-Related Priming Defense Mechanisms in Cucurbits Impact Spodoptera littoralis (Boisduval) Fitness.

Entomopathogenic fungi (EPF) exhibit direct and indirect mechanisms to increase plant resistance against biotic and abiotic stresses. Plant responses to these stresses are interconnected by common regulators such as ethylene (ET), which is involved in both iron (Fe) deficiency and induced systemic resistance responses. In this work, the roots of cucurbit seedlings were primed with Metarhizium brunneum (EAMa 01/58-Su strain), and relative expression levels of 18 genes related to ethylene (ET), jasmonic acid (JA), and salicylic acid (SA) synthesis, as well as pathogen-related (PR) protein genes, were studied by reverse transcription-quantitative PCR (qRT-PCR). Effects of priming on Spodoptera littoralis were studied by feeding larvae for 15 days with primed and control plants. Genes showed upregulation in studied species; however, the highest relative expression was observed in roots and shoots of plants with Fe deficiency, demonstrating the complexity and the overlapping degree of the regulatory network. EIN2 and EIN3 should be highlighted; both are key genes of the ET transduction pathway that enhanced their expression levels up to eight and four times, respectively, in shoots of primed cucumber. Also, JA and SA synthesis and PR genes showed significant upregulation during the observation period (e.g., the JA gene LOX1 increased 506 times). Survival and fitness of S. littoralis were affected with significant effects on mortality of larvae fed on primed plants versus controls, length of the larval stage, pupal weight, and the percentage of abnormal pupae. These results highlight the role of the EAMa 01/58-Su strain in the induction of resistance, which could be translated into direct benefits for plant development. IMPORTANCE Entomopathogenic fungi are multipurpose microorganisms with direct and indirect effects on insect pests. Also, EPF provide multiple benefits to plants by solubilizing minerals and facilitating nutrient acquisition. A very interesting and novel effect of these fungi is the enhancement of plant defense systems by inducing systematic and acquired resistance. However, little is known about this function. This study sheds light on the molecular mechanisms involved in cucurbits plants' defense activation after being primed by the EPF M. brunneum. Furthermore, the subsequent effects on the fitness of the lepidopteran pest S. littoralis are shown. In this regard, a significant upregulation was recorded for the genes that regulate JA, SA, and ET pathways. This increased expression of defense genes caused lethal and sublethal effects on S. littoralis. This could be considered an added value for the implementation of EPF in integrated pest management programs.

EcAGL enhances cadmium tolerance in transgenic Arabidopsis thaliana through inhibits cadmium transport and ethylene synthesis pathway.

Cadmium (Cd) is a highly toxic heavy metal with severe impacts on plant growth and development. Although a multitude of plants have acquired strong tolerance to Cd stress, the underlying molecular mechanism has not been fully elucidated. Here, we identified a Agamous-like MADS-box gene (EcAGL) from Erigeron canadensis. The expression of EcAGL was obviously raised under Cd stress and subcellular localization indicated EcAGL was localized in the nucleus. Overexpression of EcAGL in Arabidopsis thaliana showed marked alleviation of the Cd-induced reduction; Compared to wild-type lines, the antioxidant enzymes activities were increased in EcAGL overexpressing lines under Cd stress. The roots Cd content of transgenic lines was not different with the control plants, whereas significant reduction in shoots Cd content was detected in the transgenic lines, indicating that this gene can enhance Cd tolerance by reducing Cd accumulation in Arabidopsis. Moreover, the expression levels of heavy metal ATPase (AtHMA2 and AtHMA3) and natural resistance-associated macrophage protein (AtNRAMP5) genes in the root of transgenic lines decreased under Cd stress, indicating that EcAGL likely hampered the Cd transport pathway. Gene expression profiles in shoot showed that EcAGL likely modulates the expression of 1-aminocyclopropane-1-carboxylic acid synthase gene (AtACS2), which is involved in the ethylene synthesis pathway, to strengthen the tolerance to Cd. Collectively, these results indicate that EcAGL plays a significant role in regulating Cd tolerance in E. canadensis by alleviating oxidative stress, Cd transport and affecting the ethylene biosynthesis pathway, providing new insight into the molecular mechanism underlying plant tolerance to Cd stress.

Banana MKK1 modulates fruit ripening via the MKK1-MPK6-3/11-4-bZIP21 module.

The mitogen-activated protein kinase (MAPK) cascade consisting of MKKK, MKK, and MPK plays an indispensable role in various plant physiological processes. Previously, we showed that phosphorylation of MabZIP21 by MaMPK6-3 is involved in banana fruit ripening, but the regulatory mechanism by which MKK controls banana fruit ripening remains unclear. Here, ripening-induced MaMKK1 from banana fruit is characterized, and transiently overexpressing and silencing of MaMKK1 in banana fruit accelerates and inhibits fruit ripening, respectively, possibly by influencing phosphorylation and activity of MPK. MaMKK1 interacts with and phosphorylates MaMPK6-3 and MaMPK11-4 mainly at the pTEpY residues, resulting in MPK activation. MaMPK11-4 phosphorylates MabZIP21 to elevate its transcriptional activation ability. Transgenic tomato fruit expressing MabZIP21 ripen quickly with a concomitant increase in MabZIP21 phosphorylation. Additionally, MabZIP21 activates MaMPK11-4 and MaMKK1 transcription to form a regulatory feedback loop. Collectively, here we report a regulatory pathway of the MaMPK6-3/11-4-MabZIP21 module in controlling banana fruit ripening.

Auxin-responsive protein MaIAA17-like modulates fruit ripening and ripening disorders induced by cold stress in 'Fenjiao' banana.

Cold stress severely affects the banana fruit softening and de-greening, significantly inhibiting the ripening processes. However, the mechanism of ripening disorder caused by chilling injury (CI) in banana fruit remains largely unknown. Herein, MaIAA17-like, an Auxin/Indole-3-Acetic Acid (Aux/IAA) family member, was found to be highly related to the softening and de-greening in 'Fenjiao' banana. Its expression was rapidly increased with fruit ripening and then gradually decreased under normal ripening conditions (22 °C). Notably, cold storage severely repressed MaIAA17-like expression but was rapidly increased following ethephon treatment for ripening in fruits without CI. However, the expression repression was not reverted in fruits with serious CI symptoms after 12 days of storage at 7 °C. AtMaIAA17-like bound and regulated the activities of promoters of chlorophyll (MaNOL and MaSGR1), starch (MaBAM6 and MaBAM8), and cell wall (MaSUR14 and MaPL8) degradation-related genes. MaIAA17-like also interacted with ethylene-insensitive 3-binding F-box protein (MaEBF1), further activating the expression of MaNOL, MaBAM8, MaPL8, and MaSUR14. Generally, the transient overexpression of MaIAA17-like promoted fruit ripening by inducing the expression of softening and de-greening related genes. However, silencing MaIAA17-like inhibited fruit ripening by reducing the expression of softening and de-greening related genes. These results imply that MaIAA17-like modulates fruit ripening by transcriptionally upregulating the key genes related to fruit softening and de-greening.

The Influence of Lead and Acyrthosiphon pisum (Harris) on Generation of Pisum sativum Defense Signaling Molecules and Expression of Genes Involved in Their Biosynthesis.

The main aim of this study was to understand the regulation of the biosynthesis of phytohormones as signaling molecules in the defense mechanisms of pea seedlings during the application of abiotic and biotic stress factors. It was important to identify this regulation at the molecular level in Pisum sativum L. seedlings under the influence of various concentrations of lead-i.e., a low concentration increasing plant metabolism, causing a hormetic effect, and a high dose causing a sublethal effect-and during feeding of a phytophagous insect with a piercing-sucking mouthpart-i.e., pea aphid (Acyrthosiphon pisum (Harris)). The aim of the study was to determine the expression level of genes encoding enzymes of the biosynthesis of signaling molecules such as phytohormones-i.e., jasmonates (JA/MeJA), ethylene (ET) and abscisic acid (ABA). Real-time qPCR was applied to analyze the expression of genes encoding enzymes involved in the regulation of the biosynthesis of JA/MeJA (lipoxygenase 1 (LOX1), lipoxygenase 2 (LOX2), 12-oxophytodienoate reductase 1 (OPR1) and jasmonic acid-amido synthetase (JAR1)), ET (1-aminocyclopropane-1-carboxylate synthase 3 (ACS3)) and ABA (9-cis-epoxycarotenoid dioxygenase (NCED) and aldehyde oxidase 1 (AO1)). In response to the abovementioned stress factors-i.e., abiotic and biotic stressors acting independently or simultaneously-the expression of the LOX1, LOX2, OPR1, JAR1, ACS3, NCED and AO1 genes at both sublethal and hormetic doses increased. Particularly high levels of the relative expression of the tested genes in pea seedlings growing at sublethal doses of lead and colonized by A. pisum compared to the control were noticeable. A hormetic dose of lead induced high expression levels of the JAR1, OPR1 and ACS3 genes, especially in leaves. Moreover, an increase in the concentration of phytohormones such as jasmonates (JA and MeJA) and aminococyclopropane-1-carboxylic acid (ACC)-ethylene (ET) precursor was observed. The results of this study indicate that the response of pea seedlings to lead and A. pisum aphid infestation differed greatly at both the gene expression and metabolic levels. The intensity of these defense responses depended on the organ, the metal dose and direct contact of the stress factor with the organ.

Genome-Wide Analysis and Identification of 1-Aminocyclopropane-1-Carboxylate Synthase (ACS) Gene Family in Wheat (Triticum aestivum L.).

Ethylene has an important role in regulating plant growth and development as well as responding to adversity stresses. The 1-aminocyclopropane-1-carboxylate synthase (ACS) is the rate-limiting enzyme for ethylene biosynthesis. However, the role of the ACS gene family in wheat has not been examined. In this study, we identified 12 ACS members in wheat. According to their position on the chromosome, we named them TaACS1-TaACS12, which were divided into four subfamilies, and members of the same subfamilies had similar gene structures and protein-conserved motifs. Evolutionary analysis showed that fragment replication was the main reason for the expansion of the TaACS gene family. The spatiotemporal expression specificity showed that most of the members had the highest expression in roots, and all ACS genes contained W box elements that were related to root development, which suggested that the ACS gene family might play an important role in root development. The results of the gene expression profile analysis under stress showed that ACS members could respond to a variety of stresses. Protein interaction prediction showed that there were four types of proteins that could interact with TaACS. We also obtained the targeting relationship between TaACS family members and miRNA. These results provided valuable information for determining the function of the wheat ACS gene, especially under stress.

Physiological responses and Ethylene-Response AP2/ERF Factor expression in Indica rice seedlings subjected to submergence and osmotic stress.

BACKGROUND: The increased frequency of heavy rains in recent years has led to submergence stress in rice paddies, severely affecting rice production. Submergence causes not only hypoxic stress from excess water in the surrounding environment but also osmotic stress in plant cells. We assessed physiological responses and Ethylene-Response AP2/ERF Factor regulation under submergence conditions alone and with ionic or nonionic osmotic stress in submergence-sensitive IR64 and submergence-tolerant IR64-Sub1 Indica rice cultivars. RESULTS: Our results indicate that both IR64 and IR64-Sub1 exhibited shorter plant heights and root lengths under submergence with nonionic osmotic stress than normal condition and submergence alone. IR64-Sub1 seedlings exhibited a significantly lower plant height under submergence conditions alone and with ionic or nonionic osmotic stress than IR64 cultivars. IR64-Sub1 seedlings also presented lower malondialdehyde (MDA) concentration and higher survival rates than did IR64 seedlings after submergence with ionic or nonionic osmotic stress treatment. Sub1A-1 affects reactive oxygen species (ROS) accumulation and antioxidant enzyme activity in rice. The results also show that hypoxia-inducible ethylene response factors (ERF)-VII group and alcohol dehydrogenase 1 (ADH1) and lactate dehydrogenase 1 (LDH1) genes exhibited different expression levels under nonionic or ionic osmotic stress during submergence on rice. CONCLUSIONS: Together, these results demonstrate that complex regulatory mechanisms are involved in responses to the aforementioned forms of stress and offer new insights into the effects of submergence and osmotic stress on rice.

Arabidopsis EIN2 represses ABA responses during germination and early seedling growth by inactivating HLS1 protein independently of the canonical ethylene pathway.

The signaling pathways for the phytohormones ethylene and abscisic acid (ABA) have antagonistic effects on seed germination and early seedling establishment. However, the underlying molecular mechanisms remain unclear. In Arabidopsis thaliana, ETHYLENE INSENSITIVE 2 (EIN2) localizes to the endoplasmic reticulum (ER); although its biochemical function is unknown, it connects the ethylene signal with the key transcription factors EIN3 and EIN3-LIKE 1 (EIL1), leading to the transcriptional activation of ethylene-responsive genes. In this study, we uncovered an EIN3/EIL1-independent role for EIN2 in regulating the ABA response. Epistasis analysis demonstrated that this distinct role of EIN2 in the ABA response depends on HOOKLESS 1 (HLS1), the putative histone acetyltransferase acting as a positive regulator of ABA responses. Protein interaction assays supported a direct physical interaction between EIN2 and HLS1 in vitro and in vivo. Loss of EIN2 function resulted in an alteration of HLS1-mediated histone acetylation at the ABA-INSENSITIVE 3 (ABI3) and ABI5 loci, which promotes gene expression and the ABA response during seed germination and early seedling growth, indicating that the EIN2-HLS1 module contributes to ABA responses. Our study thus revealed that EIN2 modulates ABA responses by repressing HLS1 function, independently of the canonical ethylene pathway. These findings shed light on the intricate regulatory mechanisms underling the antagonistic interactions between ethylene and ABA signaling, with significant implications for our understanding of plant growth and development.

Gamma irradiation delays tomato (Solanum lycopersicum) ripening by inducing transcriptional changes.

BACKGROUND: Tomato (Solanum lycopersicum) has a relatively short shelf life as a result of rapid ripening, limiting its transportability and marketability. Recently, gamma irradiation has emerged as a viable method for delaying tomato fruit ripening. Although few studies have shown that gamma irradiation delays the ripening of tomatoes, the underlying mechanism remains unknown. Therefore, the present study aimed to examine the effects of gamma irradiation on tomato fruit ripening and the underlying mechanisms using transcriptomics. RESULTS: Following gamma irradiation, the total microbial count, weight loss, and decay rate of tomatoes significantly reduced during storage. Furthermore, the redness (a*), color change (∆E), and lycopene content of gamma-irradiated tomatoes decreased in a dose-dependent manner during storage. Moreover, gamma irradiation significantly upregulated the expression levels of genes associated with DNA, chloroplast, and oxidative damage repairs, whereas those of ethylene and auxin signaling-, ripening-, and cell wall metabolism-related, as well as carotenoid genes, were downregulated. CONCLUSION: Gamma irradiation effectively delayed ripening by downregulating the expression of ripening-related genes and inhibiting microbial growth, which prevented decay and prolonged the shelf life of tomatoes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ethephon promotes isoflavone accumulation in germinating soybeans by its acceleration of isoflavone biosynthetic pathway.

Soybeans have medicinal value and are an oil crop with medicinal and food properties. The present work investigated two aspects of isoflavone accumulation in soybean. First, germination conditions for exogenous-ethephon-mediated accumulation of isoflavone were optimised through response surface methodology. Second, various influences of ethephon on the growth of germinating soybeans and isoflavone metabolism were investigated. The findings of the research led to the conclusion that exogenous ethephon treatment effectively facilitated the enrichment of isoflavones in soybeans during germination. Optimal germination conditions were obtained through a response surface optimization test, which yielded the following criteria: a germination time of 4.2 d, an ethephon concentration of 102.6 µM, and a germination temperature of 30.2 °C. The maximum isoflavone content was 544.53 µg/sprout FW. Relative to the control, the addition of ethephon significantly inhibited sprout growth. Exogenous ethephon treatment led to the phenomenon that peroxidase, superoxide dismutase, and catalase activities and their gene expression increased significantly in germinating soybeans. Meanwhile, the expression of genes related to ethylene synthetase increase under the effect of ethephon promoting ethylene synthesis. Ethylene multiplied the total flavonoid content of soybean sprouts relying on the increase in activity and gene expression of crucial isoflavone biosynthesis-related enzymes (phenylalanine ammonia-lyase and 4-coumarate coenzyme A ligase) during germination.

The local and systemic accumulation of ethylene determines the rapid defence responses induced by flg22 in tomato (Solanum lycopersicum L.).

Plant defence responses induced by the bacterial elicitor flg22 are highly dependent on phytohormones, including gaseous ethylene (ET). While the regulatory role of ET in local defence responses to flg22 exposure has been demonstrated, its contribution to the induction of systemic responses is not clearly understood. For this consideration, we examined the effects of different ET modulators on the flg22-induced local and systemic defence progression. In our experiments, ET biosynthesis inhibitor aminoethoxyvinyl glycine (AVG) or ET receptor blocker silver thiosulphate (STS) were applied 1 h before flg22 treatments and 1 h later the rapid local and systemic responses were detected in the leaves of intact tomato plants (Solanum lycopersicum L.). Based on our results, AVG not only diminished the flg22-induced ET accumulation locally, but also in the younger leaves confirming the role of ET in the whole-plant expanding defence progression. This increase in ET emission was accompanied by increased local expression of SlACO1, which was reduced by AVG and STS. Local ET biosynthesis upon flg22 treatment was shown to positively regulate local and systemic superoxide (O2.-) and hydrogen peroxide (H2O2) production, which in turn could contribute to ET accumulation in younger leaves. Confirming the role of ET in flg22-induced rapid defence responses, application of AVG reduced local and systemic ET, O2.- and H2O2 production, whereas STS reduced it primarily in the younger leaves. Interestingly, in addition to flg22, AVG and STS induced stomatal closure alone at whole-plant level, however in the case of combined treatments together with flg22 both ET modulators reduced the rate of stomatal closure in the older- and younger leaves as well. These results demonstrate that both local and systemic ET production in sufficient amounts and active ET signalling are essential for the development of flg22-induced rapid local and systemic defence responses.

The swansong of petal cell death: insights into the mechanism and regulation of ethylene-mediated flower senescence.

Flower senescence is a fundamental aspect of the developmental trajectory in flowers, occurring after the differentiation of tissues and maturation of petals, and preceding the growth and development of seeds. It is accompanied by various alterations at the cytological, physiological, and molecular levels, similar to other forms of programmed cell death (PCD). It involves an intricate interplay of various plant growth regulators, with ethylene being the key orchestrator in ethylene-dependent petal senescence. Petal senescence mediated by ethylene is marked by various changes such as petal wilting, amplified oxidative stress, degradation of proteins and nucleic acids, and autophagy. Ethylene crosstalks with other growth regulators and triggers genetic and/or epigenetic reprogramming of genes during senescence in flowers. While our understanding of the mechanism and regulation of petal senescence in ethylene-sensitive species has advanced, significant knowledge gaps still exist, which demand critical reappraisal of the available literature on the topic. A deeper understanding of the various mechanisms and regulatory pathways involved in ethylene-dependent senescence has the capacity to facilitate a more precise regulation of the timing and site of senescence, thus leading to optimized crop yields, enhanced product quality, and extended longevity.

How far can omics go in unveiling the mechanisms of floral senescence?

Floral senescence is of fundamental interest in understanding plant developmental regulation, it is of ecological and agricultural interest in relation to seed production, and is of key importance to the production of cut flowers. The biochemical changes occurring are well-studied and involve macromolecular breakdown and remobilisation of nutrients to developing seeds or other young organs in the plant. However, the initiation and regulation of the process and inter-organ communication remain to be fully elucidated. Although ethylene emission, which becomes autocatalytic, is a key regulator in some species, in other species it appears not to be as important. Other plant growth regulators such as cytokinins, however, seem to be important in floral senescence across both ethylene sensitive and insensitive species. Other plant growth regulators are also likely involved. Omics approaches have provided a wealth of data especially in ornamental species where genome data is lacking. Two families of transcription factors: NAC and WRKY emerge as major regulators, and omics information has been critical in understanding their functions. Future progress would greatly benefit from a single model species for understanding floral senescence; however, this is challenging due to the diversity of regulatory mechanisms. Combining omics data sets can be powerful in understanding different layers of regulation, but in vitro biochemical and or genetic analysis through transgenics or mutants is still needed to fully verify mechanisms and interactions between regulators.

Exogenous gibberellin delays maturation in persimmon fruit through transcriptional activators and repressors.

As the harvest season of most fruit is concentrated, fruit maturation manipulation is essential for the fresh fruit industry to prolong sales time. Gibberellin (GA), an important phytohormone necessary for plant growth and development, has also shown a substantial regulatory effect on fruit maturation; however, its regulatory mechanisms remain inconclusive. In this research, preharvest GA3 treatment effectively delayed fruit maturation in several persimmon (Diospyros kaki) cultivars. Among the proteins encoded by differentially expressed genes, 2 transcriptional activators (NAC TRANSCRIPTION FACTOR DkNAC24 and ETHYLENE RESPONSIVE FACTOR DkERF38) and a repressor (MYB-LIKE TRANSCRIPTION FACTOR DkMYB22) were direct regulators of GERANYLGERANYL DIPHOSPHATE SYNTHASE DkGGPS1, LYSINE HISTIDINE TRANSPORTER DkLHT1, and FRUCTOSE-BISPHOSPHATE ALDOLASE DkFBA1, respectively, resulting in the inhibition of carotenoid synthesis, outward transport of an ethylene precursor, and consumption of fructose and glucose. Thus, the present study not only provides a practical method to prolong the persimmon fruit maturation period in various cultivars but also provides insights into the regulatory mechanisms of GA on multiple aspects of fruit quality formation at the transcriptional regulation level.