Expression Of Ethylene-related Genes Research Articles

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

Cavendish bananas are climacteric fruits that rapidly respond to biochemical reactions during ripening. Therefore, it quickly undergoes a decrease in commercial value during post-harvest storage. This study evaluated the effect of Fruit Storage Chamber (FSC) modification on the photoactivation of nanoparticles blue-TiO2-x and 1.25 % (w/v) chitosan coatings on the physicochemical and molecular characteristics of Cavendish bananas stored at a low temperature (22 °C). The results showed that the combination of FSC treatment supplemented with nanoparticles blue-TiO2-x and bananas coated with 1.25 % (w/v) chitosan can maintain fruit quality during seven days of storage at 22 °C, compared to the control. Applying both of nanoparticles blue-TiO2-x variants with chitosan-coated bananas can suppress the relative expression of the MaACS1 gene until the 5th day but lead to an up-regulated expression on the following day. However, the control sample stored in FSC with nanoparticles blue-TiO2-x was the best treatment to suppress relative MaACS1 (Musa acuminata ACC synthase 1) and MaACO1 (Musa acuminata ACC Oxidase 1) gene expression in the pulp until the end of shelf life. It means the treated sample with 1.25 % chitosan could suppress MaACO1 gene expression six times more than a banana without chitosan while in storage without FSC. MaACO1 expression in nanoparticles blue-TiO2-x bananas coated with 1.25 % (w/v) chitosan decreased 28-fold during storage 7 days. This study suggested that a 1.25 % chitosan coating combined with storage in FSC with nanoparticles blue-TiO2-x can inhibit ACC oxidase from converting ACC to ethylene. This study demonstrated that an FSC equipped with nano-TiO2 variants, low temperature, and 1.25 % (w/v) chitosan coating is a promising solution that could delay ripening and extend the shelf life of Cavendish bananas.

Nano-TiO2 enhanced fruit storage chambers: unveiling the potential for prolonging banana shelf life

ABSTRACT This manuscript focuses on the development of Fruit Storage Chamber (FSC) equipped with nano-TiO2 and its modular prototype to improve the value of bamboo-based FSC by its photocatalytic and feasibility aspects. Its effects on fruit shelf life and ripening-related gene expression were studied. Cavendish bananas were stored in FSC equipped with nano-TiO2 and modular FSC for treatments. Relative expression level of ethylene biosynthesis-related (MaACS1, MaACO1) and polyphenol oxidase (MaPPO4, MaPPO5) genes were examined. The dynamics of ripening variables throughout the storage period were illustrated in regression lines, followed with hypothesis testing. Banana quantity showed no significant changes upon storage in FSC equipped with nano-TiO2. Physical appearance indicated a ripening delay of up to two days on nano-TiO2 treatments compared to control. Ethylene production rate and ethylene related gene expression were not significantly altered. Browning index was more maintained in nano-TiO2 treated samples, supported by the observation of slower increase of MaPPO4 and MaPPO5 relative expressions compared to control. The findings highlight the suppression of fruit ripening related gene expression and the maintenance of fruit quality in treated samples compared to control, indicating the potential use of nano-TiO2 to prolong banana shelf life.

Silver nitrate reduces hyperhydricity in shoots regenerated from the hypocotyl of snapdragon cv. Maryland Apple Blossom

We developed an efficient protocol for shoot regeneration from hypocotyl explants in snapdragon (Antirrhinum majus L.) cv. Maryand Apple Blossom by plant growth regulators (PGRs), followed by ethylene synthesis inhibitor Aminoethoxyvinylglycine (AVG), ethylene precursor 1-Aminocyclopropane-1-carboxylate (ACC), and ethylene action inhibitor silver nitrate (AgNO3). The combination of benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D) did not induce shoots, whereas naphthaleneacetic acid (NAA) and Zeatin (Zt) induced shoots. The combination of 0.05 mg/L NAA and 2.5 mg/L Zt resulted in the maximum shoot regeneration percentage and a reasonable number of shoots per explant. However, the regenerated shoots exhibited hyperhydricity and failed to develop into normal plants when introduced into plant growth media. Addition of ACC and AVG to the media containing 0.05 mg/L NAA and 2.5 mg/L Zt inhibited shoot regeneration, while AgNO3 (2.0 mg/L) marginally improved shoot regeneration and successfully reduced hyperhydricity. Shoots grown in AgNO3-containing media showed a reduction in ethylene related gene expression and reactive oxygen species (ROS) accumulation; the leaves showed reduced intercellular space as well as an increase in the number of open stomata under AgNO3 treatment. Moreover, shoots regenerated from AgNO3-containing media easily developed into normal plants in plant growth medium. This study highlights the importance of specific PGRs in shoot regeneration, as well as the role of AgNO3 in reducing the hyperhydricity of shoots regenerated in vitro. These findings will contribute to a better understanding of the hyperhydricity mechanism. We expect this protocol to be useful for in vitro shoot regeneration and genetic transformation of the snapdragon cultivar used in this study.

High light stress induces H2O2 production and accelerates fruit ripening in tomato

Increased synthesis of H2O2 is observed during the initiation of fruit ripening. However, its association with plant cell processes triggering the maturation of fruit has not yet been demonstrated. The aim of this work is to investigate whether H2O2 participates in the tomato ripening process and particularly through its association with the ethylene signaling pathway. The experiments were carried out with two ethyl methanesulfonate mutant lines of Micro-Tom tomato deficient in GDP-L-galactose phosphorylase activity and displaying lower ascorbic acid content than the corresponding parental genotype (i.e. wild type). Plants were subjected to a high irradiance (HI) treatment to stimulate H2O2 synthesis. HI treatment enhanced H2O2 production and reduced the timing of fruit ripening in both mutants and wild-type fruits. These results could be linked to an increase of the expression of H2O2-related genes and changes in the expression of ethylene-related genes. The fruit H2O2 production increased or decreased after applying the treatments that induced ethylene synthesis or blocked its action, respectively. The results presented in this work give an evidence of the association of redox and hormonal components during fruit ripening in which H2O2 participates downstream in the events regulated by ethylene.

Deciphering Precise Gene Transcriptional Expression Using gwINTACT in Tomato.

Functional gene transcription mainly occurs in the nucleus and has a significant role in plant physiology. The isolation of nuclei tagged in specific cell type (INTACT) technique provides an efficient and stable nucleus purification method to investigate the dynamic changes of nuclear gene transcriptional expression. However, the application of traditional INTACT in plants is still limited to seedlings or root cells because of severe chloroplast pollution. In this study, we proposed a newly designed and simplified INTACT based on mas-enhanced GFP (eGFP)-SlWIP2 (gwINTACT) for nuclear purification in tomato (Solanum lycopersicum) leaves, flowers, and fruits for the first time. The yield of the nucleus purified using gwINTACT from transgenic tomato leaves was doubled compared with using a traditional INTACT procedure, accompanied by more than 95% removal of chloroplasts. Relative gene expression of ethylene-related genes with ethylene treatment was reevaluated in gwINTACT leaves to reveal more different results from the traditional gene expression assay based on total RNA. Therefore, establishing the gwINTACT system in this study facilitates the precise deciphering of the transcriptional status in various tomato tissues, which lays the foundation for the further experimental study of nucleus-related molecular regulation on fruit ripening, such as ChIP-seq and ATAC-seq.

Bacterial Modulation of the Plant Ethylene Signaling Pathway Improves Tolerance to Salt Stress in Lettuce (Lactuca sativa L.)

Salinity has extensive adverse effects on plant growth and the development of new agronomic strategies to improve crop salt tolerance is becoming necessary. Currently, the use of plant growth promoting rhizobacteria (PGPR) to mitigate abiotic stress in crops is of increasing interest. The most analyzed mechanism is based on ACC deaminase activity, an enzyme that decreases the ethylene synthesis, an important phytohormone in plant stress response. We aimed to identify other PGPR mediated mechanisms involved in the regulation of salt stress in plant. We used three PGPR strains (ESL001, ESL007, SH31), of which only ESL007 demonstrated ACC deaminase activity, to evaluate their effect on lettuce plants under salt stress (100 mM NaCl). We measured growth and biochemical parameters (e.g., proline content, lipid peroxidation and ROS degradation), as well as expression levels of genes involved in ethylene signaling (CTR1, EBF1) and transcription factors induced by ethylene (ERF5, ERF13). All bacterial strains enhanced growth on salt-stressed lettuce plants and modulated the proline levels. Strains ESL007 and SH31 triggered a higher catalase and ascorbate-peroxidase activity, compared to non-stressed plants. Differential expression of ethylene-related genes in inoculated plants subjected to salinity was observed. We gained consistent evidence for the existence of alternative mechanisms to ethylene modulation, which probably rely on bacterial IAA production and other chemical signals. These mechanisms modify the expression of genes associated with ethylene signaling and regulation, complementarily to the ACC deaminase model to diminish abiotic stress responses.

Effect of 1-MCP and ethylene absorbent on the development of lenticel disorder of 'Xinli No.7' pear and possible mechanisms.

A common lenticel disorder which occurs in the peel of 'Xinli No. 7' pears (Pyrus bretschneideri Rehd.) had not previously been described. Symptoms of this lenticel disorder include enlarging and bulging of the lenticels which results in significant commercial losses. Understanding the physiological basis of lenticel disorder and developing practical methods to control it is crucial for the successful marketing of this pear. The development of this lenticel disorder was found to be closely related to the endogenous ethylene production during storage. 1-Methylcyclopropene (1-MCP) combined with an ethylene absorbent (EA) treatment was found to significantly reduce the development of the disorder by inhibiting the expression of ethylene related genes, PbACS1, PbACS2 and PbACO. It is proposed that the enlarged lenticels may result from increased lignin accumulation in the peel cells, which is inhibited by this combined postharvest treatment. It was shown that the expression of six lignin related genes decreased following the treatment. The results suggest that PbPAL, Pb4CL and PbCAD could be critical in regulating the development of this lenticel disorder. Endogenous ethylene plays a key role in the development of this lenticel disorder in 'Xinli No. 7' pear. The enlarged lenticels which is characteristic of this disorder maybe related to increased lignin accumulation in the peel cells, which were inhibited with 1-MCP combined with an EA treatment. These results provide a practical method for managing the development of lenticel disorder in 'Xinli No. 7' pear and helps clarify the developmental mechanisms of this disorder. © 2020 Society of Chemical Industry.

Melatonin: A master regulator of plant development and stress responses.

Melatonin is a pleiotropic molecule with multiple functions in plants. Since the discovery of melatonin in plants, numerous studies have provided insight into the biosynthesis, catabolism, and physiological and biochemical functions of this important molecule. Here, we describe the biosynthesis of melatonin from tryptophan, as well as its various degradation pathways in plants. The identification of a putative melatonin receptor in plants has led to the hypothesis that melatonin is a hormone involved in regulating plant growth, aerial organ development, root morphology, and the floral transition. The universal antioxidant activity of melatonin and its role in preserving chlorophyll might explain its anti-senescence capacity in aging leaves. An impressive amount of research has focused on the role of melatonin in modulating postharvest fruit ripening by regulating the expression of ethylene-related genes. Recent evidence also indicated that melatonin functions in the plant's response to biotic stress, cooperating with other phytohormones and well-known molecules such as reactive oxygen species and nitric oxide. Finally, great progress has been made towards understanding how melatonin alleviates the effects of various abiotic stresses, including salt, drought, extreme temperature, and heavy metal stress. Given its diverse roles, we propose that melatonin is a master regulator in plants.

Differential Expression of Ethylene Signaling and Biosynthesis Genes in Floral Organs Between Ethylene-Sensitive and -Insensitive Rose Cultivars

The plant hormone ethylene regulates diverse aspects of plant growth and development, including flower senescence and abscission. In cut roses, the impact of ethylene on flower senescence varies greatly depending on the ethylene sensitivity of the floral organs, which is determined by the variety of the rose. To understand the relationship between ethylene synthesis and sensitivity in floral organs, we examined tissue-specific differences in gene expression and regulation using two rose cultivars with differing ethylene sensitivity. We monitored the expression patterns of genes related to ethylene biosynthesis (RhACS1, RhACS2, RhACS3, RhACS4, and RhACO1), receptor (RhETR1, RhETR2, RhETR3, RhETR4, and RhETR5), and signaling (RhCTR1, RhCTR2, RhEIN3-1, RhEIN3-2, and RhEIN3-3) in various floral organs of ethylene-sensitive (SENS; ‘All For Love’) and -insensitive (INSENS; ‘Peach Valley’) rose cultivars. The expression of ethylene-related genes in all floral organs was generally higher in SENS than INSENS cultivars. The presence of exogenous ethylene accelerated the accumulation of RhACS1-4 and RhACO1 transcripts in SENS petals and leaves and in INSENS stamens and stigmas, leading to an increase in RhETR1-5 expression in the floral organs. Meanwhile, RhCTR1-2 expression decreased considerably, with a consequent increase in RhEIN3 transcripts in SENS petals and leaves and INSENS stamens and stigmas. The differential expression of ethylene- related genes in the same tissues indicates that the site of initiation of the ethylene-inducible responses varies among the varieties, and this is probably related to the ethylene sensitivity of the flowers.

Ethylene-Related Gene Expression Networks in Wood Formation.

Thickening of tree stems is the result of secondary growth, accomplished by the meristematic activity of the vascular cambium. Secondary growth of the stem entails developmental cascades resulting in the formation of secondary phloem outwards and secondary xylem (i.e., wood) inwards of the stem. Signaling and transcriptional reprogramming by the phytohormone ethylene modifies cambial growth and cell differentiation, but the molecular link between ethylene and secondary growth remains unknown. We addressed this shortcoming by analyzing expression profiles and co-expression networks of ethylene pathway genes using the AspWood transcriptome database which covers all stages of secondary growth in aspen (Populus tremula) stems. ACC synthase expression suggests that the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) is synthesized during xylem expansion and xylem cell maturation. Ethylene-mediated transcriptional reprogramming occurs during all stages of secondary growth, as deduced from AspWood expression profiles of ethylene-responsive genes. A network centrality analysis of the AspWood dataset identified EIN3D and 11 ERFs as hubs. No overlap was found between the co-expressed genes of the EIN3 and ERF hubs, suggesting target diversification and hence independent roles for these transcription factor families during normal wood formation. The EIN3D hub was part of a large co-expression gene module, which contained 16 transcription factors, among them several new candidates that have not been earlier connected to wood formation and a VND-INTERACTING 2 (VNI2) homolog. We experimentally demonstrated Populus EIN3D function in ethylene signaling in Arabidopsis thaliana. The ERF hubs ERF118 and ERF119 were connected on the basis of their expression pattern and gene co-expression module composition to xylem cell expansion and secondary cell wall formation, respectively. We hereby establish data resources for ethylene-responsive genes and potential targets for EIN3D and ERF transcription factors in Populus stem tissues, which can help to understand the range of ethylene targeted biological processes during secondary growth.

Molecular Insights into the Involvement of a Never Ripe Receptor in the Interaction Between Two Beneficial Soil Bacteria and Tomato Plants Under Well-Watered and Drought Conditions.

Management of plant growth-promoting bacteria (PGPB) can be implemented to deal with sustainable intensification of agriculture. Ethylene is an essential component for plant growth and development and in response to drought. However, little is known about the effects of bacterial inoculation on ethylene transduction pathway. Thus, the present study sought to establish whether ethylene perception is critical for growth induction by two different PGPB strains under drought conditions and the analysis of bacterial effects on ethylene production and gene expression in tomatoes (Solanum lycopersicum). The ethylene-insensitive never ripe (nr) and its isogenic wild-type (wt) cv. Pearson line were inoculated with either Bacillus megaterium or Enterobacter sp. strain C7 and grown until the attainment of maturity under both well-watered and drought conditions. Ethylene perception is crucial for B. megaterium. However, it is not of prime importance for Enterobacter sp. strain C7 PGPB activity under drought conditions. Both PGPB decreased the expression of ethylene-related genes in wt plants, resulting in stress alleviation, while only B. megaterium induced their expression in nr plants. Furthermore, PGPB inoculation affected transcriptomic profile dependency on strain, genotype, and drought. Ethylene sensitivity determines plant interaction with PGPB strains. Enterobacter sp. strain C7 could modulate amino-acid metabolism, while nr mutation causes a partially functional interaction with B. megaterium, resulting in higher oxidative stress and loss of PGPB activity.

Quality and expression of ethylene response genes of ‘Daebong’ persimmon fruit during ripening at different temperatures

This study was conducted to investigate the changes in quality and ethylene related genes expression in astringent persimmon ‘Daebong' during ripening at 15°C and 25°C after an application of 100μgkg−1 ethylene. Ethylene production in treated fruit was higher than in untreated fruit throughout the ripening period. Total soluble solids content was reduced slightly during ripening in both treatment and control fruit. However, the reducing sugar content was increased as ripening proceeded. Firmness and water soluble tannin contents were reduced with similar patterns in treated fruit during ripening at both temperatures. Ethylene treated fruit showed more rapid expression of DKEIL, DKERF2, DKERF5 and DKERF8 genes at 25°C than 15°C. In conclusion, ethylene treatment improved the ripening quality of astringent persimmon regardless of temperature. In addition, the expression of ethylene related genes was higher at 25°C than 15°C, which may be associated with faster ripening.

Regulation of ethylene-related gene expression by indole-3-acetic acid and 4-chloroindole-3-acetic acid in relation to pea fruit and seed development.

In pea, the auxins 4-chloroindole-3-acetic acid (4-Cl-IAA) and indole-3-acetic acid (IAA) occur naturally; however, only 4-Cl-IAA stimulates pericarp growth and gibberellin (GA) biosynthesis, and inhibits the ethylene response in deseeded ovaries (pericarps), mimicking the presence of seeds. Expression of ovary ethylene biosynthesis genes was regulated similarly in most cases by the presence of 4-Cl-IAA or seeds. PsACS1 [which encodes an enzyme that synthesizes 1-aminocyclopropane-1-carboxylic acid (ACC)] transcript abundance was high in pericarp tissue adjacent to developing seeds following pollination. ACC accumulation in 4-Cl-IAA-treated deseeded pericarps was driven by high PsASC1 expression (1800-fold). 4-Cl-IAA, but not IAA, also suppressed the pericarp transcript levels of PsACS4. 4-Cl-IAA increased PsACO1 and decreased PsACO2 and PsACO3 expression (enzymes that convert ACC to ethylene) but did not change ACO enzyme activity. Increased ethylene was countered by a 4-Cl-IAA-specific decrease in ethylene responsiveness potentially via modulation of pericarp ethylene receptor and signaling gene expression. This pattern did not occur in IAA-treated pericarps. Overall, the effect of 4-Cl-IAA and IAA on ethylene biosynthesis gene expression generally explains the ethylene evolution patterns, and their effects on GA biosynthesis and ethylene signaling gene expression explain the tissue response patterns in young pea ovaries.

Suppression of the MADS-box gene SlMBP8 accelerates fruit ripening of tomato (Solanum lycopersicum)

MADS-box genes encode important transcription factors that are involved in many biological processes of plants, including fruit ripening. In our research, a MADS-box gene, SlMBP8, was identified, and its tissue-specific expression profiles were analysed. SlMBP8 was highly expressed in fruits of the B+4 stage, in senescent leaves and in sepals. To further characterize its function, an RNA interference (RNAi) expression vector of SlMBP8 was constructed and transferred into tomato. In the transgenic plants, the ripening of fruits was shortened by 2–4 days compared to that of wild type. At the same time, carotenoids accumulated to higher levels and the expression of phytone synthase 1 (PSY1), phytoene desaturase (PDS) and ς-carotene desaturase (ZDS) was enhanced in RNAi fruits. The transgenic fruits and seedlings showed more ethylene production compared with that of the wild type. Furthermore, SlMBP8-silenced seedlings displayed shorter hypocotyls due to higher endogenous ethylene levels, suggesting that SlMBP8 may modulates the ethylene triple response negatively. A yeast two-hybrid assay indicated that SlMBP8 could interact with SlMADS-RIN. Besides, the expression of ethylene-related genes, including ACO1, ACO3, ACS2, ERF1, E4 and E8, was simultaneously up-regulated in transgenic plants. In addition, SlMBP8-silenced fruits showed higher ethylene production, suggesting that suppressed expression of SlMBP8 promotes carotenoid and ethylene biosynthesis. In addition, the fruits of transgenic plants displayed more rapid water loss and decreased storability compared to wild type, which was due to the significantly induced expressions of cell wall metabolism genes such as PG, EXP, HEX, TBG4, XTH5 and XYL. These results suggest that SlMBP8 plays an important role in fruit ripening and softening.

Sound waves delay tomato fruit ripening by negatively regulating ethylene biosynthesis and signaling genes

Regulation of tomato fruit ripening may help extend fruit shelf life and prevent losses due to spoilage. Here, tomato fruit were investigated whether sound treatment could delay their ripening. Harvested fruit were treated with low-frequency sound waves (1kHz) for 6h, and then monitored various characteristics of the fruit over 14-days at 23±1°C. Seven days after the treatment, 85% of the treated fruit were green, versus fewer than 50% of the non-treated fruit. Most of the tomato fruit had transitioned to the red ripening stage by 14 days after treatment. Ethylene production and respiration rate were lower in the sound-treated than non-treated tomatoes. Furthermore, changes in surface color and flesh firmness were delayed in the treated fruit. To investigate how sound wave treatment effects on fruit ripening, the expression of ethylene-related genes was analyzed by quantitative real-time RT-PCR analysis. The expression level of several ethylene biosynthetic (ACS2, ACS4, ACO1, E4 and E8) and ripening-regulated (RIN, TAGL1, HB-1, NOR, CNR) genes was influenced by sound wave treatment. These results indicated that sound wave treatment delays tomato fruit ripening by altering the expression of important genes in the ethylene biosynthesis and ethylene signaling pathways.

Dissection of jasmonate functions in tomato stamen development by transcriptome and metabolome analyses.

BackgroundJasmonates are well known plant signaling components required for stress responses and development. A prominent feature of jasmonate biosynthesis or signaling mutants is the loss of fertility. In contrast to the male sterile phenotype of Arabidopsis mutants, the tomato mutant jai1-1 exhibits female sterility with additional severe effects on stamen and pollen development. Its senescence phenotype suggests a function of jasmonates in regulation of processes known to be mediated by ethylene. To test the hypothesis that ethylene involved in tomato stamen development is regulated by jasmonates, a temporal profiling of hormone content, transcriptome and metabolome of tomato stamens was performed using wild type and jai1-1.ResultsWild type stamens showed a transient increase of jasmonates that is absent in jai1-1. Comparative transcriptome analyses revealed a diminished expression of genes involved in pollen nutrition at early developmental stages of jai1-1 stamens, but an enhanced expression of ethylene-related genes at late developmental stages. This finding coincides with an early increase of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in jai1-1 and a premature pollen release from stamens, a phenotype similarly visible in an ethylene overproducing mutant. Application of jasmonates to flowers of transgenic plants affected in jasmonate biosynthesis diminished expression of ethylene-related genes, whereas the double mutant jai1-1 NeverRipe (ethylene insensitive) showed a complementation of jai1-1 phenotype in terms of dehiscence and pollen release.ConclusionsOur data suggest an essential role of jasmonates in the temporal inhibition of ethylene production to prevent premature desiccation of stamens and to ensure proper timing in flower development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0135-3) contains supplementary material, which is available to authorized users.

Effect of ethylene treatment on phytochemical and ethylene-related gene expression during ripening in strawberry fruit Fragaria x ananassa cv. Camino Real.

In contrast to climacteric fruits, in which ethylene is known to be pivotal, the regulation of ripening in non-climacteric fruits is not well understood. The strawberry is a typical example of a non-climacteric fruit, which has been used as a model system of these types of fruit. In this study, the effect of exogenous ethephon on the expression of ethylene biosynthesis and signaling genes, FaERF2 and FaACO1, was analyzed in the Fragaria ananassa cultivar Camino Real by quantitative real-time polymerase chain reaction, and the physicochemical and phytochemical characteristics of fruits were evaluated in field trials and postharvest tests. Transcript accumulation was influenced by exogenous treatment with ethephon, which affected the pattern of gene expression during different stages of growth and fruit development, with the highest expression occurring during postharvest tests. In addition, ethephon significantly influenced the phytochemical profile of sugars, anthocyanins, phenolic compounds, and vitamin C contents both in the field- and postharvest-treated fruits at different stages. These results indicate that ethylene regulates the phenylpropanoid maturation pathway in strawberry fruit.

The relationship between the expression of ethylene-related genes and papaya fruit ripening disorder caused by chilling injury.

Papaya (Carica papaya L.) is sensitive to low temperature and easy to be subjected to chilling injury, which causes fruit ripening disorder. This study aimed to investigate the relationship between the expression of genes related to ethylene and fruit ripening disorder caused by chilling injury. Papaya fruits were firstly stored at 7°C and 12°C for 25 and 30 days, respectively, then treated with exogenous ethylene and followed by ripening at 25°C for 5 days. Chilling injury symptoms such as pulp water soaking were observed in fruit stored at 7°C on 20 days, whereas the coloration and softening were completely blocked after 25 days, Large differences in the changes in the expression levels of twenty two genes involved in ethylene were seen during 7°C-storage with chilling injury. Those genes with altered expression could be divided into three groups: the group of genes that were up-regulated, including ACS1/2/3, EIN2, EIN3s/EIL1, CTR1/2/3, and ERF1/3/4; the group of genes that were down-regulated, including ACO3, ETR1, CTR4, EBF2, and ERF2; and the group of genes that were un-regulated, including ACO1/2, ERS, and EBF1. The results also showed that pulp firmness had a significantly positive correlation with the expression of ACS2, ACO1, CTR1/4, EIN3a/b, and EBF1/2 in fruit without chilling injury. This positive correlation was changed to negative one in fruit after storage at 7°C for 25 days with chilling injury. The coloring index displayed significantly negative correlations with the expression levels of ACS2, ACO1/2, CTR4, EIN3a/b, ERF3 in fruit without chilling injury, but these correlations were changed into the positive ones in fruit after storage at 7°C for 25 days with chilling injury. All together, these results indicate that these genes may play important roles in the abnormal softening and coloration with chilling injury in papaya.

Differential behavior within a grapevine cluster: decreased ethylene-related gene expression dependent on auxin transport is correlated with low abscission of first developed berries.

In grapevine, fruit abscission is known to occur within the first two to three weeks after flowering, but the reason why some berries in a cluster persist and others abscise is not yet understood. Ethylene sensitivity modulates abscission in several fruit species, based on a mechanism where continuous polar auxin transport across the pedicel results in a decrease in ethylene perception, which prevents abscission. In grapevine, flowering takes about four to seven days in a single cluster, thus while some flowers are developing into berries, others are just starting to open. So, in this work it was assessed whether uneven flowering accounted for differences in berry abscission dependent on polar auxin transport and ethylene-related gene expression. For this, flowers that opened in a cluster were tagged daily, which allowed to separately analyze berries, regarding their ability to persist. It was found that berries derived from flowers that opened the day that flowering started – named as “first berries” – had lower abscission rate than berries derived from flowers that opened during the following days – named as “late berries”. Use of radiolabeled auxin showed that “first berries” had higher polar auxin transport, correlated with lower ethylene content and lower ethylene-related transcript abundance than “late berries”. When “first berries” were treated with a polar auxin transport inhibitor they showed higher ethylene-related transcript abundance and were more prone to abscise than control berries. This study provides new insights on fruit abscission control. Our results indicate that polar auxin transport sustains the ability of “first berries” to persist in the cluster during grapevine abscission and also suggest that this could be associated with changes in ethylene-related gene expression.

Systemic Resistance to Gray Mold Induced in Tomato by Benzothiadiazole and Trichoderma harzianum T39

Gray mold (Botrytis cinerea) is an important disease of tomato (Solanum lycopersicum). This study examined defense-related gene expression involved in the resistance to B. cinerea that is induced in tomato plants by benzothiadiazole and Trichoderma harzianum T39 soil drench. In whole plants, transcriptional changes related to salicylic acid and ethylene were induced by the application of a 0.01% benzothiadiazole solution, whereas changes related to jasmonic acid were induced by the application of a 0.4% T39 suspension. On detached leaves, soil treatment by T39 led to enhanced resistance to B. cinerea infection that was proportional to the concentration of the T39 suspension. By 5 days after pathogen inoculation, the plants that had received the 0.04% T39 drench exhibited 62% less severe disease than the untreated plants. The 0.4% T39 drench led to an 84% reduction in disease severity. Observations of B. cinerea infection in leaves harvested from plants grown in the treated soils revealed that drenching with a T39 suspension induces systemic resistance against B. cinerea and primes salicylic acid- and ethylene-related gene expression in a manner proportional to the concentration of the biocontrol agent. Benzothiadiazole treatment induced resistance to gray mold independently of salicylic acid and led to strong priming of two genes known to be involved in defense against B. cinerea, Pti5 and PI2.