Search

Heat stress in summer causes softening disorder in papaya but the molecular mechanism is not clear. In this study, papaya fruit stored at 35 °C showed a softening disorder termed rubbery texture. Analysis of the transcriptome and metabolome identified numerous differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) between the fruit stored at 25 °C and 35 °C. The DEGs and DAMs related to lignin biosynthesis were upregulated, while those related to ethylene biosynthesis, sucrose metabolism, and cell wall degradation were downregulated under heat stress. Co-expression network analysis highlighted the correlation between the DEGs and metabolites associated with lignin biosynthesis, ethylene biosynthesis, and cell wall degradation under heat stress. Finally, the correlation analysis identified the key factors regulating softening disorder under heat stress. The study's findings reveal that heat stress inhibited papaya cell wall degradation and ethylene production, delaying fruit ripening and softening and ultimately resulting in a rubbery texture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Chilling stress causes banana fruit softening disorder and severely impairs fruit quality. Various factors, such as transcription factors, regulate fruit softening. Herein, we identified a novel regulator, MaC2H2-IDD, whose expression is closely associated with fruit ripening and softening disorder. MaC2H2-IDD is a transcriptional activator located in the nucleus. The transient and ectopic overexpression of MaC2H2-IDD promoted "Fenjiao" banana and tomato fruit ripening. However, transient silencing of MaC2H2-IDD repressed "Fenjiao" banana fruit ripening. MaC2H2-IDD modulates fruit softening by activating the promoter activity of starch (MaBAM3, MaBAM6, MaBAM8, MaAMY3, and MaISA2) and cell wall (MaEXP-A2, MaEXP-A8, MaSUR14-like, and MaGLU22-like) degradation genes. DLR, Y1H, EMSA, and ChIP-qPCR assays validated the expression regulation. MaC2H2-IDD interacts with MaEBF1, enhancing the regulation of MaC2H2-IDD to MaAMY3, MaEXP-A2, and MaGLU22-like. Overexpressing/silencing MaC2H2-IDD in banana and tomato fruit altered the transcript levels of the cell wall and starch (CWS) degradation genes. Several differentially expressed genes (DEGs) were authenticated between the overexpression and control fruit. The DEGs mainly enriched biosynthesis of secondary metabolism, amino sugar and nucleotide sugar metabolism, fructose and mannose metabolism, starch and sucrose metabolism, and plant hormones signal transduction. Overexpressing MaC2H2-IDD also upregulated protein levels of MaEBF1. MaEBF1 does not ubiquitinate or degrade MaC2H2-IDD. These data indicate that MaC2H2-IDD is a new regulator of CWS degradation in "Fenjiao" banana and cooperates with MaEBF1 to modulate fruit softening, which also involves the cold softening disorder., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

It is well known that calcium, ethylene and abscisic acid (ABA) can regulate fruit ripening, however, their interaction in the regulation of fruit ripening has not yet been fully clarified. The present study found that the expression of the papaya calcium sensor CpCML15 was strongly linked to fruit ripening. CpCML15 could bind Ca 2+ and served as a true calcium sensor. CpCML15 interacted with CpPP2C46 and CpPP2C65, the candidate components of the ABA signalling pathways. CpPP2C46/65 expression was also related to fruit ripening and regulated by ethylene. CpCML15 was located in the nucleus and CpPP2C46/65 were located in both the nucleus and membrane. The interaction between CpCML15 and CpPP2C46/65 was calcium dependent and further repressed the activity of CpPP2C46/65 in vitro. The transient overexpression of CpCML15 and CpPP2C46/65 in papaya promoted fruit ripening and gene expression related to ripening. The reduced expression of CpCML15 and CpPP2C46/65 by virus-induced gene silencing delayed fruit colouring and softening and repressed the expression of genes related to ethylene signalling and softening. Moreover, ectopic overexpression of CpCML15 in tomato fruit also promoted fruit softening and ripening by increasing ethylene production and enhancing gene expression related to ripening. Additionally, CpPP2C46 interacted with CpABI5, and CpPP2C65 interacted with CpERF003-like, two transcriptional factors in ABA and ethylene signalling pathways that are closely related to fruit ripening. Taken together, our results showed that CpCML15 and CpPP2Cs positively regulated fruit ripening, and their interaction integrated the cross-talk of calcium, ABA and ethylene signals in fruit ripening through the CpCML15-CpPP2Cs-CpABI5/CpERF003-like pathway., (© 2024 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.)

Cold stress adversely affects plant production, both qualitatively and quantitatively. Banana (Musa acuminata) is sensitive to cold stress and suffers chilling injury (CI) when stored under 11°C, causing abnormal fruit softening. However, the mechanism underlying the abnormal fruit softening due to CI remains obscure. This study uncovered the coordinated transcriptional mechanism of ethylene F-box (EBF1) protein and abscisic acid-insensitive 5 (ABI5)-like protein in regulating chilling-induced softening disorders of Fenjiao banana. Cold stress severely inhibited the transcript and protein levels of EBF1, ABI5-like, and fruit softening-related genes. The ABI5-like protein bound to the promoters of key starch and cell wall degradation-related genes such as β-amylase 8 (BAM8), pectate lyase 8 (PL8), and β-D-xylosidase23-like (XYL23-like) and activated their activities. EBF1 physically interacted with ABI5-like and enhanced the transcriptional activity of the key starch and cell wall degradation-related genes but did not ubiquitinate or degrade ABI5-like protein. This promoted fruit ripening and ameliorated fruit CI in a manner similar to the effect of exogenous abscisic acid treatment. The ectopic and transient overexpression of EBF1 and ABI5-like genes in tomato (Solanum lycopersicum) and Fenjiao banana accelerated fruit ripening and softening by promoting ethylene production, starch and cell wall degradation, and decreasing fruit firmness. EBF1 interacted with EIL4 but did not ubiquitinate or degrade EIL4, which is inconsistent with the typical role of EBF1/2 in Arabidopsis (Arabidopsis thaliana). These results collectively highlight that the interaction of EBF1 and ABI5-like controls starch and cell wall metabolism in banana, which is strongly inhibited by chilling stress, leading to fruit softening and ripening disorder., (© American Society of Plant Biologists 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Fenjiao (Musa ABB Pisang Awak) is a popular banana cultivar due to its good taste and stress resistance, but it has a short shelf-life and deteriorates rapidly post-harvest. The effects of 1-methylcyclopropene (1-MCP) treatment on fruit physiology and quality and transcriptomic profiles are investigated in this study. The results showed that 1-MCP significantly delayed fruit ripening by repressing fruit softening and inhibiting the respiratory rate and ethylene production. The 1-MCP treatment delayed sugar accumulation and influenced the content of the precursors of the biosynthesis of aroma volatiles. 1-MCP reduced the production of flavor-contributing volatile esters isoamyl isobutyrate, isoamyl acetate and trans-2-hexenal and hexanal, but dramatically increased the hexyl acetate production at the full-ripening stage. The transcriptomic analysis showed that 1-MCP dramatically affected the transcript profiles during fruit ripening, especially the KEGG pathways involved in amino acid metabolism, biosynthesis of other secondary metabolites, carbohydrate metabolism, lipid metabolism, signal transduction, and translation classes. The key genes and the corresponding enzyme activities involved in the volatile and ethylene synthesis were severely repressed due to the 1-MCP treatment. The 1-MCP treatment effectively delayed Fenjiao fruit ripening, but affected volatile production by reducing the precursor production and expression level of genes involved in the metabolism pathways of ethylene, auxin and volatiles., Competing Interests: Declaration of Competing Interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Aromatic compounds are important for fruit quality and can vary among fruit cultivars. Volatile compounds formed during the ripening of two banana cultivars, Brazilian and Fenjiao, were determined using headspace solid-phase micro-extraction (SPME) and gas chromatography coupled with mass spectrometry (GC-MS). These two cultivars exhibited different physiological characteristics during storage. Fenjiao fruit exhibited faster yellowing and softening, a higher respiration rate and greater ethylene production. Also, the soluble sugar content in Fenjiao fruit was much higher than in Brazilian fruit. In total, 62 and 59 volatile compounds were detected in Fenjiao and Brazilian fruits, respectively. The predominant volatile components isoamyl acetate, butanoic acid, 3-methyl-3-methylbutyl ester, hexanal, trans -2-hexenal and 1-hexanol varied during ripening stages. Moreover, esters were more abundant in Fenjiao, and propanoic acid 2-methylbutyl ester, and octanoic acid were only detected in Fenjiao. These compounds contribute to the unique flavors and aromas of the two cultivars.

Benzothiadiazole (BTH) works as a plant activator. The effects of different BTH treatments and fungicides SPORGON on fruit ripening and disease incidence were investigated. The results showed that BTH treatment significantly delayed fruit ripening, maintained fruit firmness, color, and good fruit quality, and dramatically reduced the incidence of disease. BTH effectively inhibited the invasion and development of pathogenic bacteria and controlled the occurrence of disease. BTH treatment enhanced the activities of defense-related enzymes, including chitinase, phenylalanine ammonia-lyase, peroxidase, and polyphenol oxidase, increased the content of hydrogen peroxide and total antioxidant capacity, and reduced malondialdehyde content. Cellular structure analysis after inoculation confirmed that BTH treatment effectively maintained the cell structural integrity. SPORGON did not provide benefits for delaying fruit ripening or for the resistance system, while it can control the disease only during the earlier stage and not at later stages.

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.

Ethylene response factors (ERFs) play important roles in fruit development, ripening, defense responses and stress signaling pathways. After harvest, climacteric fruit such as papaya are subject to a range of problems associated with postharvest handling and storage treatments. There have been few attempts to evaluate the role of ERFs in fruit's responses to environmental stimuli. To investigate the transcriptional mechanisms underlying fruit developmental, ripening and stresses, we cloned four ERFs from papaya. The deduced amino acid sequence of CpERFs contained the conserved apetalous (AP2)/ERF domain, which shared high similarity with other reported AP2/ERF domains. The phylogeny, gene structures, and putatively conserved motifs in papaya ERF proteins were analyzed, and compared with those of Arabidopsis. Expression patterns of CpERFs were examined during fruit development, under 1-MCP treatment, ethephon treatment, biotic stress (temperature stress) and pathogen stress. CpERFs displayed differential expression patterns and expression levels under different experimental conditions. CpERF2 and CpERF3 showed a close association with fruit ripening and CpERFs had a high expression level in the earlier stages during the fruit development period. The expression of CpERFs strongly associated with stress response. These results support the role for papaya ERFs in transcriptional regulation of ripening-related or stress-respond genes and thus, in the regulation of papaya fruit-ripening processes and stress responses., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)

Background: Biological control is a potential strategy to reduce post-harvest decay in several fruits. Little research has been carried out on the effects of endophytic bacterium on post-harvest blight caused by Phytophthora nicotianae in papaya. In this work, the biocontrol activity of Pseudomonas putida MGP1 on this disease and its possible mechanisms, including changes of defensive enzyme activities, total phenolic content and mRNA levels of two important genes, were investigated., Results: Fruits treated with MGP1 showed a significant lower disease index and demonstrated increases in chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase, peroxidase, polyphenol oxidase and catalase activities and total phenolic content. In addition, the expression levels of pathogenesis related protein 1 gene (PR1) and non-expressor of PR1 gene (NPR1) in papaya fruits were elevated by MGP1 treatment. CONCLUSION The results indicated that papaya fruits were responsive to the endophytic bacterium Ps. putida, which could activate defensive enzymes and genes and thereby induce host disease resistance., (Copyright © 2012 Society of Chemical Industry.)

Pineapple (Ananas comosus (L.) Merr. cv. 'Paris') is sensitive to low temperature and highly susceptible to blackheart during cold storage, which causes serious fruit decay. This work investigated the effect of wax treatment (Sta-Fresh 2952, 60 g/L) on blackheart of pineapple under chilling stress. Wax treatment significantly reduced blackheart symptoms after 14 days of storage and markedly delayed changes in firmness and flesh color during the whole period of storage. The weight loss of wax-treated fruit (2.6%) was less than the control (3.1%) at the 24th day of storage. The treatment decreased the activities of PG and EGase for maintaining cell wall stability during the later period of storage. In the control fruit, the structure of flesh cells was significantly damaged under chilling stress, with looser cell wall, absence of middle lamella, loss of membrane integrity, and many cells near the vascular tissue collapsed. The subcellular elements could be barely observed in the control after storage. These destructive symptoms were significantly alleviated in the wax-treated fruit. The results suggest that wax treatment could reduce blackheart of pineapple under chilling stress via maintenance of cell integrity.

Background: Traditional approaches to the control of diseases of papaya fruit rely on the use of synthetic chemicals, which can cause serious human health and environmental problems. Endophytes might be used as an alternative to chemicals to effectively control diseases of harvested papaya fruit., Results: MGP1 was one of the biological control agents that was selected from the pericarp of papaya and identified as Pseudomonas putida biovar A. The bacterium was able to colonise in the lamina, leafstalk, pericarp and pulp of papaya and strongly inhibit ten kinds of phytopathogen. Positive control effects were achieved when fruits were challenged with Phytophthora nicotianae at 24 and 48 h after MGP1 treatment. The control effect of MGP1 on anthracnose of harvested papaya fruit reached 54%. The application of MGP1 at five preharvest stages of papaya significantly reduced the disease index of anthracnose, with the best control effect reaching 63% after application at the florescence stage. However, the rate of latent infection of Colletotrichum gloeosporioides was significantly reduced only after application at the fluorescence stage., Conclusion: The results indicated the powerful ability of MGP1 as a biological agent., ((c) 2009 Society of Chemical Industry.)

In the ethylene signalling pathway, EIN2 is an essential signal transducer linking ethylene perception on endoplasmic reticulum to transcriptional regulation in the nucleus, EIN3/EIL1 transcription factors initiate various responses leading to an ethylene response, and EBFs function in ethylene perception by regulating EIN3/EIL1 turnover. In this work, we isolated and characterised three EIN3 homologs (CpEIN3a, CpEIN3b, and CpEIL1), and two EBF homologs (CpEBF1 and CpEBF2) from papaya fruits. During the fruit development, the transcripts of all these genes were accumulated at a low level before reaching a maximum in the third month, then showed a decrease. Exogenous ethylene application and 1-MCP treatment had different effects on the expression of these genes. The correlations between various physiological characteristics with the gene expressions showed that CpEIN3b, CpEIL1, and CpEBF1/2 were negative regulators in terms of papaya fruit ripening under exogenous ethylene treatment while CpEIN3a was a positive one, CpEIN3a was negatively correlated with the respiration rate and ethylene production of papaya fruits under 1-MCP treatment. It is suggested that CpEIN2, CpEIN3a/b, CpEIL1, and CpEBF1/2 are development- and ripening-related genes in papaya fruits. These results provide new insights into the understanding of the ethylene signalling cascade in papaya fruit development and ripening. [ABSTRACT FROM AUTHOR]

Papaya fruits ripen and deteriorate rapidly after harvest. It is well established that the calcium treatment delays fruit ripening. However, the regulation of fruit ripening by calcium treatment in papaya remains unclear. In the present study, we investigate the effect of calcium chloride treatment (2.5% CaCl2 solution immersion for 15 min), which significantly delayed the ripening of papaya fruit. Fruit yellowing was delayed by 4 days in CaCl2‐treated fruits compared with control. CaCl2 treatment significantly delayed loss in fruit firmness and an increase in the total soluble solid content, relative conductivity, and ethylene peak, as well as reduced ethylene production. It inhibited the activity of cell wall degrading enzymes and the expression of cell wall softening‐related genes and ethylene signal pathway‐related genes. These findings indicate that the CaCl2 treatment delays the ripening and softening of papaya fruits by inhibiting the expression of enzymes and genes related to cell wall degradation and ethylene signal transduction. Practical applications: Papaya is an economically important fruit crop cultivated worldwide. These fruits ripen and deteriorate rapidly after harvest. Calcium chloride treatment (2.5% CaCl2 solution immersion for 15 min) studied in the present study significantly delayed the ripening of papaya fruit. The calcium treatment is easy to operate and control and is effective in maintaining fruit quality and reducing postharvest losses of papaya. It is a safe and non‐toxic alternative to chemical treatment for fruit storage and transportation. [ABSTRACT FROM AUTHOR]

Guava fruit has a short postharvest shelf life at room temperature. Melatonin is widely used for preservation of various postharvest fruit and vegetables. In this study, an optimal melatonin treatment (600 μmol·L−1, 2 h) was identified, which effectively delayed fruit softening and reduced the incidence of anthracnose on guava fruit. Melatonin effectively enhanced the antioxidant capacity and reduced the oxidative damage to the fruit by reducing the contents of superoxide anions, hydrogen peroxide and malondialdehyde; improving the overall antioxidant capacity and enhancing the enzymatic antioxidants and non-enzymatic antioxidants. Melatonin significantly enhanced the activities of catalase, superoxide dismutase, ascorbate peroxidase and glutathione reductase. The contents of total flavonoids and ascorbic acid were maintained by melatonin. This treatment also enhanced the defense-related enzymatic activities of chitinase and phenylpropanoid pathway enzymes, including phenylalanine ammonia lyase and 4-coumaric acid-CoA-ligase. The activities of lipase, lipoxygenase and phospholipase D related to lipid metabolism were repressed by melatonin. These results showed that exogenous melatonin can maintain the quality of guava fruit and enhance its resistance to disease by improving the antioxidant and defense systems of the fruit. [ABSTRACT FROM AUTHOR]

Chilling injury (CI) severely affects the transportation, storage, and marketing of fruit. Papaya is a typical tropical/subtropical fruit susceptible to CI. Generally, fruit stored below 12 °C exhibit CI symptoms and softening disorder after returning to room temperature. In this study, papaya stored at 7 °C showed slight injury after 15 d and severe injury after 25 d, while no CI occurred under 12 °C storage. Transcriptome analysis identified 7710 differential expressed genes (DEGs) between fruit stored at 7 °C and 12 °C. Further KEGG analysis revealed that these DEGs mainly enriched pathways associated with folding, sorting and degradation, lipid metabolism, carbohydrate metabolism, and biosynthesis of other secondary metabolites. Besides, we found that 69 DEGs with expression patterns highly correlated with the CI were associated with lignin synthesis, cellulose, hemicellulose, and pectin degradation pathways and subsequently screened out eight intermediate metabolites of these pathways. The low-temperature storage induced CI inhibited the degradation of lignin, cellulose and total pectin. Further metabolome analysis identified 198 differentially accumulated metabolites (DAMs) between the fruit at 7 °C and 12 °C at 25 d of storage. Metabolic pathways enriched by these DAMs included phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, starch and sucrose metabolism, and plant hormone signal transduction. Weighted gene co-expression network analysis (WGCNA) identified five transcription factors (RAP2–7, bHLH74, AGL9, MYB33 , and SRM1-like) and their predicted downstream target genes closely related to fruit softening. Finally, RT-qPCR analysis of 15 genes validated the transcriptome sequencing data. Thus, our findings collectively prove that CI severely represses the expression of key TFs and their target genes involved in cellulose, hemicellulose, and pectin degradation and their metabolic pathways, resulting in the softening disorder. • Chilling injury affects papaya fruit quality and induced ripening disorder. • Transcriptome analysis identified a group of genes involved in the ripening disorder. • Metabolome and transcriptome analysis revealed the key pathways in ripening disorder. • Five TFs and the predicted targets were screened out and related to fruit softening. [ABSTRACT FROM AUTHOR]

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. At the same time , MaIAA17-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. • Cold stress severely affects the banana fruit softening and de-greening. • MaIAA17-like expression is closely related to fruit ripening/ripening disorder. • MaIAA17-like regulated the activities of promoters of ripening-related genes. • MaIAA17-like interacted with MaEBF1 and regulate ripening-related genes. • The overexpression/silencing of MaIAA17-like promote/inhibit fruit ripening. [ABSTRACT FROM AUTHOR]