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Summary: 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 Ca2+ 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Heat stress inhibit the ethylene production and delayed the fruit ripening. • Heat stress reduced the enzymes activities related to cell wall (CW) degradation. • Heat stress induced large number of DEGs in cell wall degradation related pathways. • Heat stress induced lignification and inhibit CW degradation, leads to rubbery texture. • Heat stress inhibited the metabolites related to CW degradation. [ABSTRACT FROM AUTHOR]

• 1-MCP + ethylene absorbent (EA) treatment increase shelf-life of 'Fenjiao' banana. • EA does not have the negative effect on the ripening of 'Fenjiao' banana. • 1-MCP+EA repress the enzymes activity related to fruit softening. • 1-MCP +EA modulate the expression of gene related of ripening. • 1-MCP +EA treatment is easy to promote and apply in the banana industry. The 'Fenjiao' banana (Musa ABB Pisang Awak) has a high commercial and nutritional value and is harvested when it is highly plump at between 85 and 90 % commercial maturity. The fruit are less angular at this stage. However, these fruit soften rapidly after harvest. 1-Methylcyclopropene (1-MCP) significantly delays ripening, but it can cause ripening disorders when used improperly. Ethylene absorbent (EA) is also widely used to increase the postharvest life of fruit, but it has less of an effect on 'Fenjiao' banana. This study was conducted to optimize the concentrations of 1-MCP combined with EA to increase the shelf life of these bananas. The results showed that a low concentration of 1-MCP (7 g L−1) combined with EA (2 g kg−1) significantly prolonged the shelf life of the 'Fenjiao' banana and maintained its high quality. The combination of 1-MCP and EA repressed the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase, ACC synthase, pectin methylesterase, polygalacturonase and pectate lyase in the peel and pulp of 'Fenjiao' banana, as well as the corresponding levels of expression of MbACS1, MbACO1, MbPG1, MbPL1 , except for MbPME1 , which are induced by 1-MCP. This study provides a useful technique for preserving 'Fenjiao' fruit with a study on its possible physiological mechanism, which could be applied in the postharvest production of 'Fenjiao' banana. [ABSTRACT FROM AUTHOR]

1-methylcyclopropene (1-MCP) has obvious effects on delaying the ripening of harvested banana fruit. However, improper concentration, treatment time and handling methods could affect normal ripening, yellowing, softening and formation of volatiles, which are important components of banana fruit quality. This study was performed to screen and test the effect of a combination of low concentration ethephon with 1-MCP on the ripening of banana fruit, as well as on physiological and biochemical changes. The results showed that a combination of 50 μL L −1 ethephon with 400 nL L −1 1-MCP (16 h) was the most suitable treatment, which significantly delayed the ripening and maintained the commodity value of harvested banana fruit without detrimentally affecting normal ripening after ripening acceleration treatment. This treatment effectively delayed and decreased respiration rate and ethylene production, inhibited the activity of pectin lyase (PL), pectin methylesterase (PME), cellulase (CX) and polygalacturonase (PG), and delayed the peak activity of ACC synthase (ACS) and ACC oxidase (ACO). It also delayed the formation of volatile compounds, but did not detrimentally affect the amount of volatiles, especially the esters. The combined treatment significantly delayed the ripening and prolonged the shelf life of banana fruit with normal coloring and volatile development, which effectively maintained the commercial value of banana fruit. [ABSTRACT FROM AUTHOR]

Abstract: 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 &y& Elsevier]