Ethylene regulation of fruit softening and cell wall disassembly in Charentais melon

Abstract

Cell wall disassembly in ripening fruit is highly complex, involving the dismantling of multiple polysaccharide networks by diverse families of wall-modifying proteins. While it has been reported in several species that multiple members of each such family are expressed in the same fruit tissue, it is not clear whether this reflects functional redundancy, with protein isozymes from a single enzyme class performing similar roles and contributing equally to wall degradation, or whether they have discrete functions, with some isoforms playing a predominant role. Experiments reported here sought to distinguish between cell wall-related processes in ripening melon that were softening-associated and softening-independent. Cell wall polysaccharide depolymerization and the expression of wall metabolism-related genes were examined in transgenic melon (Cucumis melo var. cantalupensis Naud.) fruit with suppressed expression of the 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene and fruits treated with ethylene and 1-methylcyclopropene (1-MCP). Softening was completely inhibited in the transgenic fruit but was restored by treatment with exogenous ethylene. Moreover, post-harvest application of 1-MCP after the onset of ripening completely halted subsequent softening, suggesting that melon fruit softening is ethylene-dependent. Size exclusion chromatography of cell wall polysaccharides, from the transgenic fruits, with or without exogenous ethylene, indicated that the depolymerization of both pectins and xyloglucans was also ethylene dependent. However, northern analyses of a diverse range of cell wall-related genes, including those for polygalacturonases, xyloglucan endotransglucosylase/hydrolases, expansin, and beta-galactosidases, identified specific genes within single families that could be categorized as ethylene-dependent, ethylene-independent, or partially ethylene-dependent. These results support the hypothesis that while individual cell wall-modifying proteins from each family contribute to cell wall disassembly that accompanies fruit softening, other closely related family members are regulated in an ethylene-independent manner and apparently do not directly participate in fruit softening.

Aminoethoxyvinylglycine: isolated and combined with other growth regulators on quality of ‘Brookfield’ apples after storage

“…In melons (Cucumis melo), the 1-MCP application stopped fruit softening, suggesting that fruit softening is an ethylene-dependent event (Nishiyama et al, 2007). Fruit subjected to ethephon application after AVG had less flesh firmness than the ones that received AVG application only ( Figure 2I).…”

“…Fruit softening is a complex process that involves three steps: the loss of cell wall mediated by expansins, depolymerization of hemicelluloses and polyuronide section by polygalacturonase or other hydrolytic enzymes (Brummell et al, 1999). Thus, fruit subjected to these treatments have less cell wall enzyme activity and ethylene is necessary to initialize this enzyme activity (Nishiyama et al, 2007;Prasanna et al, 2007;Goulao and Oliveira, 2008;Payasi et al, 2009).…”

Osmotic dehydration of yellow melon using red grape juice concentrate

“…The solute gain was the only parameter that showed significant differences, in which there was a lower gain of solute of the most mature melons (Table 3). With the ripening, the melon gets softer, the cell wall gradually collapses, the adhesion wall-wall is decreased and the average blade begins to dissolve (Nishiyama et al, 2007). All these changes alter the permeability of the cell membrane and hence its osmotic dehydration rate (Amami et al, 2007;Panarese et al, 2012;Rastogi et al, 2002).…”

Effect of growth regulators application on the quality maintenance of 'Brookfield' apples

“…Fruits from these treatments presented high levels of flesh firmness, internal space, gas diffusion rate, titratable acidity, soluble solids and healthy fruits. Perhaps, the low IEC, ethylene production and respiration rate in fruits treated with AVG result in lower cell wall degrading enzyme activity, once these enzymes are started by ethylene (Nishiyama et al, 2007;Payasi et al, 2009;Wei et al, 2010), leading in fruits with high flesh firmness and low physiological disorders. The high quality of these fruits is due to the lower ethylene production, respiration rate, IEC and ICO 2 , since great part of these variables have an inverse correlation with quality, especially physiological disorders and gas diffusion rate (Brackmann et al, 2014).…”