Climacteric ripening of apple fruit is regulated by transcriptional circuits stimulated by cross-talks between ethylene and auxin

Abstract

Apple is a fleshy fruit distinguished by a climacteric type of ripening, since most of the relevant physiological changes are triggered and governed by the action of ethylene. After its production, this hormone is perceived by a series of receptors to regulate, through a signaling cascade, downstream ethylene related genes. The possibility to control the effect of ethylene opened new horizons to the improvement of the postharvest fruit quality. To this end, 1-methylcyclopropene (1-MCP), an ethylene antagonist, is routinely used to modulate the ripening progression increasing storage life. In a recent work published in The Plant Journal, the whole transcriptome variation throughout fruit development and ripening, with the adjunct comparison between normal and impaired postharvest ripening, has been illustrated. In particular, besides the expected downregulation of ethylene-regulated genes, we shed light on a regulatory circuit leading to de-repressing the expression of a specific set of genes following 1-MCP treatment, such as AUX/IAA, NAC and MADS. These findings suggested the existence of a possible ethylene/auxin cross-talk in apple, regulated by a transcriptional circuit stimulated by the interference at the ethylene receptor level.

Wide transcriptional investigation unravel novel insights of the on-tree maturation and postharvest ripening of ‘Abate Fetel’ pear fruit

“…The remove of ethylene during the climacteric phase induced a de-repression of this gene, in order to restore a normal ripening physiology. Although additional evidences about the involvement of auxin in the triggering of the climacteric ripening are compelling, these transcriptional data suggest the existence of such hormonal cross-talk also in pear, similarly to what has been recently reported for apple 14,45,46 .…”

Decoding altitude-activated regulatory mechanisms occurring during apple peel ripening

“…It is interesting to note that orchard altitude has a profound impact on temperature, light, humidity, and other factors, which have a direct influence on apple peel metabolism. Based on the previous published work in apple fruit 5,6,11,28 as well as on the meteorological data from the two sites studied here ( Supplementary Fig. 1) we can assume that most of the color-related phenotypic variability can be associated with the different air temperature and UV levels, both of which are strongly related to altitude 3,4,7 .…”

“…Many apple fruit quality characteristics appear to be specifically related to only one of the two pericarp tissues. For instance, taste-related traits such as the sugar and acid content mostly depend on the flesh 5 , while the apple peel is the main site in the synthesis of many compounds of interest (e.g. anthocyanins and aroma volatiles), indicating that these tissues undergo specific ripening processes 6 .…”

Identification of Candidate Genes Involved in Fruit Ripening and Crispness Retention Through Transcriptome Analyses of a ‘Honeycrisp’ Population

“…Although the two reports are seemingly contradictory, they both hypothesize that auxin is critical at the onset of fruit ripening. A fruit ripening model for apple established by Busatto et al [ 36 ] demonstrates that after fruit enter advanced ripening stages, auxin-related genes are downregulated along with increased expression of ethylene-related genes. Thus, the higher expression of auxin-related genes observed in this study suggests that fruit of the “Retain” individuals were harvested at relatively early ripening stages.…”