Systems Biology Applied to the Study of Papaya Fruit Ripening: The Influence of Ethylene on Pulp Softening

Abstract

Papaya is a fleshy fruit that undergoes fast ethylene-induced modifications. The fruit becomes edible, but the fast pulp softening is the main factor that limits the post-harvest period. Papaya fast pulp softening occurs due to cell wall disassembling coordinated by ethylene triggering that massively expresses pectinases. In this work, RNA-seq analysis of ethylene-treated and non-treated papayas enabled a wide transcriptome overview that indicated the role of ethylene during ripening at the gene expression level. Several families of transcription factors (AP2/ERF, NAC, and MADS-box) were differentially expressed. ACO, ACS, and SAM-Mtase genes were upregulated, indicating a high rate of ethylene biosynthesis after ethylene treatment. The correlation among gene expression and physiological data demonstrated ethylene treatment can indeed simulate ripening, and regulation of changes in fruit color, aroma, and flavor could be attributed to the coordinated expression of several related genes. Especially about pulp firmness, the identification of 157 expressed genes related to cell wall metabolism demonstrated that pulp softening is accomplished by a coordinated action of several different cell wall-related enzymes. The mechanism is different from other commercially important fruits, such as strawberry, tomato, kiwifruit, and apple. The observed behavior of this new transcriptomic data confirms ethylene triggering is the main event that elicits fast pulp softening in papayas.

Molecular and Genetic Events Determining the Softening of Fleshy Fruits: A Comprehensive Review

“…For example, exogenous treatments with ETH can rapidly reduce the firmness of kiwifruit and strawberry fruit by inducing CkPGC and FaPG1 gene expressions [ 85 , 86 ]. ETH treatments also accelerated the softening of papaya and apricot fruits due to cell wall decompositions, while ethylene receptor inhibitor (1-methylcyclopropene, 1-MCP) can delay fruit softening by inhibiting the expression of genes related to cell wall degradation [ 87 , 88 ]. The silencing of the genes of key enzymes of system II ethylene biosynthesis in tomatoes, such as SlACS2 , SlACS4 , SlACO1 and SlACO3 , significantly inhibited fruit softening [ 89 ].…”

Assessment of Himalayan plain mango genotypes for phytochemicals, biochemical‐nutraceutical characterisation and quality change during storage life

“…Irrespective of genotypes, TCC increased up to 6th of day storage then declined thereafter steadily. Such pattern might be due to the positive correlation between the synthesis of carotenoid pigment with fruit ripening (Soares et al ., 2021; Prasad et al ., 2022b). The carotenoids provide a natural colour to the pulp in ripe mango fruits and offer various health benefits in addition to being used in pulp blending (Ram et al ., 2017).…”

Plant extract and essential oil coating prolongs shelf life and maintains keeping quality of papaya fruit during storage

“…Irrespective of treatments, total carotenoid content has increased with progress in the storage period, which might be due to direct relation between carotenoid (pigment) synthesis and ripening (Parven et al, 2020; Soares et al, 2021). Among the attempted treatments, the highest total carotenoid content (3.22 mg 100 g −1 FW) was exhibited by “TLE (1% v/v)” treated fruits, while the untreated (control) fruits exhibited the least total carotenoid content (2.97 mg 100 g −1 FW) (Table 2).…”