Transcriptomic analysis reveals key factors in fruit ripening and rubbery texture caused by 1-MCP in papaya

Abstract

Background Ethylene promotes fruit ripening whereas 1-methylcyclopropene (1-MCP), a non-toxic antagonist of ethylene, delays fruit ripening via the inhibition of ethylene receptor. However, unsuitable 1-MCP treatment can cause fruit ripening disorders. Results In this study, we show that short-term 1-MCP treatment (400 nL•L − 1 , 2 h) significantly delays papaya fruit ripening with normal ripening characteristics. However, long-term 1-MCP treatment (400 nL•L − 1 , 16 h) causes a “rubbery” texture of fruit. The comparative transcriptome analysis showed that a total of 5529 genes were differently expressed during fruit ripening compared to freshly harvested fruits. Comprehensive functional enrichment analysis showed that the metabolic pathways of carbon metabolism, plant hormone signal transduction, biosynthesis of amino acids, and starch and sucrose metabolism are involved in fruit ripening. 1-MCP treatment significantly affected fruit transcript levels. A total of 3595 and 5998 differently expressed genes (DEGs) were identified between short-term 1-MCP, long-term 1-MCP treatment and the control, respectively. DEGs are mostly enriched in the similar pathway involved in fruit ripening. A large number of DEGs were also identified between long-term and short-term 1-MCP treatment, with most of the DEGs being enriched in carbon metabolism, starch and sucrose metabolism, plant hormone signal transduction, and biosynthesis of amino acids. The 1-MCP treatments accelerated the lignin accumulation and delayed cellulose degradation during fruit ripening. Considering the rubbery phenotype, we inferred that the cell wall metabolism and hormone signal pathways are closely related to papaya fruit ripening disorder. The RNA-Seq output was confirmed using RT-qPCR by 28 selected genes that were involved in cell wall metabolism and hormone signal pathways. Conclusions These results showed that long-term 1-MCP treatment severely inhibited ethylene signaling and the cell wall metabolism pathways, which may result in the failure of cell wall degradation and fruit softening. Our results reveal multiple ripening-associated events during papaya fruit ripening and provide a foundation for understanding the molecular mechanisms underlying 1-MCP treatment on fruit ripening and the regulatory networks. Electronic supplementary material The online version of this article (10.1186/s12870-019-1904-x) contains supplementary material, which is available to authorized users.

Effect of 1‐MCP coupling with carbon dioxide treatment on antioxidant enzyme activities and quality of fresh‐cut Fuji apples

“…Moreover, firmness loss of apples in the treatment group rose significantly ( p < .05) compared with the control group. In previous experiments, different varieties of apples were harder than untreated apples after being treated with 1‐MCP (Fan, Blankenship, & Mattheis, 1999; Rupasinghe, Murr, Paliyath, & Skog, 2000; Watkins & Nock, 2005; Watkins, Nock, & Whitaker, 2000; Zhu et al, 2019). This may be due to that the carbon dioxide injured of fruit and the mechanical damage of fresh‐cut apples during processing and storage (Fawbush et al., 2008; Martino, Vizovitis, Botondi, Bellincontro, & Mencarelli, 2006).…”

Transcriptome profiling helps to elucidate the mechanisms of ripening and epidermal senescence in passion fruit (Passiflora edulia Sims)

“…In addition to ROS, other signaling pathways or molecules are also involved in plant senescence, including plant hormone transduction, ethylene, auxin, jasmonic acid and salicylic acid [39]. Plant hormones are indispensable in the regulation of fruit ripening and senescence, which control fruit color, sugar, flavor and aroma during ripening and senescence [40]. A previous study reported that ethylene and auxin play a major role in the ripening and senescence process of climacteric fruits [41].…”

“…Cell wall degradation is essential for fruit quality during fruit ripening and the senescence process [40]. The thickness and strength of the cell wall are key components for maintaining fruit firmness [48].…”

Transcriptome profiling reveals the mechanism of ripening and epidermal senescence in passion (Passiflora edulia Sims) fruit

“…Besides ROS, other signaling pathways or molecular are also involved in plant senescence, including plant hormones transduction, ethylene, auxin, jasmonic acid and salicylic acid [39] . Plant hormones are indispensable to regulate fruit ripening and senescence, which controlled fruit color, sugar, flavor and aroma during ripening and senescence [40] . And previous study reported that ethylene and auxin were plays a major role in the ripening and senescence process of climacteric fruits [41] .…”

“…Cell wall degradation is essential for fruit quality during the fruit ripening and the senescence process [40] . The thickness and strength of cell wall are key components to maintenance the fruit firmness [48] .…”