High CO2/hypoxia-induced softening of persimmon fruit is modulated by DkERF8/16 and DkNAC9 complexes.

Jing-Wen Huang,Qing-Gang Zhu,Xiao-Fen Liu,Miao-Miao Wang,Hui Gong,Wei Wu,Xue-Ren Yin,Ning-Jing Sun,Kun-Song Chen,Da-Long Guo,Ariel Vicente

doi:10.1093/jxb/eraa009

Abstract

Most persimmon (Diospyros kaki) cultivars are astringent and require post-harvest deastringency treatments such as 95% CO2 (high-CO2 treatment) to make them acceptable to consumers. High-CO2 treatment can, however, also induce excessive softening, which can be reduced by adding 1-methylcyclopropene (1-MCP). Previous studies have shown that genes encoding the ETHYLENE RESPONSE FACTORS (ERFs) DkERF8/16/19 can trans-activate xyloglucan endotransglycosylase/hydrolase (DkXTH9), which encodes the cell wall-degrading enzyme associated with persimmon fruit softening. In this study, RNA-seq data between three treatments were compared, namely high-CO2, high-CO2+1-MCP, and controls. A total of 227 differentially expressed genes, including 17 transcription factors, were predicted to be related to persimmon post-deastringency softening. Dual-luciferase assays indicated that DkNAC9 activated the DkEGase1 promoter 2.64-fold. Synergistic effects on transcription of DkEGase1 that involved DkNAC9 and the previously reported DkERF8/16 were identified. Electrophoretic mobility shift assay indicated that DkNAC9 could physically bind to the DkEGase1 promoter. Bimolecular fluorescence complementation and firefly luciferase complementation imaging assays indicated protein-protein interactions between DkNAC9 and DkERF8/16. Based on these findings, we conclude that DkNAC9 is a direct transcriptional activator of DkEGase1 that can co-operate with DkERF8/16 to enhance fruit post-deastringency softening.

Highlights

IntroductionUsually reflected by firmness, is critical for fruit storability and quality (Brummell, 2006; Li et al, 2010; Wang et al, 2018)
Previous studies have shown that genes encoding the ETHYLENE RESPONSE FACTORS (ERFs) DkERF8/16/19 can trans-activate xyloglucan endotransglycosylase/hydrolase (DkXTH9), which encodes the cell wall-degrading enzyme associated with persimmon fruit softening
We conclude that DkNAC9 is a direct transcriptional activator of DkEGase1 that can co-operate with DkERF8/16 to enhance fruit post-deastringency softening

Summary

Introduction

Usually reflected by firmness, is critical for fruit storability and quality (Brummell, 2006; Li et al, 2010; Wang et al, 2018). Low-oxygen environments, Regulation of fruit softening in persimmon | 2691 usually applied in controlled atmospheres, have been used by industry and researchers to efficiently prolonging postharvest storage and maintenance of firmness in various fruit (McDonald and Harman, 1982; Siddiqui et al, 1996; Yahia, 1998).A particular side effect of high-CO2 (95% CO2, 1% O2, 4% N2) treatment is the accelerated removal of astringency in persimmon (Diospyros kaki) fruit. This greatly improves the taste for consumers, it subsequently triggers rapid softening (Wang et al, 2017), which is undesirable. The mechanism(s) regulating the excessive softening that occurs after deastringency treatment are poorly understood

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Conclusion