Hypoxia‐responsive ERFs involved in postdeastringency softening of persimmon fruit

Abstract

SummaryRemoval of astringency by endogenously formed acetaldehyde, achieved by postharvest anaerobic treatment, is of critical importance for many types of persimmon fruit. Although an anaerobic environment accelerates de‐astringency, it also has the deleterious effect of promoting excessive softening, reducing shelf life and marketability. Some hypoxia‐responsive ethylene response factors (ERFs) participate in anaerobic de‐astringency, but their role in accelerated softening was unclear. Undesirable rapid softening induced by high CO 2 (95%) was ameliorated by adding the ethylene inhibitor 1‐MCP (1 μL/L), resulting in reduced astringency while maintaining firmness, suggesting that CO 2‐induced softening involves ethylene signalling. Among the hypoxia‐responsive genes, expression of eight involved in fruit cell wall metabolism (Dkβ‐gal1/4, DkEGase1, DkPE1/2, DkPG1, DkXTH9/10) and three ethylene response factor genes (DkERF8/16/19) showed significant correlations with postdeastringency fruit softening. Dual‐luciferase assay indicated that DkERF8/16/19 could trans‐activate the DkXTH9 promoter and this interaction was abolished by a mutation introduced into the C‐repeat/dehydration‐responsive element of the DkXTH9 promoter, supporting the conclusion that these DkERFs bind directly to the DkXTH9 promoter and regulate this gene, which encodes an important cell wall metabolism enzyme. Some hypoxia‐responsive ERF genes are involved in deastringency and softening, and this linkage was uncoupled by 1‐MCP. Fruit of the Japanese cultivar ‘Tonewase’ provide a model for altered anaerobic response, as they lost astringency yet maintained firmness after CO 2 treatment without 1‐MCP and changes in cell wall enzymes and ERFs did not occur.

DkNAC7, a novel high-CO2/hypoxia-induced NAC transcription factor, regulates persimmon fruit de-astringency

“…The above-mentioned regulatory effects of DkNAC7 on deastringency related genes encouraged us to study the response of DkNAC7 to deastringency treatment. From previous results, AHCA treatment (also called CO 2 treatment or high CO 2 treatment: 95% CO 2 and 1% O 2 ) was very effective in removing astringency in various persimmon [ 5 , 7 , 21 ]. Therefore, using previously described materials [ 21 ], the expression of DkNAC7 was analyzed.…”

“…From previous results, AHCA treatment (also called CO 2 treatment or high CO 2 treatment: 95% CO 2 and 1% O 2 ) was very effective in removing astringency in various persimmon [ 5 , 7 , 21 ]. Therefore, using previously described materials [ 21 ], the expression of DkNAC7 was analyzed. The DkNAC7 gene exhibited a sharp increase in expression in response to AHCA treatment, with the highest level at 1 d ( Fig 4 ).…”

“…kaki ) fruit were obtained from a commercial orchard at Fangshan (Beijing, China) in 2012. Fruit without disease or mechanical wounding were selected and treated with artificial high-CO 2 atmosphere (AHCA, 95% CO 2 and 1% O 2 ) or air in air-tight containers for 1 d. The physiological data and sampling information were described in Wang et al [ 21 ].…”

Hydrogen Sulfide Inhibits Fruit Softening by Regulating Ethylene Synthesis and Signaling Pathway in Tomato (Solanum lycopersicum)

“…For instance, the expression of CWDE is ethylene-dependent; therefore, fruit softening and cell wall disassembly are regulated by ethylene in Charentais melon (Nishiyama et al, 2007). The ERF DkERFs in persimmon fruit was found to directly bind to the promoter of a CWDE gene DkXTH9 and regulate its gene expression (Wang et al, 2017). Therefore, the role of H 2 S in regulating fruit softening could be as a linear signaling pathway (H 2 S-ethylene-CWDE).…”

Progress toward Understanding the Molecular Basis of Fruit Response to Hypoxia

“…Recently, Meitha et al identified three ERF-VIIs in grape berries, which are substrates for oxygen-dependent N-end rule proteolysis as in Arabidopsis [81]. Additionally, several hypoxia-responsive ERFs were shown to be directly involved in transcriptional regulation of anaerobic metabolism genes involved in persimmon deastringency [82,83,84]; however, their possible oxygen-dependent regulation via the N-end rule pathway is still unknown. Although it is worth noting that DkERF10, based on an amino acid sequence, could be a candidate substrate of the N-end rule pathway of protein degradation.…”