Abstract
A hypoxic environment is generally undesirable for most plants and stimulates anaerobic metabolism. It is a beneficial treatment, however, for the removal of astringency from persimmon to improve the fruit quality after harvest. High soluble tannins (SCTs) content is one of most important causes of astringency. High CO2 (95%) treatment effectively reduced SCTs in both “Mopan” and “Gongcheng-shuishi” persimmon fruit by causing increases in acetaldehyde. Using RNA-seq and realtime PCR, twelve ethylene response factor genes (DkERF11-22) were isolated and characterized, to determine those responsive to high CO2 treatment. Only two genes, DkERF19 and DkERF22, showed trans-activation effects on the promoters of deastringency-related genes pyruvate decarboxylase genes (DkPDC2 and DkPDC3) and the transcript levels of these genes was enhanced by hypoxia. Moreover, DkERF19 and the previously isolated DkERF9 had additive effects on activating the DkPDC2 promoter. Taken together, these results provide further evidence that transcriptome changes in the level of DkERF mRNAs regulate deastringency-related genes and their role in the mechanism of persimmon fruit deastringency is discussed.
Highlights
Low oxygen is a common abiotic stress in plant developmental physiology, which is mainly caused by flooding/submerge
Were isolated, among which DkERF9 and DkERF10 functioned as transcriptional activators of ADH and PDC promoters [12,13]
Phylogenetic analysis of the deduced amino acid sequences showed that the 12 ERF genes were clustered into seven subfamilies, DkERF11 was very close to DkERF1 in subfamily I, DkERF12 and DkERF13 belong to subfamily II, DkERF14 and DkERF15 belong to subfamily III, DkERF16 belongs to subfamily V, DkERF17 -19 and DkERF20-22 were clustered in subfamilies IX and X, respectively (Fig. 1)
Summary
Low oxygen is a common abiotic stress in plant developmental physiology, which is mainly caused by flooding/submerge. On the contrary reduced oxygen concentration is beneficial for some fruit quality traits, eg. Controlled Amosphere (CA) storage with low oxygen level prolongs storage life and maintains fruit quality [1,2]. Besides CA storage, one interesting additional advantage of low oxygen improvement of fruit quality occurs in persimmon fruit (Diospyros kaki), where it removes undesirable astringency. CTs are colourless polyphenolic compounds important both for the plant and human, the soluble part of CTs (SCTs) make an important adverse contribution to fruit taste by causing astringency [3,4]. High CO2 treatment (with reduced oxygen level) and to a lesser extent ethylene treatment, leads to anaerobic fermentation in persimmon fruit, triggering acetaldehyde metabolism [7,8,9]. Acetaldehyde plays important roles in polymerization of SCTs, converting them to insoluble condensed tannins (InSCTs) [10,11]
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