ABSTRACT Ethylene plays a crucial role in fruit ripening and is perceived by specialised receptor proteins embedded in the endoplasmic reticulum (ER) membrane. As an ethylene antagonist, 1‐methylcyclopropene (1‐MCP) binds to these receptors and delays papaya ripening, but improper use can cause ripening disorders. The expression of CpERS1 and CpERF‐WRI1 is markedly upregulated during ripening yet is suppressed by inappropriate 1‐MCP treatments. Similar ripening disorders and expression patterns of CpERS1 and CpERF‐WRI1 were observed in immature, chilled and heat‐stressed papaya fruits, indicating that these genes may play key roles in ripening disorder. CpERF‐WRI1 binds to and activates the CpERS1 promoter both in vitro and in vivo. Transient overexpression of CpERF‐WRI1 in papaya and ectopic expression in tomato accelerated fruit ripening, increased CpERS1 expression and upregulated ripening‐related pathways, whereas virus‐induced gene silencing (VIGS) of CpERF‐WRI1 in papaya delayed ripening and downregulated those pathways. Similarly, overexpressing CpERS1 in papaya and tomato accelerated ripening and boosted the expression of ripening‐associated genes, while VIGS‐mediated silencing of CpERS1 delayed ripening and suppressed these genes. Together, these results indicate that CpERF‐WRI1 regulates CpERS1 expression and modulates ethylene sensing within the system II ethylene signalling pathway to control papaya ripening.
Wu et al. (Mon,) studied this question.