# Jasmonates in the Ethylene-Induced Resistance of Detached Citrus Fruits to Peel Damage

## TL;DR

Ethylene pretreatment helps protect citrus fruits from peel damage by influencing jasmonate metabolism and signaling.

## Contribution

The study reveals how ethylene pretreatment affects jasmonate metabolism and signaling to reduce peel damage in detached citrus fruits.

## Key findings

- Ethylene increases genes involved in jasmonate synthesis and signaling.
- Ethylene pretreatment leads to increased levels of jasmonate metabolites like MeJA.
- Ethylene enhances a negative feedback loop in jasmonate signaling, reducing fruit susceptibility to damage.

## Abstract

It is known that nutrient deprivation following detachment can cause non-chilling peel pitting (NCPP) in citrus fruits when stored under a non-stressful environment and that this damage is reduced by pretreating the fruit with ethylene (ETH) (4 d, 10 µL L−1). The present work investigates the effect of this pretreatment on jasmonate (JA) accumulation and transcriptional regulation in mature Navelate oranges (Citrus sinensis L. Osbeck) stored under non-stressful conditions. ETH increased the expression of abundant genes participating in the synthesis of cis-(+)-12-oxo-phytodienoic acid (OPDA), jasmonic acid (JA), and methyl jasmonate (MeJA). ETH also upregulated genes involved in jasmonoyl–isoleucine (JAIle) synthesis (CsJAR1) and decrease (CsCYP94B3 and CYP94C1), and CsSTA2, related to JA sulfation. The levels of these JA metabolites increased during fruit holding in ETH and after shifting them to air, with MeJA accumulation being especially remarkable. Overall, the beneficial effect of ETH on reducing NCPP appears to be related not only to this redirection of OPDA and JA metabolism towards the formation of JA derivatives but also to the regulation of JA signalling. Indeed, the repression of the receptor CsCOI1 and upregulation of various CsJAZs repressors caused by nutrient deprivation, together with the ETH-mediated induction of CsCOI1, CsTOPLESS, and abundant CsJAZs during long-term storage, suggests the occurrence of an ETH-enhanced negative transcriptional regulatory feedback loop in JA metabolism and signalling, by which the susceptibility of detached Navelate oranges to NCPP might be reduced.