Molecular and metabolic response of ‘Piccolo’ cherry tomato to Graduated Controlled Atmosphere

Abstract

Controlled atmosphere (CA) is used to extend the postharvest life of climacteric fruit by suppressing respiration and delaying ethylene mediated ripening. However, sudden exposure to low oxygen conditions can induce hypoxic stress, triggering metabolic and hormonal disruptions that negatively impact fruit quality. This study aimed to understand the mechanisms underlying ethylene sensitivity under low oxygen conditions through the application of a novel approach to CA, called Graduated Controlled Atmosphere (GCA), in ‘Piccolo’ cherry tomato. Compared to standard CA, GCA treatment resulted in greater suppression of respiration and improved firmness retention, indicating reduced physiological stress and slower cell wall degradation. Gene expression analysis revealed downregulation of NCED1, ACS, and ACO genes under GCA, indicating delayed ethylene-associated transcriptional activity. These hormonal adjustments were also reflected in lower abscisic acid (ABA) concentrations, implying a more stable ripening trajectory. Besides hormonal modulation, GCA-treated fruit exhibited alterations in primary metabolism. Sucrose accumulation and changes in malate levels under GCA conditions suggest a shift in energy metabolism, consistent with improved hypoxia tolerance. However, a notable trade-off was observed in reduced lycopene accumulation, potentially due to lower oxidative signalling and shared precursors between carotenoid and ABA biosynthesis. These findings demonstrate that GCA promotes a more controlled physiological and molecular response to hypoxic storage by reducing stress-associated metabolic and hormonal activity. GCA, as an advanced postharvest strategy, enhances texture retention and may reduce quality losses during storage. This work provides new mechanistic insights into hypoxia adaptation in fruit and supports the use of gradual atmosphere modification to optimise CA protocols.