Differential low oxygen response and transcriptomic shifts drive fresh-cut lettuce deterioration in modified atmosphere packaging

Authors: PENG, HUI - University Of California; LAVELLE, DEAN - University Of California; TRUCO, MARIA JOSE - University Of California; MICHELMORE, RICHARD - University Of California; Simko, Ivan

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2025
Publication Date: 4/10/2025
Citation: Peng, H., Lavelle, D.O., Truco, M., Michelmore, R.W., Simko, I. 2025. Differential low oxygen response and transcriptomic shifts drive fresh-cut lettuce deterioration in modified atmosphere packaging. Postharvest Biology and Technology. 227. Article 113571. https://doi.org/10.1016/j.postharvbio.2025.113571.
DOI: https://doi.org/10.1016/j.postharvbio.2025.113571

Interpretive Summary: Fresh-cut lettuce is widely enjoyed for its crisp, nutritious qualities but can spoil quickly, leading to waste. To extend its freshness, lettuce is often packaged in a low-oxygen environment, which helps reduce spoilage by slowing down certain chemical reactions. However, some lettuce still spoils faster than others under these conditions. This study investigates how different cultivars of lettuce, specifically Salinas 88 and La Brillante, respond to low-oxygen packaging. It was found that while Salinas 88 had a low rate of respiration, or breathing, at low oxygen, La Brillante had a high rate of respiration, causing it to spoil faster. By analyzing gene activity, differences in energy usage between these types were discovered. The slower-spoiling Salinas 88 conserves energy better, while La Brillante keeps up a high energy demand, leading to quicker spoilage. This insight may help growers and packagers select lettuce types that stay fresher longer, reducing waste and improving quality for consumers.

Technical Abstract: Fresh-cut lettuce (Lactuca sativa) requires modified atmosphere packaging (MAP) with low oxygen (< 3% O2) to prevent enzymatic discoloration on cut surfaces. However, some accessions deteriorate rapidly under low oxygen, increasing product loss and the risk of human pathogen proliferation. Although mechanisms underlying this rapid, heritable deterioration remain unclear, a key locus (qSL4) on chromosome 4 has been identified. Our study links rapid deterioration to sustained respiration under very low O2 (<1%), with minimal effects from CO2 (0-14%) and ethylene (0-10 ppm). Differences in deterioration rates among accessions lessen at higher O2 levels (~20%), highlighting oxygen's concentration impact. RNAseq analysis of slowly (Salinas 88) and rapidly (La Brillante) deteriorating cultivars reveals early transcriptomic shifts: La Brillante upregulates more genes (1,837) and downregulates fewer (1,735) than Salinas 88 (1,185 upregulated, 2,367 downregulated). Candidate genes within qSL4 involved in rapid deterioration rate include RPM1 and a glycosyltransferase. Additionally, glycolysis and electron transport chain (ETC) genes differ in expression, with ATP-consuming enzymes (fructokinase, hexokinase) and ETC complexes I and IV upregulated in La Brillante but downregulated in Salinas 88. In contrast, Salinas 88 shows higher expression of alternative oxidase genes to conserve ATP and reduce oxygen use. These findings imply that slow-deteriorating genotypes like Salinas 88 maintain quality longer under low oxygen by reducing sugar and ATP consumption, while genotypes like La Brillante sustain high metabolic activity, thus accelerating deterioration.