INHIBITING PHOSPHOLIPASE A₂ AND D ACTIVITIES ALTERS POSTHARVEST PERFORMANCE OF CITRUS FRUIT

Phospholipases are a wide group of enzymes with lipolytic activity that may trigger lipid signalling and/or phospholipid membrane degradation cascades in response to biotic and abiotic cues, including water stress and pathogen attack, two of the most important causes of losses during postharvest of Citrus fruit.
Phospholipase A₂ (PLA₂) and D activities are induced at transcriptional level during water stress in plants and are involved in loss of quality in certain crops following harvest stress and postharvest storage.
The role of PLA₂ and D as determinants of peel quality was investigated in Citrus fruit by using specific inhibitors, aristolochic acid (AT, a PLA₂ inhibitor) and lysophosphatidyletanolamine (LPE, a PLD inhibitor) during postharvest storage. ‘Navelate’ fruits were stored at low RH (45%) conditions for 3 weeks at 20°C to promote a high rate of evapotranspiration.
Expression of genes encoding PLD and PLA₂ enzymes was analyzed by real time RT-PCR in flavedo.
Data presented show that prolonged dehydration promoted peel disorders and differentially altered CssPLA2β, CsPLDα1 and CsPLDβ1 gene expression.
Interestingly, phospholipase inhibitor treatments promoted phospholipase gene expression, suggesting the existence of feedback mechanisms controlling phospholipase activities.
Inhibiting PLA₂ activity induced a 40% increase in decay incidence, supporting the notion that suppression of oxylipin signalling may reduce the immune response in Citrus fruit.
Besides, PLD inhibition reduced peel brightness, suggesting that epicuticular wax deposition in the fruit surface was altered when the lipid metabolism was disturbed, since waxes are composed by aliphatic compounds including long chain fatty acids, most of them product of phospholipase action.
In both cases, phospholipase inhibitors alleviated water stress-related disorders in peel.
Taken together, data suggest that controlling or modulating phospholipase activities may be beneficial for preserving peel quality during postharvest handling of Citrus fruit.

VI International Postharvest Symposium

F. Alférez, P. Romero, M. Gandía

fruit dehydration, lipid signalling, phospholipase inhibitors, physiological disorders, water stress

https://doi.org/10.17660/ActaHortic.2010.877.103