S17 - Session O1 - Chlorophyll breakdown in fruits: The relevance of the senescence-related pheophorbide a oxygenase/phyllobilin (PaO/PB) pathway during ripening and biotic stress.
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Authors: Michael Oberhuber *, Peter Robatscher, Lisa Marie Gorfer
Chlorophyll plays a fundamental role in plants and fruits, and its disappearance is typically associated with senescence due to the autumnal leaf coloring. Chlorophyll breakdown, however, is not limited to senescence: Fruits change color during ripening and early leaf yellowing or chlorosis is a well-studied symptom of biotic and abiotic stress. Recent work on apple ( Malus domestica Borkh.) and other species has shown that chlorophyll is broken down to the same class of metabolites (phyllobilins, PBs) via a common metabolic pathway mediated by pheophorbide a oxygenase (PaO) in all three cases: senescence, ripening and stress. Physiological roles for PBs have been proposed based on their antioxidative properties, and health benefits have been deduced from pharmacological activities, including anti-inflammatory properties and inhibiting activities against cancer cells. To gain a deeper understanding of the breakdown of chlorophyll in fruit species beyond the autumnal leaf yellowing, the abundance, diversity, and emergence of PBs during ripening, stress, and senescence were investigated. We will report on the remarkable variety of PBs in apple and medicinal plants and discuss their possible health benefits for humans, physiological roles in plants and their potential as biomarker for fruit quality.