Research article Oxylipin profile and antioxidant status of potato tubers during extended storage at room temperature Pierre Delaplace 1 , Jorge Rojas-Beltran 1 , Patrick Frettinger, Patrick du Jardin, Marie-Laure Fauconnier * Plant Biology Unit, Gembloux Agricultural University, Passage des De´porte ´s 2, B-5030 Gembloux, Belgium article info Article history: Received 15 April 2008 Accepted 2 September 2008 Available online 18 September 2008 Keywords: Potato Solanum tuberosum L. Oxylipin Aging Fatty acid hydroperoxide Oxidative stress Post-harvest storage abstract Potato tubers (cv. Bintje) (Solanum tuberosum L.) were stored under extreme conditions at 20  C for 350 days without sprout inhibitors in order to assess whether aging- and/or senescence-related processes occurred. Under these extreme storage conditions, multiple sprouting followed by the formation of daughter tubers occurs. At the same time, an increase in respiration intensity, as evidenced by cyto- chrome c oxidase activity (E.C. 1.9.3.1), is observed, leading to a potential increase in reactive oxygen species (ROS) production. As polyunsaturated fatty acids are priority targets of oxidative attacks, the damage to lipids was assessed by oxylipin profiling in both free and esterified forms. Oxylipin profiling showed a predominance of linoleic acid-derived oxylipins and of 9-hydroxy and 9-hydroperoxy fatty acids in both free and esterified forms. No significant accumulation of individual oxylipin was observed 350 days after harvest. To further understand the absence of lipid breakdown products accumulation, the main enzymatic and non-enzymatic antioxidants were assessed. Antioxidant enzyme activities [super- oxide dismutase (E.C. 1.15.1.1), catalase (E.C. 1.11.1.6.), ascorbate peroxidase (E.C. 1.11.1.11)] were enhanced during the advanced phase of aging. The main non-enzymatic antioxidant compound, ascorbate, decreased markedly in the early stages of storage, followed by a slower decline. Total radical scavenging activity was also maintained at the end of the storage period. Our results indicate that the enhanced aging process occurring during storage at room temperature does not seem to be associated with the changes classically encountered during leaf senescence or seed aging and that the observed degenerative processes do not surpass the protective potential of the tubers. Ó 2008 Elsevier Masson SAS. All rights reserved. 1. Introduction Global production of potato (Solanum tuberosum L.) tubers reached 330 million tons in 2004. This crop is the fifth most cultivated plant after sugar cane, maize, rice and wheat [11]. In the main potato-producing countries of the northern hemisphere, potato seed tubers are planted in spring and are harvested at the end of summer. In order to ensure a steady supply to the food market, potato tubers therefore have to be stored for up to 1 year until the next harvest. To improve conservation, they are stored at low temperatures and treated with sprout inhibitors to slow down sprouting-associated quality loss during storage [5]. In contrast, when potato tubers are stored at room temperature without sprout inhibitors, their dormancy is quickly broken. A progressive loss of apical dominance then occurs: initially, a single sprout emerges during the apical dominance period, and then multiple sprouts are produced [12]. If the storage period is prolonged, tuberous swell- ings (‘daughter tubers’) form directly on the sprouts [5]. Apart from their agronomical importance, potato tubers are considered as model organs for studying the aging process because they can retain their sprouting capacity for up to 3 years when stored at low temperatures [48]. Although there have been several studies on potato tuber aging [23,24], it is unclear if typical senescence- or aging-related events potentially occur during storage. At the organ level, aging and senescence are clearly different. For example, a seed ages during post-harvest storage [18] whereas a leaf enters senescence before abscission [4,38]. Aging is due mainly to stochastic degenerative processes driven by external forces (e.g., environmental conditions) that gradually surpass the genetically controlled housekeeping metabolism and its protective potential [3]. In contrast, senescence is defined as a genetically Abbreviations: APX, ascorbate peroxidase; AsA, ascorbate; CAT, catalase; DHA, dehydroascorbate; DAB-stained POX, diaminobenzidine-stained peroxidase; dah, day after harvest; DTT, dithiothreitol; DW, dry weight; HPLC, high performance liquid chromatography; HOD, hydroxy linoleic acid; HOD-Me, hydroxy linoleic acid (esterified); HOT, hydroxy linolenic acid; HOT-Me, hydroxy linolenic acid (esteri- fied); HPOs, fatty acid hydroperoxides; HPOD, hydroperoxy linoleic acid; HPOD-Me, hydroperoxy linoleic acid (esterified); HPOT, hydroperoxy linolenic acid; HPOT-Me, hydroperoxy linolenic acid (esterified); LOX, lipoxygenase; POX, peroxidase; ROS, reactive oxygen species; RSA, radical scavenging activity; SOD, superoxide dis- mutase; Trolox, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid. * Corresponding author. Tel.: þ32 81622460; fax: þ32 81600727. E-mail address: fauconnier.ml@fsagx.ac.be (M.-L. Fauconnier). 1 Pierre Delaplace and Jorge Rojas-Beltran contributed equally to this work. Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy 0981-9428/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.plaphy.2008.09.001 Plant Physiology and Biochemistry 46 (2008) 1077–1084