Proline has been shown to accumulate in plant under various type of stresses. In our previous study, changes in cold hardiness and proline content showed contrasting patterns during a constant deacclimation. This study was performed to investigate the proline accumulation and related gene expression in response to repeated deacclimation and reacclimation in peach cultivar ‘Daewol’. Proline content was analyzed using the ninhydrin method and related gene expressions were examined using quantitative real-time RT-PCR. Proline contents of ‘Daewol’ increased during the repeated deacclimation treatments. Interestingly, during the twice deacclimation, expressions of P5CS (Δ1-pyrroline-5-carboxylatesynthase) constantly decreased, whereas expressions of P5CR (Δ1-pyrroline-5-carboxylatereductase) increased. Expressions of OAT (ornithine-δ-aminotransferase) indicated up- and down- pattern in response to repeated deacclimation and reacclimation. Our results indicated that proline responds positively to higher temperature in the shoots of peach cultivar ‘Daewol’ and expressions of both P5CS and P5CR genes could show contrasting patterns during the deacclimation. Moreover, our results suggest that ornithine pathway could serve as an alternative pathway in proline synthesis process during deacclimation in peach.

• Sewon Oh(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Hyunsuk Shin(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Keumsun Kim(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Youngjae Oh(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Jungyeon Won(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Hyeondae Han(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University)
• Daeil Kim(Department of Horticulture, Chungbuk National University, Brain Korea 21 Center for Bio-Resource Chungbuk National University) Corresponding Author