Effect of storage temperature on development of chilling injury and its transcriptome analysis in 'Fuyu' persimmon fruit with or without 1-MCP treatment

'Fuyu' persimmon fruit are well known to develop chilling injury (CI) symptoms during cold storage. In this study, we investigated the development of CI and associated transcriptome changes in response to ethylene, 1-methylcyclopropene (1-MCP), and different storage temperatures. Fruit treated with ethylene (at 25°C) softened within 3 d. Fruit stored at 5°C developed CI symptoms, (i.e., flesh softening with induction of ethylene production) within 14-21 d. Fruit at 5°C with repeated 1-MCP treatments maintained high firmness but developed CI symptoms (i.e., rubbery texture) after 28 d. During storage at 15 and 25°C, fruit did not soften for 28 d, regardless of repeated 1-MCP treatments. Subsequent transcriptome analysis resulted in 12 gene clusters, which displayed specific expression patterns in response to ethylene and/or storage temperature. For instance, the expression of cell wall degradation-associated genes PG (polygalacturonase) and BGAL1 (beta-galactosidase 1) was stimulated both by ethylene treatment, and during storage at 5°C. Stimulation of BGAL1 expression at 5°C was, however, not suppressed by 1-MCP treatment. Additionally, the expression of BGL7 (glucan endo-1,3-beta-glucosidase 7), which is also associated with cell wall degradation, increased during storage at 5°C with or without 1-MCP treatment. Two genes encoding transcription factors NAC104 and HAI3 showed increased expression levels during low temperature storage but did not respond to ethylene treatment. These results suggest that CI-related softening in 'Fuyu' persimmon fruit is regulated by both ethylene-dependent and -independent factors.