Ethylene-related genes show a differential response to low temperature during ‘Hayward’ kiwifruit ripening

The aim of this study was to follow expression of ethylene signalling genes during storage and ripening of kiwifruit at low temperature. Kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) were stored at 0 °C for 12 weeks, followed by 6 d of shelf-life at 20 °C. Fruit ripened and softened slowly during storage at 0 °C, and no ethylene was detectable at the end of storage or during shelf-life. Five ethylene receptor genes, two CTR1-like genes and four EIN3-like genes showed different changes in expression during low temperature storage. Those genes showing altered expression could be divided into three groups: AdERS1a, AdETR2, AdETR3, AdCTR1 and four EIN3-like genes were up-regulated, while AdERS1b and AdETR1 were suppressed, and AdCTR2 was largely unchanged. On transfer to 20 °C shelf-life, most genes showed no substantial change, except for AdETR3 which was suppressed and AdETR1 and AdERS1b which were up-regulated. These gene expression patterns are indicative of specific and differential gene responses to low temperature during kiwifruit ripening.