The Mechanism Of ERF Transcription Factors In Regulating Chilling Injury Of Cucumber Fruit

Low temperature storage is an effective postharvest practice commonly used to reduce postharvest deteriation of fruits and vegetables during the preservation and transporation. However, fruits and vegetables originated from tropical and subtropical regions are prone to chilling injury(CI) when exposed to improper cold temperatures. Cucumber is a typical cold-sensitive fruit and CI symptoms appear when the fruit are stored at temperatures below 10?. CI symptoms of cucumber fruit include surface pitting, dark watery patch and increased susceptibility to decay, thereby resulting in reduced commercial value. Ethylene responsive factor(ERF) is a kind of plant-specific transcription factors which plays an essential role in biotic and abiotic stresses, but its involvement in CI of cucumber fruit as well as its transcriptional regulatory mechanism have received less attention. In this study, we compared the transcriptomes of cucumber fruit(Cucumis sativus L. cv. ‘Jingdong') with or without CI to find out some ERF transcription factors which were associated with CI of cucumber fruit. Moreover, the possible interactions between cucumber ERFs and histone deacetylases(HDACs) were also analyzed, in order to elucidate the regulatory mechanism of ERFs involved in CI of cucumber fruit. The main results are as follows:1. Cold acclimation treatment which held the cucumber fruit at 15?for two days can effectively reduce the CI of cucumber fruit at 8?, as evidenced by the changes of CI index, weight loss, and chrolophyll content.2. RNA-Seq analysis showed that there are 337 genes differentially expressed in cucumber fruits with and without CI. Among them, a total of 29 ERF genes were found and named Cs ERF1-29. In addition, 21 HDAC genes in cucumbers from NCBI were selected and designated as Cs HDA1-21.3. q RT-PCR analysis reavealed that Cs ERFs and Cs HDAs transcripts displayed differential expression pattern during the progression of CI. In particular, the expression levels of Cs ERF1/14/17/18/24/28/29 and Cs HDA3/7/8/17/18/21 were upregulated, whereas those of Cs ERF4/7/8/16/27 were dowregulated. It is assumed that these genes may be associated with CI in cucumber friuts.4. Based on their expression pattern, we chose Cs ERF4/18/27/29 and Cs HDA3/7/8/17/18/21 to test the possible interactions between Cs ERFs and Cs HDAs. Yeast two-hybrid(Y2H) assay and bimolecular fluorescence complementation(Bi FC) assay demonstrated that Cs ERF29 was able to interact with Cs HDA18. The biological function of this interaction in CI of cucumber fruit needs to be investigated further.