Molecular cloning and characterization of genes related to the ethylene signal transduction pathway in pomegranate (Punica granatum L.) under different temperature treatments

Low temperature storage is a common method for storing pomegranates post-harvest; however, unsuitable low temperatures can cause fruit chilling injuries, the molecular mechanism of which is as yet unclear. Ethylene is a major factor affecting the post-harvest storage quality of pomegranates, and functions mainly through the ethylene signal transduction pathway. ERF1, ERF2 and ETR are key genes in the ethylene signal transduction pathway. Here, we used RACE and homologous cloning techniques to obtain PgERF1 (KU058889), PgERF2 (KU058890) and PgETR (KU058891) from Punica granatum cv. Yushizi. Sequence alignment and functional domain analysis revealed that both PgERF1 and PgERF2 contained a DNA-binding-site at the 120th to 177th amino acids of the N-terminus, which is a typical AP2/ERF center structure domain. Analysis of changes in expression of PgERF1, PgERF2 and PgETR following storage for different lengths of time (0, 14, 28, 42 and 56 days) at different temperatures (0 degrees C, 5 degrees C, 10 degrees C and 15 degrees C) revealed that the expression levels of PgERF1 and PgERF2 had a significant positive correlation. At the same time, the expression of both PgERF1 and PgERF2 increased continuously with time when seeds were stored at 0 degrees C. However, there was no obvious linear relationship between time stored and the levels of expression of PgETR. Therefore, we inferred that at 0 degrees C, the ethylene signal transduction pathway might play an important role in fruit chilling injuries during post-harvest storage.