Cloning and analysis of DlERF23 gene in flower induction

Irregular flowering is a serious problem in longan production. Identifying the flower induction-related genes and analyzing their regulation mechanism is the key to solve this problem. The APETALA2/ethylene responsive factor (AP2/ERF) superfamily members are transcription factors (TFs) that regulate diverse developmental processes, including flowering time, and stress responses in plants. However, there is still no research about AP2/ERF involved in the regulation of longan flower induction. In the present study, a AP2/ERF TF member DlERF23 was cloned from longan (Dimocarpus longan). It has a typical AP2 domain with the coding sequence (CDS) of DlERF23 is 552 bp in length and encodes 184 amino acids. The molecular weight of DlERF23 protein was 20.41 kda and the theoretical isoelectric point (PI) was 7.69. The amino acid sequence of DlERF23 protein had the highest similarity with CsERF23 (XP_006478313.1) of Citrus sinensis and CcERF23 (XP_006441807.2) of Citrus clementina. The results of qRT-PCR showed that the relative expression level of DlERF23 gene in pericarp was higher, followed by stem, leave, flower and flower bud. Meanwhile, DlERF23 gene significant down-regulated in the early stage of flower induction in ‘Sijimi’ (SJ) longan and up-regulated in the late stage of flower induction in ‘Shixia’ (SX). The results of transient expression of Arabidopsis protoplasts showed that the fluorescence signal was mainly concentrated in the nucleus. Moreover, overexpression of DlERF23 in Arabidopsis promoted early flowering. These results provide useful information for revealing the biological roles of DlERF23 in longan and increase our understanding of the AP2/ERF superfamily members in fruit trees.