[Identification and functional analysis of the transcriptional factor GeERF4B-1 in Gelsemium elegans]

Gelsemium elegans, a vine plant of Loganiaceae, has both medicinal and forage values. However, it is susceptible to low temperatures during growth. Exploring low temperature response genes is of great significance for cold resistance breeding of G. elegans. Ethylene response factors (ERFs) are the transcription factors of the AP2/ERF superfamily and play a crucial role in plant stress response. In this study, based on the unigene GeERF involved in the response to low temperature stress in the transcriptome of G. elegans, a full-length cDNA sequence of the transcription factor GeERF4B-1 was cloned from the leaves of G. elegans by reverse transcription-polymerase chain reaction (RT-PCR). Bioinformatics analysis showed that GeERF4B-1 had an open reading frame of 759 bp, encoding a protein composed of 252 amino acid residues and with a relative molecular weight of 27 kDa. The deduced protein was predicted to be an unstable, alkaline, and hydrophilic protein. The phylogenetic tree showed that GeERF4B-1 was in the same clade as the B-4 subfamily of the ERF family. The results of the subcellular localization experiment revealed that GeERF4B-1 was located in the nucleus. Real time quantitative PCR (RT-qPCR) analysis indicated that GeERF4B-1 was expressed in the root, stem, and leaf of G. elegans, with the highest expression level in the root. Compared with the control, the treatments with a low temperature (4 ℃), methyl jasmonate (MeJA), and abscisic acid (ABA) up-regulated the expression level of GeERF4B-1, which reached the peak at 24-48 h. This result revealed that GeERF4B-1 actively responded to low temperature, MeJA, and ABA stresses. However, both sodium chloride (NaCl) and drought treatments down-regulated the expression of GeERF4B-1. In addition, a prokaryotic expression vector of GeERF4B-1 was constructed, and a fusion protein of approximately 52 kDa was yielded after induced expression. The results of the plate stress assay showed that compared with the control, the prokaryotic strain expressing GeERF4B-1 demonstrated enhanced tolerance to low temperatures and sensitivity to salt and mannitol stresses. This study provides theoretical references and potential genetic resources for breeding G. elegans varieties with stress resistance.