In silico and Expression Profile Analyses of the ERF Subfamily in Melon

Ethylene-responsive factors (ERFs) are a subfamily of the AP2/ERF superfamily and a group of plant-specific transcription factors involved in many plant growth and development regulatory processes. However, few information about the function of ERFs in melon. To identify ERFs that may play a role in the growth and development of melon, using bioinformatics, we investigated their physicochemical properties, subcellular localization, signal peptides, promoter elements, and chromosomal location. Eighty-three promoter elements were predicted at 1500 bp upstream of their related genes. The chromosomal results suggested 64 ERFs are distributed among 12 chromosomes. On the basis of a multiple sequence alignment, phylogenetic analysis was conducted for all the ERF proteins in melon, arabidopsis (Arabidopsis thaliana) and tomato. Nine distinct groups were identified, and melon ERFs occurred within eight clades. Furthermore, the expression profiles of the genes in different tissues were investigated using quantitative real-time PCR (qRT-PCR). The results showed that 63, 57, and 54 ERF genes were expressed in distinct vegetative organs, fruits at different days after pollination (DAP), and fruits during the respiratory climacteric, respectively. Among those genes, CmERFIII-1 which was a valuable gene for studying its function in melon exhibited the highest expression in different tissues. Another very interesting gene was CmERFIV-2, which was the only gene whose expression was the highest in root in all highly expressed genes. Furthermore, four genes from the fourth subset (CmERFIV-2, IV-3, IV-4 and IV-5) were highly expressed in fruits at different developmental stages. Together, these results will aid future functional analysis of these genes.