Evolution analysis of Dof transcription factor family and their expression in response to multiple abiotic stresses in Malus domestica

As a family of transcription factors, DNA binding with one figure (Dof) proteins play important roles in various biological processes in plants. Here, a total of 60 putative apple (Malus domestica) Dof genes (MdDof) were identified and mapped to different chromosomes. Chromosomal distribution and synteny analysis indicated that the expansion of the MdDof genes came primarily from segmental and duplication events, and from whole genome duplication, which lead to more Dof members in apples than in other plants. All 60 MdDof genes were classified into thirteen groups, according to multiple sequence alignment and the phylogenetic tree constructed of Dof genes from apple, peach (Prunus persica), Arabidopsis and rice. Within each group, the members shared a similar exon/intron and motif compositions, although the sizes of the MdDof genes and encoding proteins were quite different. Several Dof genes from the apple and peach were identified to be homologues based on their close synteny relationship, which suggested that these genes bear similar functions. Half of the MdDof genes were randomly selected to determine their responses to different stresses. The majority of MdDof genes were quite sensitive to PEG, NaCl, cold and exogenous ABA treatment. Our results suggested that MdDof family members may play important roles in plant tolerance to abiotic stress.