| Zinc finger-containing glycine-rich RNA-binding protein (RZ) belongs to the subclass b in class IV of glycine-rich proteins (GRP) superfamily, which plays an important role in plant growth and development as well as in various stresses. In this study, a novel and full-length cDNA sequence of RZ gene in Malus prunifolia, named MpRZ1, was amplified by in silico cloning and RT-PCR methods based on four RZ transcript sequences from the transcriptome library of M. prunifolia under drought stress. The structural and functional characteristics of the deduced amino acid sequence of MpRZ1 gene was analyzed using bioinformatics methods, and a comparative analysis of MpRZ1 protein with predicted apple RZs homologous members was conducted. The expression pattern of MpRZ1 gene was conducted by quantitative RT-PCR technology. The cDNA sequence of MpRZ1 gene was 930 bp in length contained an intact open reading frame of 843 bp, encoding a polypeptide of 280 amino acid residues with a predicted molecular mass of 30.97 kDa and a pI of 9.37. N-terminal signal peptide and transmembrane topology were not found in MpRZ1 protein, which was probably located in the nucleus and an unstable alkaline hydrophilic protein containing 38 potential phosphorylation sites, 13 O-GlcNAc and 5 N-Glyc glycosylation sites. The secondary elements of MpRZ1 protein was mainly characterized by random curling and α-helice, accounting for up to 87.1%. The predicted MpRZ1 protein contains one conserved RNA-recognition motif (RRM) with five antiparallel β-strands and 2 α-helices arranged in β1α1β2β3α2β4β5 topology at the N-terminus, and a CCHC type zinc finger domain as well as a series of (GGX)n and (DRY/F)n repeats at the C-terminal glycine-rich region. Sequence alignment and phylogenetic analysis indicated that the predicted MpRZ1 protein shared higher sequence similarity and homology with Arabidopsis and rice RZ proteins, suggesting this MpRZ1 gene belongs to a homologous member of RZ genes family. Nine different MdRZ transcripts found in the apple genome uniformly encoded alkaline hydrophilic proteins, and this MpRZ1 protein had more than 96% homology with two MdRZ proteins encoded by MdP0000088428 and MdP0000272138 transcripts. Compared with those of the control condition, the expression level of RZ genes in leaves of M. prunifolia and M. hupehensis slowly increased at the beginning and then decreased during drought stress, and significantly upregulated at 9 days(p<0.05). The MpRZ1 gene was involved in the drought stress response process, which lays a foundation for the molecular mechanism of RZ genes in apple rootstocks. |