Potential Role of <i>WIP</i> Family Genes in Drought Stress Response in <i>Rubus idaeus</i>

<i>Rubus idaeus</i> is one of the primary cultivated species of raspberries, renowned for its appealing color, distinctive flavor and numerous health benefits. WIP proteins, which contain three conserved amino acids (W: Tryptophan, I: Isoleucine, P: Proline) and four zinc finger motifs in a highly conserved C-terminal region, are members of the A1d subgroup of C2H2 zinc finger proteins. Drought is one of the main limiting factors of plant growth and development, which restricts the cultivation and utilization of raspberry in northwest China. In this study, to obtain candidate genes for drought resistance, we identified key related genes, <i>RiWIPs</i>, from <i>R. idaeus</i> and analyzed their bioinformation and tissue stress response expression to drought. We found that there are three <i>RiWIPs</i> in <i>R. idaeus</i> and they are located on chromosomes 3, 4 and 6 of <i>R. idaeus</i>, respectively. The open reading frames (ORFs) of the <i>RiWIPs</i> ranged from 870 to 1056 bp in length, encoding 289 to 372 amino acid residues. The proteins were highly conserved and feature diverse conserved motifs. The promoters of the <i>RiWIPs</i> contained abundant <i>cis</i>-elements related to growth, development and stress response. Tissue-specific expression analysis revealed that the <i>RiWIPs</i> were expressed in the leaves, stems and roots of both drought-susceptible and drought-tolerant cultivars, except for <i>RiWIP2</i>, which was only expressed in the roots of the drought-tolerant one. Under drought stress, the transcriptional activity of the <i>RiWIPs</i> was increased to different degrees with specificity in the leaves, stems and roots. Our study demonstrated the role of <i>WIP</i> genes in raspberry drought response and provided a marker gene, <i>RiWIP2</i>, for drought resistance and candidate genes for subsequent drought-resistant breeding of <i>R. idaeus</i>.