Abstract
DNA-binding one zinc-finger (Dof) proteins constitute a family of transcription factors with a highly conserved Dof domain that contains a C2C2 zinc-finger motif. Although several studies have demonstrated that Dof proteins are involved in multiple plant processes, including development and stress resistance, the functions of these proteins in drought stress resistance are largely unknown. Here, we report the identification of the MdDof54 gene from apple and document its positive roles in apple drought resistance. After long-term drought stress, compared with nontransgenic plants, MdDof54 RNAi plants had significantly shorter heights and weaker root systems; the transgenic plants also had lower shoot and root hydraulic conductivity, as well as lower photosynthesis rates. By contrast, compared with nontransgenic plants, MdDof54-overexpressing plants had higher photosynthesis rates and shoot hydraulic conductivity under long-term drought stress. Moreover, compared with nontransgenic plants, MdDof54-overexpressing plants had higher survival percentages under short-term drought stress, whereas MdDof54 RNAi plants had lower survival percentages. MdDof54 RNAi plants showed significant downregulation of 99 genes and significant upregulation of 992 genes in response to drought, and 366 of these genes were responsive to drought. We used DAP-seq and ChIP-seq analyses to demonstrate that MdDof54 recognizes cis-elements that contain an AAAG motif. Taken together, our results provide new information on the functions of MdDof54 in plant drought stress resistance as well as resources for apple breeding aimed at the improvement of drought resistance.
Highlights
Drought stress is one of the most important limiting factors for global agricultural development because it can impair crop growth and production[1]
We found that MdDof[54] is significantly induced by polyethylene glycol (PEG) in Malus sieversii, which is extremely tolerant to drought stress[42]
Among the differentially expressed genes (DEGs), we identified a zinc-finger TF that was dramatically induced by drought[42]
Summary
Drought stress is one of the most important limiting factors for global agricultural development because it can impair crop growth and production[1]. Plants have evolved a series of responses to address the adverse effects of drought stress at the morphological, physiological, and molecular levels[2,3]. Plant morphological and physiological responses to drought stress have been thoroughly studied[3]; the molecular mechanisms underlying drought resistance are more elusive and complex. Transcriptional regulation plays a central role in the control of plant development and responses to abiotic stress, and transcription factors. One group of TFs whose members are involved in the plant stress response are TFs with zinc-finger-binding domains that bind to DNA to activate or suppress the transcription of downstream target genes[12]. Recent research suggests that zinc-finger TFs play important roles in plant development and stress tolerance[13,14,15,16,17,18,19]. Zinc-finger proteins are classified into several subgroups based on the number and location of cysteine (C) and/or histidine (H) residues: C2H2 (TFIIIA), C8 (steroid-thyroid receptor), C6 (GAL4), C3HC4 (RING finger), C2HC (retroviral nucleocapsid), C2HC5 (LIM domain), C2C2
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