Abstract
Plant 14-3-3 proteins are involved in diverse biological processes, but for the model monocotyledonous species, Brachypodium distachyon, their roles in abiotic stress tolerance are not well understood. In this study, a total of eight Bd14-3-3 genes were identified from B. distachyon and these were designated respectively as BdGF14a–BdGF14g. The qRT-PCR analyses of 3-month-old plants of B. distachyon showed that these genes were all expressed in the stems, leaves, and spikelets. By contrast, most of the plants had relatively lower transcriptional levels in their roots, except for the BdGF14g gene. The different expression profiles of the Bd14-3-3s under various stress treatments, and the diverse interaction patterns between Bd14-3-3s and BdAREB/ABFs, suggested that these gene products probably had a range of functions in the stress responses. The NaCl-induced Bd14-3-3 gene, BdGF14d, was selected for overexpression in tobacco. BdGF14d was found to be localized throughout the cell and it conferred enhanced tolerance to salt in the transgenic plants. Lowered contents of malondialdehyde, H2O2, and Na+, and lower relative electronic conductance (Rec%), yet greater activities of catalase and peroxidase, were observed in the overexpressing plants. Higher photosynthetic rate, transpiration rate, stomatal conductance, and water use efficiency were measured in the transgenic lines. Following abscisic acid (ABA) or NaCl treatment, stomatal aperture in leaves of the BdGF14d-overexpression plants was significantly lower than in leaves of the wild type (WT) controls. The stress-related marker genes involved in the ABA signaling pathway, the reactive oxygen species (ROS)-scavenging system, and the ion transporters were all up-regulated in the BdGF14d-overexpressing plants as compared with WT. Taken together, these results demonstrate that the Bd14-3-3 genes play important roles in abiotic stress tolerance. The ABA signaling pathway, the ROS-scavenging system, and ion transporters were all involved in enhancing the tolerance to salt stress in the BdGF14d-overexpression plants.
Highlights
Many processes in the life cycles of plant require specific signal transduction to achieve vital biological functions
A total of eight Bd14-3-3 genes were identified from B. distachyon through the BLAST searches and the Pfam analyses; they were designated as BdGF14a, BdGF14b, BdGF14c1, BdGF14c2, BdGF14d, BdGF14e, BdGF14f, and BdGF14g, respectively, based on the nomenclature in rice (Chen et al, 2006) and their chromosomal location, which was inconsistent with previous report (Cao et al, 2016) that we identified an alternative splicing in BdGF14c
The results indicated that the Bd14-3-3 family members in B. distachyon were highly conserved during evolution (Figure 1A), in accordance with their highly similar amino acid alignment (Figure 1C)
Summary
Many processes in the life cycles of plant require specific signal transduction to achieve vital biological functions. A common way to transfer such information is via the interaction between proteins, as modified by reversible phosphorylation (Ferl, 2004; Chevalier et al, 2009). Since reversible phosphorylation of a protein alone is insufficient to complete the interaction directly, 14-3-3s, as crucial adaptor proteins are of great importance in plants because they bind phosphorylated peptides in the regulation of a diversity of processes (Denison et al, 2011), notably primary metabolism (Comparot et al, 2003; Diaz et al, 2011) and light (Sullivan et al, 2009; Taoka et al, 2011) and hormone signaling pathways (Ishida et al, 2004; Schoonheim et al, 2007; Gokirmak et al, 2010; Wang H. et al, 2011). The structural characteristics of these 14-3-3 proteins equip them for the regulation of various environmental signaling pathways, such as those related to drought, high salinity, and extreme temperatures
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