Abstract
In this study, we aimed to identify differentially accumulated proteins (DAPs) involved in PEG mock osmotic stress, cadmium (Cd2+) stress, and their combined stress responses in Brachypodium distachyon seedling roots. The results showed that combined PEG and Cd2+ stresses had more significant effects on Brachypodium seedling root growth, physiological traits, and ultrastructures when compared with each individual stress. Totally, 106 DAPs were identified that are responsive to individual and combined stresses in roots. These DAPs were mainly involved in energy metabolism, detoxification and stress defense and protein metabolism. Principal component analysis revealed that DAPs from Cd2+ and combined stress treatments were grouped closer than those from osmotic stress treatment, indicating that Cd2+ and combined stresses had more severe influences on the root proteome than osmotic stress alone. Protein–protein interaction analyses highlighted a 14-3-3 centered sub-network that synergistically responded to osmotic and Cd2+ stresses and their combined stresses. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of 14 key DAP genes revealed that most genes showed consistency between transcriptional and translational expression patterns. A putative pathway of proteome metabolic changes in Brachypodium seedling roots under different stresses was proposed, which revealed a complicated synergetic responsive network of plant roots to adverse environments.
Highlights
Cadmium (Cd) and drought are two common abiotic stresses, in places contaminated with heavy metals
The results showed that plant height, relative water content, and main root length were significantly reduced under the three stresses, under the combined stresses, whereas proline, malondialdehyde (MDA), soluble sugar, and betaine contents of B. distachyon accession 21 (Bd21) seedling roots were significantly increased, after 4 days of the combined stress treatment
We identified a considerable number of differentially accumulated proteins (DAPs) in response to polyethylene glycol (PEG), Cd2+, and their combined stresses in Bd21 seedling roots, which participated in wide metabolic processes
Summary
Cadmium (Cd) and drought are two common abiotic stresses, in places contaminated with heavy metals. Numerous proteomic studies of osmotic stress and heavy metal stress in different plant species have been performed due to the rapid advances in genomics, including Brassica juncea[23], rice[2,24], poplar[25], Arabidopsis[26,27], wheat[28,29,30], and soybean[31,32]. Most of these studies only involved a single stress treatment, and few are concerned with the underlying molecular mechanisms of plant responses to a combination of different abiotic stresses. It is crucial to realize the synergistic response mechanisms of plants suffering from multiple abiotic stresses, under combined osmotic and heavy metal stresses
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