Abstract
Wild jujube (Ziziphus acidojujuba Mill.) is highly tolerant to alkaline, saline and drought stress; however, no studies have performed transcriptome profiling to study the response of wild jujube to these and other abiotic stresses. In this study, we examined the tolerance of wild jujube to NaHCO3-NaOH solution and analyzed gene expression profiles in response to alkaline stress. Physiological experiments revealed that H2O2 content in leaves increased significantly and root activity decreased quickly during alkaline of pH 9.5 treatment. For transcriptome analysis, wild jujube plants grown hydroponically were treated with NaHCO3-NaOH solution for 0, 1, and 12 h and six transcriptomes from roots were built. In total, 32,758 genes were generated, and 3,604 differentially expressed genes (DEGs) were identified. After 1 h, 853 genes showed significantly different expression between control and treated plants; after 12 h, expression of 2,856 genes was significantly different. The expression pattern of nine genes was validated by quantitative real-time PCR. After gene annotation and gene ontology enrichment analysis, the genes encoding transcriptional factors, serine/threonine-protein kinases, heat shock proteins, cysteine-like kinases, calmodulin-like proteins, and reactive oxygen species (ROS) scavengers were found to be closely involved in alkaline stress response. These results will provide useful insights for elucidating the mechanisms underlying alkaline tolerance in wild jujube.
Highlights
Salinity and alkalinity are the two main environmental factors that inhibit the growth and development of crops, reducing agricultural production, and, in severe conditions, resulting in plant death
We examined whether the alkaline stress causes oxidative stress in wild jujube seedlings by quantifying the content of H2O2
We identified 39 unique Heat shock proteins (HSP) including HSP70s and small HSPs, which were differentially expressed under alkaline stress (Fig 5 and S9 Table)
Summary
Salinity and alkalinity are the two main environmental factors that inhibit the growth and development of crops, reducing agricultural production, and, in severe conditions, resulting in plant death. An estimated 950 million hectares of the global land surface consists of saline-alkaline soil [1]. Previous studies have demonstrated that saline and alkaline stresses have different impacts on plant [2]. Saline soils, which are generally dominated by the cation Na+, and the anions Cl− and SO42- result in osmotic stress and ion injury. Alkaline stress (NaHCO3 and Na2CO3), involves multiple factors, including osmotic stress and ion injury, and the elevated soil pH (pH > 8.5) is much more destructive to plants than neutral salts [3].
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