AtHSPR may function in salt-induced cell death and ER stress in Arabidopsis

Abstract

Salt stress is a harmful and global abiotic stress to plants and has an adverse effect on all physiological processes of plants. Recently, we cloned and identified a novel AtHSPR (Arabidopsis thaliana Heat Shock Protein Related), which encodes a nuclear-localized protein with ATPase activity, participates in salt and drought tolerance in Arabidopsis. Transcript profiling analysis revealed a differential expression of genes involved in accumulation of reactive oxygen species (ROS), abscisic acid (ABA) signaling, stress response and photosynthesis between athspr mutant and WT under salt stress. Here, we provide further analysis of the data showing the regulation of salt-induced cell death and endoplasmic reticulum (ER) stress response in Arabidopsis and propose a hypothetical model for the role of AtHSPR in the regulation of the salt tolerance in Arabidopsis.

Keywords: Arabidopsis thaliana; ER stress; RNA-Seq; cell death; heat shock protein related; salt stress.

Figure 1.

Disruption of AtHSPR induced cell death, H₂O₂ accumulation in the leaf tip, and up-regulated expression of genes involved in cell death and ER stress response under both normal and salt conditions. (A). Visible cell death in the leaf tip of athspr mutant. The DAB staining or Evan's Blue staining was used for assessing H₂O₂ accumulation or cell death in WT, athspr mutant, complementation (COM) and overexpression (OE) lines, respectively. (B-C). Hierarchical clustering of the cell death genes or ER stress genes in four different pair-wise comparisons, which include: WT-s/WT (NaCl-treated WT relative to WT), athspr/WT (athspr relative to WT), athspr-s/athspr (NaCl-treated athspr relative to athspr) and athspr-s/WT-s (NaCl-treated athspr relative to NaCl-treated WT). The bottom bar shows the color scale for regulation ratio (log₂) relative to the control samples. (D-F). The relative expression of senescence-associated genes SAG13 and ER stress chaperone genes BIP1 and CNX1 in WT, athspr mutant and OE seedlings in response to NaCl treatment by qRT-PCR. Plants were grown for 2 weeks, and then treated with medium containing 200 mM NaCl for different time points. Error bars show standard deviations from three independent RNA extractions. Statistical significance was determined by a Duncan's multiple range test; significant differences (P = 0.05) are indicated by different lower-case letters.

Figure 2.

Working model of AtHSPR in responses to salt stress in Arabidopsis. AtHSPR confers salt tolerance by enhancing antioxidant defense, modulating ABA-dependent stomatal closure and signal transduction, maintaining photosynthesis and Na⁺/K⁺ homeostasis, and alleviating salt-induced ER-stress.