Salt tolerance in soybean WF-7 is partially regulated by ABA and ROS signaling and involves withholding toxic Cl− ions from aerial tissues

Abstract

Salt tolerance in plants is a complex trait involving multiple mechanisms. Understanding these mechanisms and their regulation will assist in developing novel strategies to engineer salt-tolerant crops. In the current study, we investigated salt-tolerant mechanisms in soybean (Glycine max) cultivar WF-7 in comparison to salt-sensitive Union. In vivo and in vitro salt assays demonstrated the salt tolerance of WF-7 at the seedling stage and during germination. After a 10-day 200 mM NaCl treatment, chlorophyll content in Union was reduced by 50 % compared to a 17 % reduction in WF-7. WF-7 was also less affected by abscisic acid (ABA) and NaCl during germination than Union. Upon ABA and NaCl treatment, the ABA-responsive genes SCOF1, ASN1, bZIP44, and AAPK1 are differentially expressed in WF-7 and Union seedlings. These results suggest that salt tolerance in WF-7 is in part regulated through an ABA-dependent pathway. In addition, following a 4-day 200 mM NaCl treatment, WF-7 produced more H₂O₂ than Union indicating the involvement of reactive oxygen species (ROS) in regulating salt tolerance in WF-7. Yet another mechanism WF-7 employs is withholding toxic chloride (Cl⁻) ions from aerial tissues. Following 200 mM NaCl treatment, Cl⁻ accumulation was mostly localized to the roots of WF-7. In contrast, most of the Cl⁻ in Union was transported into the stems and leaves. Taken together, our results demonstrated a role of ABA and ROS in regulating salt tolerance in WF-7, and the critical role of Cl⁻ in NaCl-induced mortality in soybean. Key message Withholding toxic Cl⁻ ions from leaves and, to a lesser extent, stems, confers salt tolerance to soybean WF-7. In addition, ABA and ROS may be involved in salt-stress signal transduction.

Reactive oxygen species, abscisic acid and ethylene interact to regulate sunflower seed germination

“…), and ABA‐mediated response to salt stress or drought is related to ROS production (Cruz de Carvalho ; Ren et al . ). In contrast, exogenous ABA reduced ROS accumulation in wheat leaves by stimulating antioxidant enzyme activities (Du et al .…”

Salinity Tolerance of Super-Nodulating Soybean Genotype En-b0-1

“…3). Therefore, the salinity tolerance in these soybean cultivars was associated with tolerance to both Na and Cl, although several previous studies had suggested that salt-induced inhibition of growth was more closely associated with Cl than Na contents in aboveground plant parts (Abel and Mackenzie, 1964;Abel, 1969;Parker et al,1983;Yang and Blanchar, 1993;Valencia et al, 2008;Ren et al, 2012). In this respect, Dabuxilatu and Ikeda (2005) ascribed the greater toxicity of Cl to its allocation within the plant: Cl was stored in both vacuoles and apoplastic spaces in both leaves and roots, whereas Na was predominantly stored in vacuoles in roots.…”

Chloride on the Move

“…Other post-translational signals, in addition to ABA, that may regulate Clloading of the xylem include ROS, which was associated with Clexclusion in soybean [97], GABA and ATP, which have been shown to inhibit ALMT activity [68,98,99]. ATP also regulates CLC activity so may affect root storage capacity for Cl -, and therefore affect delivery of Clto the xylem [74,100].…”