A Moso Bamboo Drought-Induced 19 Protein, PeDi19-4, Enhanced Drought and Salt Tolerance in Plants via the ABA-Dependent Signaling Pathway

Adaptive responses of nitric oxide (NO) and its intricate dialogue with phytohormones during salinity stress

Nitric oxide (NO) is a gaseous free radical that acts as a messenger for various plant phenomena corresponding to photomorphogenesis, fertilisation, flowering, germination, growth, and productivity. Recent developments have suggested the critical role of NO in inducing adaptive responses in plants during salinity. NO minimises salinity-induced photosynthetic damage and improves plant-water relation, nutrient uptake, stomatal conductance, electron transport, and ROS and antioxidant metabolism. NO contributes active participation in ABA-mediated stomatal regulation. Similar crosstalk of NO with other phytohormones such as auxins (IAAs), gibberellins (GAs), cytokinins (CKs), ethylene (ET), salicylic acid (SA), strigolactones (SLs), and brassinosteroids (BRs) were also observed. Additionally, we discuss NO interaction with other gaseous signalling molecules such as reactive oxygen species (ROS) and reactive sulphur species (RSS). Conclusively, the present review traces critical events in NO-induced morpho-physiological adjustments under salt stress and discusses how such modulations upgrade plant resilience.

Transcription Factor SlAREB1 Is Involved in the Antioxidant Regulation under Saline–Alkaline Stress in Tomato

Basic leucine zipper (bZIP) transcription factors of the ABA-responsive element binding factor/ABA-responsive element binding proteins (ABF/AREB) subfamily have been implicated in abscisic acid (ABA) and abiotic stress responses in plants. However, the specific function of ABF/AREB transcription factors under saline–alkaline stress is unclear. Here, we identified four ABF/AREB transcription factors in tomato and found that SlAREB1 strongly responded to both ABA and saline–alkaline stress. To further explore the function of SlAREB1 under saline–alkaline stress, SlAREB1-overexpressing lines were constructed. Compared with wild-type plants, SlAREB1-overexpressing transgenic tomato plants showed reduced malondialdehyde content, increased the relative water content, and alleviated the degradation of chlorophyll under saline–alkaline stress. Importantly, SlAREB1 directly physically interacted with SlMn-SOD, which improved the activity of antioxidant enzymes and increased the scavenging of excess reactive oxygen species. Overall, the overexpression of SlAREB1 increased the antioxidant capacity of the transgenic tomato under saline–alkaline stress.

PeSNAC-1 a NAC transcription factor from moso bamboo (Phyllostachys edulis) confers tolerance to salinity and drought stress in transgenic rice

NAC (NAM, AFAT and CUC) proteins play necessary roles in plant response to environmental stresses. However, the functional roles of NAC genes in moso bamboo (Phyllostachys edulis), an essential economic perennial woody bamboo species, are not well documented. In this study, we retrieved 152 PeNAC genes from the moso bamboo V2 genome, and PeSNAC-1 was isolated and functionally characterized. PeSNAC-1 was localized in the nucleus and had no transactivation activity in yeast. PeSNAC-1 extremely expressed in rhizome and young roots (0.1 and 0.5 cm) and was significantly induced by drought and salt treatments but repressed by abscisic acid (ABA), methyl jasmonate and high temperature (42 °C) in moso bamboo. Under water shortage and salinity conditions, survival ratios, Fv/Fm values, physiological indexes such as activities of superoxide dismutase, peroxidase and catalase and contents of malondialdehyde, H2O2 and proline were significantly higher in transgenic rice than the wild type, which suggests enhanced tolerance to drought and salt stress in PeSANC-1 overexpressed plants. Transcript levels of Na+/H+ antiporter and Na+ transporter genes (OsSOS1, OsNHX1 and OsHKT1;5), ABA signaling and biosynthesis genes (OsABI2, OsRAB16, OsPP2C68, OsLEA3-1, OsLEA3, OsNCED3, OsNCED4 and OsNCED5) and ABA-independent genes (OsDREB1A, OsDREB1B and OsDREB2A) were substantially higher in transgenic as compared with the wild type. Moreover, protein interaction analysis revealed that PeSNAC-1 could interact with stress responsive PeSNAC-2/4 and PeNAP-1/4/5 in both yeast and plant cells, which indicates a synergistic effect of those proteins in regulating the moso bamboo stress response. Our data demonstrate that PeSNAC-1 likely improved salt and drought stress tolerance via modulating gene regulation in both ABA-dependent and independent signaling pathways in transgenic rice. In addition, PeSNAC-1 functions as an important positive stress regulator in moso bamboo, participating in PeSNAC-1 and PeSNAC-2/4 or PeSNAC-1 and PeNAP-1/4/5 interaction networks.

Exogenous Abscisic Acid Alleviates Harmful Effect of Salt and Alkali Stresses on Wheat Seedlings

Exogenous hormones play an important role in plant growth regulation and stress tolerance. However, little is known about the effect of exogenous abscisic acid (ABA) on wheat seedlings under salt and alkali stresses. Here, a pot experiment of saline and alkaline stresses (0 and 100 mmol/L) in which ABA water solution (0, 50 and 100 μmol/L) was sprayed on wheat seedlings was conducted to study the alleviative effectiveness of ABA on salt and alkali stresses. After spraying ABA (50 μmol·L-1), shoot biomass increased 19.0% and 26.7%, respectively. The Na+ content in shoots reduced from 15-fold and 61.5-fold to 10-fold and 37.3-fold in salt and alkali stresses, compared to controls. In addition, proline and organic acid synthesis in shoots also reduced significantly, but the soluble sugar content increased under alkali stress. A high concentration of ABA (100 μmol·L-1) had no significant effects on biomass and ion content in wheat seedlings under both stresses. In conclusion, foliar application of ABA with moderate concentration could effectively accelerate shoot growth of salt-induced wheat seedlings by adjusting the levels of ions and organic solutes.