Quercus suber Roots Activate Antioxidant and Membrane Protective Processes in Response to High Salinity

Halophyte Nitraria billardieri CIPK25 mitigates salinity-induced cell damage by alleviating H2O2 accumulation

The plant-specific module of calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) play a crucial role in plant adaptation to different biotic and abiotic stresses in various plant species. Despite the importance of the CBL-CIPK module in regulating plant salt tolerance, few halophyte CIPK orthologs have been studied. We identified NbCIPK25 in the halophyte Nitraria billardieri as a salt-responsive gene that may improve salt tolerance in glycophytes. Sequence analyses indicated that NbCIPK25 is a typical CIPK family member with a conserved NAF motif, which contains the amino acids: asparagine, alanine, and phenylalanine. NbCIPK25 overexpression in salt-stressed transgenic Arabidopsis seedlings resulted in enhanced tolerance to salinity, a higher survival rate, longer newly grown roots, more root meristem cells, and less damaged root cells in comparison to wild-type (WT) plants. H2O2 accumulation and malondialdehyde (MDA) content were both deceased in NbCIPK25-transgenic plants under salt treatment. Furthermore, their proline content, an important factor for scavenging reactive oxygen species, accumulated at a significantly higher level. In concordance, the transcription of genes related to proline accumulation was positively regulated in transgenic plants under salt condition. Finally, we observed a stronger auxin response in salt-treated transgenic roots. These results provide evidence for NbCIPK25 improving salt tolerance by mediating scavenging of reactive oxygen species, thereby protecting cells from oxidation and maintaining plant development under salt stress. These findings suggest the potential application of salt-responsive NbCIPK25 for cultivating glycophytes with a higher salt tolerance through genetic engineering.

Strategies and prospects for biostimulants to alleviate abiotic stress in plants

Global climate change-induced abiotic stresses (e.g., drought, salinity, extreme temperatures, heavy metals, and UV radiation) have destabilized the fragile agroecosystems and impaired plant performance and thereby reducing crop productivity and quality. Biostimulants, as a promising and eco-friendly approach, are widely used to address environmental concerns and fulfill the need for developing sustainable/modern agriculture. Current knowledge revealed that plant and animal derived stimulants (e.g., seaweeds and phytoextracts, humic substances, and protein hydrolysate) as well as microbial stimulants (e.g., plant beneficial bacteria or fungi) have great potential to elicit plant tolerance to various abiotic stresses and thus enhancing plant growth and performance-related parameters (such as root growth/diameter, flowering, nutrient use efficiency/translocation, soil water holding capacity, and microbial activity). However, to successfully implement biostimulant-based agriculture in the field under changing climate, the understanding of agricultural functions and action mechanism of biostimulants coping with various abiotic stresses at physicochemical, metabolic, and molecular levels is needed. Therefore, this review attempts to unravel the underlying mechanisms of action mediated by diverse biostimulants in relation to abiotic stress alleviation as well as to discuss the current challenges in their commercialization and implementation in agriculture under changing climate conditions.