Overexpression of AtSTO1 leads to improved salt tolerance in Populus tremula × P. alba

Combating Salinity Through Natural Plant Extracts Based Biostimulants: A Review

Enhanced crop growth and yield are the recurring concerns in agricultural field, considering the soaring world population and climate change. Abiotic stresses are one of the major limiting factors for constraining crop production, for several economically important horticultural crops, and contribute to almost 70% of yield gap. Salt stress is one of these unsought abiotic stresses that has become a consistent problem in agriculture over the past few years. Salinity further induces ionic, osmotic, and oxidative stress that result in various metabolic perturbations (including the generation of reactive oxygen, carbonyl, and nitrogen species), reduction in water potential (ψw), distorted membrane potential, membrane injury, altered rates of photosynthesis, leaf senescence, and reduced nitrogen assimilation, among others); thereby provoking a drastic reduction in crop growth and yield. One of the strategies to mitigate salt stress is the use of natural plant extracts (PEs) instead of chemical fertilizers, thus limiting water, soil, and environmental pollution. PEs mainly consist of seeds, roots, shoots, fruits, flowers, and leaves concentrates employed either individually or in mixtures. Since PEs are usually rich in bioactive compounds (e.g., carotenoids, flavonoids, phenolics, etc.), therefore they are effective in regulating redox metabolism, thereby promoting plant growth and yield. However, various factors like plant growth stage, doses applied, application method, soil, and environmental conditions may greatly influence their impact on plants. PEs have been reported to enhance salt tolerance in plants primarily through modulation of signaling signatures and pathways (e.g., Na+, ANNA4, GIPC, SOS3, and SCaBP8 Ca2+ sensors, etc.), and regulation of redox machinery [e.g., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), non-specific peroxidase (POX), glutathione peroxidase (GPX), peroxiredoxin (Prx), ascorbic acid (AsA), glutathione (GSH), α-tocopherol, etc.]. The current study highlights the role of PEs in terms of their sources, methods of preparation, and mode of action with subsequent physiological changes induced in plants against salinity. However, an explicit mode of action of PEs remains nebulous, which might be explicated utilizing transcriptomics, proteomics, metabolomics, and bioinformatics approaches. Being ecological and economical, PEs might pave the way for ensuring the food security in this challenging era of climate change.

Impact of Nanomaterials on the Regulation of Gene Expression and Metabolomics of Plants under Salt Stress

Plant salinity resistance results from a combination of responses at the physiological, molecular, cellular, and metabolic levels. This article focuses on plant stress tolerance mechanisms for controlling ion homeostasis, stress signaling, hormone metabolism, anti-oxidative enzymes, and osmotic balance after nanoparticle applications. Nanoparticles are used as an emerging tool to stimulate specific biochemical reactions related to plant ecophysiological output because of their small size, increased surface area and absorption rate, efficient catalysis of reactions, and adequate reactive sites. Regulated ecophysiological control in saline environments could play a crucial role in plant growth promotion and survival of plants under suboptimal conditions. Plant biologists are seeking to develop a broad profile of genes and proteins that contribute to plant salt resistance. These plant metabolic profiles can be developed due to advancements in genomic, proteomic, metabolomic, and transcriptomic techniques. In order to quantify plant stress responses, transmembrane ion transport, sensors and receptors in signaling transduction, and metabolites involved in the energy supply require thorough study. In addition, more research is needed on the plant salinity stress response based on molecular interactions in response to nanoparticle treatment. The application of nanoparticles as an aspect of genetic engineering for the generation of salt-tolerant plants is a promising area of research. This review article addresses the use of nanoparticles in plant breeding and genetic engineering techniques to develop salt-tolerant crops.

Progress in Understanding the Physiological and Molecular Responses of Populus to Salt Stress

Salt stress (SS) has become an important factor limiting afforestation programs. Because of their salt tolerance and fully sequenced genomes, poplars (Populus spp.) are used as model species to study SS mechanisms in trees. Here, we review recent insights into the physiological and molecular responses of Populus to SS, including ion homeostasis and signaling pathways, such as the salt overly sensitive (SOS) and reactive oxygen species (ROS) pathways. We summarize the genes that can be targeted for the genetic improvement of salt tolerance and propose future research areas.

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

Lignin is an abundant biopolymer with a high carbon content and high aromaticity. Despite its potential as a raw material for the fuel and chemical industries, lignin remains the most poorly utilised of the lignocellulosic biopolymers. Effective valorisation of lignin requires careful fine-tuning of multiple "upstream" (i.e., lignin bioengineering, lignin isolation and "early-stage catalytic conversion of lignin") and "downstream" (i.e., lignin depolymerisation and upgrading) process stages, demanding input and understanding from a broad array of scientific disciplines. This review provides a "beginning-to-end" analysis of the recent advances reported in lignin valorisation. Particular emphasis is placed on the improved understanding of lignin's biosynthesis and structure, differences in structure and chemical bonding between native and technical lignins, emerging catalytic valorisation strategies, and the relationships between lignin structure and catalyst performance.