The continuously changing environment has led to devastating effects on the normal growth and development of plants. This necessitates the understanding of different components that can be involved in alleviating these effects. In the last two decades, nitric oxide (NO) has been largely focused on as a molecule whose endogenous production and exogenous supply lead to several molecular and physiological changes in plants under stressed conditions. Although its role as a signaling molecule in endogenous production has been largely discussed, its function in dealing with contemporary abiotic stress conditions on exogenous supply remains comparatively less explored. There is growing evidence that NO plays a critical role in many physiological processes; however, there is debate about the exact mechanism(s) through which NO lessens abiotic stress on external supply. In this review, we discuss the studies that were focused on observing the effect of exogenous NO on different abiotic stresses including heavy metal stress, element deficiency or toxicity stress, salt stress, drought stress, ultraviolet radiation stress, waterlogging stress, and chilling stress. Though the positive effects of endogenous NO have been discussed in brief in different sections, the focus of the review is to discuss the effects of exogenous NO on plant grown under abiotic stresses. Deciphering the underlying mechanism of exogenous NO treatment may open up new ideas that can suggest the successful application of NO in agricultural regions to reduce the damaging influences of different abiotic stresses.

Key message: PvMLP19 overexpression in Arabidopsis enhances proline accumulation, mitigates oxidative stress, improves water retention, delays germination, and stimulates root growth under drought and salt stress conditions. Climate change has exacerbated the frequency and severity of drought and salinity stress, posing significant risks to agricultural productivity and food security. As sessile organisms, plants have evolved regulatory mechanisms to adapt to these challenges. Common bean (Phaseolus vulgaris L.), an essential legume crop valued for its high nutritional value, is increasingly impacted by climate change-induced stressors. The PR10 protein family has been recognized as a potential contributor to enhancing plant resilience to abiotic and biotic stresses. This family, also known as Bet v1, is highly conserved and consists of diverse subfamilies, including major latex proteins (MLPs), which may contribute to stress tolerance through ligand-binding and regulation of stress-related pathways. This study aimed to investigate the functional role of PvMLP19 in stress tolerance using both in silico and experimental approaches. RNA-seq analysis revealed tissue-specific expression patterns of PR10s, with PvMLP19 showing notable induction under abiotic stress. Functional validation in transgenic Arabidopsis suggested that overexpression of PvMLP19 may improve drought tolerance. Transgenic plants exhibited increased proline accumulation, reduced oxidative stress, and higher relative water content under both drought and salinity stress conditions. Furthermore, PvMLP19 overexpression was associated with delayed seed germination but promoted root development under osmotic and salinity stress. The increased stress tolerance was linked to the upregulation of stress-inducible genes, suggesting a potential regulatory role of PvMLP19 in modulating stress-response pathways. These findings position PvMLP19 as a potential candidate for genetic improvement in crops, offering a promising strategy to mitigate the impacts of climate change and ensure sustainable agricultural productivity.

Anthocyanins are responsible for the coloration of common bean seeds, and their accumulation is positively correlated with the expression level of anthocyanin biosynthetic genes. The MBW (MYB-bHLH-WD40) complex is thought to regulate the expression of these genes, and MYB proteins, which are a key factor in activating anthocyanin pathway genes, have been identified in several plants. This study demonstrated gene structures, chromosomal placements, gene duplications of R2R3-MYBs, miRNAs associated with R2R3-MYBs, and the interaction of these genes with other flavonoid regulatory genes. qRT-PCR was used to investigate the role of specific R2R3-MYBs and flavonoid genes in common bean seed color development. As a result of a comprehensive analysis with the help of in silico tools, we identified 160 R2R3-MYB genes in the common bean genome. We divided these genes into 16 classes on the basis of their intron-exon and motif structures. Except for three, the rest of the common bean R2R3-MYB members were distributed to all chromosomes with different densities, primarily located on chromosomes 3 and 8. We identified a total of 44 duplicated gene pairs dispersed across 11 chromosomes and evolved under purifying selection (Ka/Ks < 1), 19 of which were derived from a whole-genome duplication. Our research uncovered 25 putative repressor PvMYB proteins that contain the EAR motif. Additionally, fifty different cis-regulatory elements regulated by light, stress, and hormone were identified. Within the genome of the common bean, we discovered a total of 36 microRNAs that target a total of 72 R2R3-MYB transcripts. The effect of 16 R2R3-MYB genes and 16 phenylpropanoid pathway genes, selected on the basis of their interaction in the protein-protein interaction map, playing role in the regulation of seed coat color development was evaluated using qRT-PCR in 5 different tissues at different developmental stages. The results revealed that these specific genes have different expression levels during different developmental periods, with higher levels in the pod filling and early pod stages than in the rest of the developmental periods. Furthermore, it was shown that PvTT8 (bHLH), PvTT2 (PvMYB42), PvMYB113, PvTTG1, and PvWD68 genes have effects on the regulation of seed coat color. The findings of this study, which is the first to use whole-genome analysis to identify and characterize the R2R3-MYB genes in common bean, may serve as a reference for future functional research in the legume.

Synergistic and antagonistic relationships between cytokinins and other plant growth regulators are important in response to changing environmental conditions. Our study aimed to determine the functions of SlHP2 and SlHP3 , two members of cytokinin signaling in tomato, in drought stress response using CRISPR/Cas9‐mediated mutagenesis. Ten distinct genome‐edited lines were generated via Agrobacterium tumefaciens ‐mediated gene transfer and confirmed through Sanger sequencing. Stress experiments were conducted with two of these lines ( slhp2,3‐10 and slhp2,3‐11 ), which harbored homozygous mutations in both genes. The responses of two lines carrying homozygous mutations in both genes under polyethylene glycol (PEG)‐induced stress were examined using morphological, physiological, biochemical, and molecular methods. The genome‐edited lines demonstrated enhanced water retention, reduced stomatal density, and less oxidative damage compared to the wild‐type plants under PEG‐induced stress. Moreover, the slhp2,3 double mutant plants exhibited improved root growth, showcasing their superior drought tolerance over wild‐type plants by accessing deeper water sources and maintaining hydration in water‐limited environments. To investigate the involvement of cytokinin signaling regulators and genes associated with stomatal formation and differentiation, the expression of genes ( Speechless [ SPCH ], FAMA , MUTE , TMM , HB25 , HB31 , RR6 , RR7 , and Solyc02g080860 ) was assessed. The results revealed that all regulators were downregulated, with SPCH , TMM , RR7 , and RR6 showing significant reductions under PEG‐induced stress. These results emphasize the promise of utilizing CRISPR/Cas9 to target cytokinin signaling pathways, enhancing drought tolerance in tomatoes through improvements in water retention and root growth, along with a reduction in stomatal density and malondialdehyde content.