Although simultaneous drought and cold stress occurs, especially in northwestern and eastern regions of China, and is an important factor limiting agricultural productivity, there are few studies focusing on plant responses to a combination of drought and cold stress. Here, by partially overlapping drought and cold stresses, we characterized the acclimation of maize (Zea mays B73) to these two stresses using physiological measurements, as well as comparative transcriptomics combined with metabolomics and hormonal analyses during the stress treatments and recovery stages. The combined drought and cold stress and drought stress alone were accompanied by a decline in photosynthetic capacity and enhanced transcriptional response, and subsequent recovery of these following removal from stress, whereas cold stress alone was accompanied by irreversible damage to photosynthetic capacity and chloroplast structure. The stress combination induced transcription-associated metabolomic alterations, in which raffinose, trehalose-6-phosphate, and proline accumulated, and monosaccharide abundance increased. Concomitantly, the increased abscisic acid (ABA) content and upregulated ABA signaling pathway may have provided the transcriptional regulation for the metabolic changes. In a parallel experiment, ABA treatments prior to exposure of the plants to cold stress primed the plants to survive the cold stress, thus confirming a key role for the endogenous ABA activated by the drought pretreatment in acclimation of the plants to cold. We present a model showing that the plant response to the combined stress is multi-faceted and reveal an ABA-dependent maize acclimation mechanism to the stress combination.

Perennial grasses undergo compensatory growth after defoliation. Nitrate is the main nitrogen source for the growth of perennial ryegrass and plays a significant role in plant resistance to stress. The aim of the study was to understand the physiological mechanism of ryegrass in response to defoliation stress under different nitrate supplies and to explore possible ways to alleviate defoliation stress. We performed pot experiments where 12-week-old ryegrass plants grown in low (0.05 mM KNO₃) or moderate nitrate (5 mM KNO₃) conditions were defoliated and subsequently supplied with different concentrations of nitrate following defoliation treatments. During the regrowth stage, the regrowth rate, biomass, photosynthetic parameters, and the response of the antioxidant system to low or moderate nitrate supply of ryegrass were investigated. The results showed that moderate nitrate supply after defoliation increased the content of photosynthetic pigments in ryegrass and improved its photosynthetic efficiency. In addition, adding moderate nitrate after defoliation increased the activity of antioxidant enzymes and the accumulation of osmotic regulating substances, thereby enhancing plant resistance, effectively reducing the damage to plants caused by defoliation stress, and promoting plant regrowth, especially for plants grown in a low nitrate environment before defoliation. Therefore, this study showed that the addition of exogenous nitrate could counteract some of the adverse effects of defoliation stress on the growth and development of ryegrass.

Drought stress is a major constraint on the productivity of temperate forage grasses such as perennial ryegrass (Lolium perenne). While nitrogen management is widely employed in agronomic practice, its specific role in mediating drought adaptation strategies remains unclear. This study aimed to systematically characterize the response of perennial ryegrass to drought stress following low nitrogen pre-acclimation through integrated physiological and transcriptomic analyses during both stress and recovery phases. Our results demonstrated that drought severely impaired photosynthetic capacity and induced oxidative damage in non-acclimated plants, as evidenced by the significant reductions in net photosynthetic rate, stomatal conductance and PSII efficiency (Fv/Fm), alongside elevated malondialdehyde (MDA) levels and increased activities of key antioxidant enzymes (e.g., ascorbate peroxidase, peroxidase and catalase). In contrast, low nitrogen pre-acclimation effectively preserved photosynthetic performance under subsequent drought, mitigating declines in gas exchange parameters and maintaining PSII integrity. These pre-acclimated plants also exhibited reduced oxidative stress under drought and superior recovery capacity after rewatering. This enhanced drought tolerance was associated with fructan accumulation and tempered transcriptional responses. Low nitrogen pre-acclimation mitigated the drought-induced transcriptional upheaval, attenuated the activation of hormonal signaling pathways and MAPK cascades, significantly alleviated the downregulation of genes encoding photosynthetic apparatus, stabilized chlorophyll metabolism and optimized carbon-nitrogen balance. These findings reveal a nitrogen-mediated priming mechanism that enhances drought tolerance through integrated metabolic and transcriptional adjustments, providing new insights into the interaction between nutrient signaling and stress resistance, as well as potential strategies for enhancing plant tolerance under climate change.

Drought stress significantly impairs plants' growth and productivity. Festuca rubra, a perennial turfgrass, is valued for its strong drought tolerance. However, the integrated physiological and molecular mechanisms underlying this trait remain poorly understand. In this study, following 21 d of drought stress, systematic physiological and transcriptomic analyses were conducted on F. rubra. Compared with the well-watered controls, the plants under drought stress exhibited a significant decrease in key photosynthetic parameters, accompanied by a notable upregulation in antioxidant enzyme activities. Concurrently, these plants also showed an augmented accumulation of osmoregulatory substances, including proline and soluble sugars. Under drought stress, 25,063 differentially expressed genes (DEGs) were identified by transcriptome analysis, including AP2/ERF, NAC, and bHLH transcription factors. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment revealed the repression of photosynthesis concurrent with the activation of plant hormone and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, key genes involved in proline biosynthesis and peroxisome function were markedly upregulated, indicating enhanced osmotic adjustment and oxidative stress defense. These results clarify the coordinated drought response mechanisms in F. rubra and provide valuable genetic resources for improving drought tolerance in turfgrass and related crops.

Soil salinization seriously damages plant growth and productivity. Festuca rubra (F. rubra) is a perennial grass with ecological and economic value, showing significant salt tolerance. However, its potential physiological and molecular mechanisms remain not fully elucidated. To explore F. rubra's response to salt stress, this study treated plants with salt stress (1% NaCl solution, w/v). Physiological parameters (relative electrical conductivity, photosynthetic traits, antioxidant systems) and transcriptomic profiles were analyzed at the terminal stress stage. Salt-stressed plants accumulated significantly higher levels of osmolytes (soluble sugars and proline). Antioxidant defenses were activated, as evidenced by increased activities of key antioxidant enzymes and elevated malondialdehyde (MDA) content. Net photosynthetic rate markedly declined under salt stress. Transcriptomic analysis revealed that salt stress activated genes associated with antioxidant enzymes and phytohormone signaling (predominantly ABA). It also induced upregulation of genes involved in carbon metabolism and amino acid biosynthesis pathways. These results demonstrate that F. rubra coordinates osmotic adjustment, activates antioxidants, and regulates transcription (specifically through ABA signaling and metabolic reprogramming) to mitigate salt-induced damage. These insights offer potential strategies for enhancing salt stress tolerance in graminaceous crops.

Fusarium acuminatum is a major pathogenic fungus causing root rot in alfalfa (Medicago sativa). DNA polymerase theta is known to play a crucial role in repairing DNA double-strand breaks. However, its biological function in F. acuminatum remains unknown. In this study, the POLQ gene was deleted by homologous recombination using Agrobacterium tumefaciens-mediated transformation. Compared to the wild type (with the POLQ gene), the mutants (without the POLQ gene) showed significant phenotypic changes: they produced brown-yellow pigments instead of pink, slowed mycelial growth, and exhibited changes in macroconidia size and shape. The virulence of the mutants was greatly reduced, inducing only mild symptoms in alfalfa. In addition, FITC-WGA staining showed impaired spore germination and hyphal growth. These results suggest that POLQ is a key gene regulating growth and development of F. acuminatum, indicating that DNA repair may play an essential role in the pathogenicity of the pathogen in alfalfa. The POLQ gene could thus be a promising target for limiting F. acuminatum infections in alfalfa.