Switchgrass is an important bioenergy crop valued for its biomass yield and abiotic tolerance. Alkali stress is a major abiotic stress that significantly impedes plant growth and yield due to high salinity and pH; however, the response mechanism of switchgrass to alkali stress remains limited. Here, we characterized PvARL1, an ARF-like gene, which was up-regulated in both the shoot and root tissues under alkali stress conditions. Overexpression of PvARL1 not only improved alkali tolerance but also promoted biomass yield with more tiller and higher plant height in switchgrass. Moreover, PvARL1 overexpression lines displayed higher capacities in the maintenance of water content and photosynthetic stability compared with the controls under alkali treatments. A significant reduction in the ratio of electrolyte leakage, MDA content, and reactive oxygen species (ROS) showed that PvARL1 plays a positive role in protecting cell membrane integrity. In addition, PvARL1 also negatively affected the K⁺ efflux or uptake in roots to alleviate ion toxicity under alkali treatments. Overall, our results suggest that PvARL1 functions as a positive regulator in plant growth as well as in the plant response to alkali stress, which could be used to improve switchgrass biomass yield and alkali tolerance genetically.

Background Pennisetum hybrid (Pennisetum glaucum x Pennisetum purpureum), a perennial forage grass of the Poaceae family, it has a well-developed root system, strong tillering ability, high biomass yield, and rich nutritional content, making it a premium forage grass. However, Pennisetum genera grasses are sensitive to low-temperature stress and lacks the ability to adapt to cold environments, severely limiting its cultivation in temperate and high-altitude regions. Results We identified 23 PgCBF genes, unevenly distributed across chromosomes 1 to 7. Physicochemical property analysis revealed that the amino acid count of PgCBF family members ranged from 187 to 324, with molecular weights between 19688.36 and 34271.70 Da and theoretical isoelectric points between 4.57 and 9.82. Promoter region analysis of PgCBF genes indicated the presence of various cis-acting elements involved in hormone response, tissue-specific expression, and stress response. Additionally, qRT-PCR results showed significant upregulation of PgCBF11 expression in stems following cold treatment, with increasing over 40-fold after 32 hours of cold treatment and about 20-fold after 8 hours of cold treatment. PgCBF21 exhibited a strong response in leaves after 8 hours of cold treatment, with expression levels rising more than 37-fold. Furthermore, through the overexpression of PgCBF21, we ascertained its capacity to enhance cold tolerance in yeast. Conclusion This study analyzed the molecular characteristics of the PgCBF family members in Pennisetum glaucum and identified several candidate genes responsive to cold stress, providing a theoretical foundation for future research on the innovative utilization of cold-resistant resources.

Agricultural expansion and intensification generally lead to a depletion in soil organic carbon (SOC). While converting cropland to grassland is a recognized strategy for SOC accumulation, the patterns of SOC accumulation under different grassland types and soil conditions remain unclear. This study evaluated the long-term effects of two perennial grasses—alfalfa (a legume) and switchgrass (a non-legume)—on SOC composition, specifically lignin phenols and amino sugars, in non-saline and saline–alkali soils, using a conventional wheat–maize rotation as a control. Our results showed that both alfalfa and switchgrass significantly enhanced SOC content compared to a wheat–maize rotation, but their accumulation pathways differed between non-saline and saline–alkali soils. In non-saline soils, increases in both lignin phenols and amino sugars (muramic acid and glucosamine) were observed under both perennial grasses. In saline–alkali soils, however, the accumulation was primarily driven by glucosamine. While no significant difference was observed in amino sugars content between the two grasses, switchgrass showed significantly higher lignin phenols content than alfalfa under saline–alkali conditions. This indicated that litter quality regulated the accumulation of plant-derived C in saline–alkali environments, but has no significant impact on the accumulation of microbial-derived C. These findings elucidate the divergent mechanisms that drive SOC sequestration following cropland-to-grassland conversion in contrasting non-saline and saline–alkali soils, highlight the dominant role of microbial processes in SOC accumulation following such conversion.