Nuclear factor Y (NF-Y) is a heterotrimeric transcription factor that plays an important role in various biological processes in plants, such as flowering regulation, drought resistance, and salt stress. However, few in-depth studies investigated the alfalfa NF-Y gene family. In this study, in total, 60 MsNF-Y genes, including 9 MsNF-YAs, 26 MsNF-YBs, and 25 MsNF-YCs, were identified in the alfalfa genome. The genomic locations, gene structures, protein molecular weights, conserved domains, phylogenetic relationships, and gene expression patterns in different tissues and under different stresses (cold stress, drought stress, and salt stress) of these NF-Y genes were analyzed. The illustration of the conserved domains and specific domains of the different subfamilies of the MsNF-Y genes implicates the conservation and diversity of their functions in alfalfa growth, development, and stress resistance. The gene expression analysis showed that 48 MsNF-Y genes (7 MsNF-YAs, 22 MsNF-YBs, and 19 MsNF-YCs) were expressed in all tissues at different expression levels, indicating that these genes have tissue expression specificity and different biological functions. In total, seven, seven, six, and eight MsNF-Y genes responded to cold stress, the ABA treatment, drought stress, and salt stress in alfalfa, respectively. According to the WGCNA, molecular regulatory networks related to salt stress were constructed for MsNF-YB2, MsNF-YB5, MsNF-YB7, MsNF-YB15, MsNF-YC5, and MsNF-YC6. This study could provide valuable information for further elucidating the biological functions of MsNF-Ys and improving salt tolerance and other abiotic stress resistance in alfalfa.

Nitrogen (N) deposition exhibits significant impacts on ecosystem functions and processes. Previous studies have indicated that N addition has an impact on the stoichiometry of plant leaf C:N:P ratios. However, few studies have focused on effects of N addition on belowground systems. This study aims to examine the impact of 7 years of N addition on above- and belowground C:N:P stoichiometry at plant community level in a temperate grassland located in Inner Mongolia. A 7-year field N addition experiment was conducted, which included six treatments: Cont: control; N1: 0.4 mol·m−2 N; N2: 0.8 mol·m−2 N; N3: 1.6 mol·m−2 N; N4: 2.8 mol·m−2 N; N5: 4 mol·m−2 N with six replicates. Above- and belowground plant biomass and C:N:P stoichiometry were measured and analyzed. Our results showed that N addition resulted in a reduction of aboveground C concentration, but an increase in aboveground N and P concentrations, with a decrease in C:N and C:P ratios and an increase in N:P ratio. Furthermore, the aboveground C, N, and P pools all exhibited an increase as a result of N addition. However, N addition did not have any significant effect on belowground C, N, P concentrations, ratios, pools, or stoichiometric characteristics in the soil layers of 0–10, 10–30, 30–50, and 50–100 cm. These results suggest that increasing levels of N deposition significantly alter the aboveground C:N:P stoichiometry at the plant community level, which may affect functions and processes in the grassland ecosystem, but have little effect on belowground C:N:P stoichiometry.

Melatonin (M) plays a key role in plant growth and stress tolerance; however, its role in mitigating cadmium (Cd) stress in timothy (Phleum pratense L.) remains poorly understood. In this study, timothy seedlings were exposed to four treatments: control (CK), melatonin (M), cadmium (Cd), and combined melatonin and cadmium (M + Cd) under hydroponic conditions. The results showed that M alleviated Cd-induced toxicity, as evidenced by improved biomass, photosynthetic performance, and enhanced antioxidant enzyme activities under M + Cd treatment compared with Cd alone. Transcriptomic analysis revealed that M-responsive differentially expressed genes (DEGs) under Cd stress were significantly enriched in oxidoreductase activity, catalytic activity, and phenylpropanoid biosynthesis pathways. In addition, genes related to metal transport, including heavy metal-associated (HMA) and natural resistance-associated macrophage protein (Nramp), along with antioxidant enzyme and phytohormone-related genes, displayed distinct expression patterns across treatments. Functional validation in yeast demonstrated that overexpression of the HMA gene Cluster-13128.5368 significantly enhanced Cd tolerance. Overall, M may enhance Cd tolerance in timothy by coordinating root retention and shoot detoxification. These findings provide new insights into the physiological and molecular mechanisms underlying M-mediated Cd tolerance in timothy seedlings.