Abiotic stress is a limiting factor in peanut production. Peanut is an important oil crop and cash crop in China. Peanut yield is vulnerable to abiotic stress due to its seeds grown underground. Jasmonic acid (JA) is essential for plant growth and defense against adversity stresses. However, the regulation and mechanism of the jasmonic acid biosynthesis pathway on peanut defense against abiotic stresses are still limitedly understood. In this study, a total of 64 genes encoding key enzymes of JA biosynthesis were identified and classified into lipoxygenases (AhLOXs), alleno oxide synthases (AhAOSs), allene oxide cyclases (AhAOCs), and 12-oxo-phytodienoic acid reductases (AhOPRs) according to gene structure, conserved motif, and phylogenetic feature. A cis-regulatory element analysis indicated that some of the genes contained stress responsive and hormone responsive elements. In addition to proteins involved in JA biosynthesis and signaling, they also interacted with proteins involved in lipid biosynthesis and stress response. Sixteen putative Ah-miRNAs were identified from four families targeting 35 key genes of JA biosynthesis. A tissue expression pattern analysis revealed that AhLOX2 was the highest expressed in leaf tissues, and AhLOX32 was the highest expressed in shoot, root, and nodule tissues. AhLOX16, AhOPR1, and AhOPR3 were up-regulated under drought stress. AhLOX16, AhAOS3, AhOPR1, and AhAOC4 had elevated transcript levels in response to cold stress. AhLOX5, AhLOX16, AhAOC3, AhOPR1, and AhOPR3 were up-regulated for expression under salt stress. Our study could provide a reference for the study of the abiotic stress resistance mechanism in peanut.

Pod size is one of the important factors affecting peanut yield. However, the metabolites relating to pod size and their biosynthesis regulatory mechanisms are still unclear. In the present study, two peanut varieties (Tif and Lps) with contrasting pod sizes were used for a comparative metabolome and transcriptome analysis. Developing peanut pods were sampled at 10, 20 and 30 days after pegging (DAP). A total of 720 metabolites were detected, most of which were lipids (20.3%), followed by phenolic acids (17.8%). There were 43, 64 and 99 metabolites identified as differentially accumulated metabolites (DAMs) at 10, 20 and 30 DAP, respectively, and flavonoids were the major DAMs between Tif and Lps at all three growth stages. Multi-omics analysis revealed that DAMs and DEGs (differentially expressed genes) were significantly enriched in the phenylpropanoid biosynthesis (ko00940) pathway, the main pathway of lignin biosynthesis, in each comparison group. The comparisons of the metabolites in the phenylpropanoid biosynthesis pathway accumulating in Tif and Lps at different growth stages revealed that the accumulation of p-coumaryl alcohol (H-monolignol) in Tif was significantly greater than that in Lps at 30 DAP. The differential expression of gene-LOC112771695, which is highly correlated with p-coumaryl alcohol and involved in the biosynthesis of monolignols, between Tif and Lps might explain the differential accumulation of p-coumaryl alcohol. The content of H-lignin in genetically diverse peanut varieties demonstrated that H-lignin content affected peanut pod size. Our findings would provide insights into the metabolic factors influencing peanut pod size and guidance for the genetic improvement of the peanut.

Phosphatidyl ethanolamine-binding proteins (PEBPs) are involved in regulating flowering time and various developmental processes. Functions and expression patterns in cultivated peanuts (Arachis hypogaea L.) remain unknown. In this study, 33 PEBP genes in cultivated peanuts were identified and divided into four subgroups: FT, TFL, MFT and FT-like. Gene structure analysis showed that orthologs from A and B genomes in cultivated peanuts had highly similar structures, but some orthologous genes have subgenomic dominance. Gene collinearity and phylogenetic analysis explain that some PEBP genes play key roles in evolution. Cis-element analysis revealed that PEBP genes are mainly regulated by hormones, light signals and stress-related pathways. Multiple PEPB genes had different expression patterns between early and late-flowering genotypes. Further detection of its response to temperature and photoperiod revealed that PEBPs ArahyM2THPA, ArahyEM6VH3, Arahy4GAQ4U, ArahyIZ8FG5, ArahyG6F3P2, ArahyLUT2QN, ArahyDYRS20 and ArahyBBG51B were the key genes controlling the flowering response to different flowering time genotypes, photoperiods and temperature. This study laid the foundation for the functional study of the PEBP gene in cultivated peanuts and the adaptation of peanuts to different environments.

Auxin plays a crucial role in regulating root growth and development, and its distribution pattern under environmental stimuli significantly influences root plasticity. Under K deficiency, the interaction between K⁺ transporters and auxin can modulate root development. This study compared the differences in root morphology and physiological mechanisms of the low-K-tolerant maize inbred line 90-21-3 and K-sensitive maize inbred line D937 under K-deficiency (K⁺ = 0.2 mM) with exogenous NAA (1-naphthaleneacetic acid, NAA = 0.01 mM) treatment. Root systems of 90-21-3 exhibited higher K⁺ absorption efficiency. Conversely, D937 seedling roots demonstrated greater plasticity and higher K⁺ content. In-depth analysis through transcriptomics and metabolomics revealed that 90-21-3 and D937 seedling roots showed differential responses to exogenous NAA under K-deficiency. In 90-21-3, upregulation of the expression of K⁺ absorption and transport-related proteins (proton-exporting ATPase and potassium transporter) and the enrichment of antioxidant-related functional genes were observed. In D937, exogenous NAA promoted the responses of genes related to intercellular ethylene and cation transport to K-deficiency. Differential metabolite enrichment analysis primarily revealed significant enrichment in flavonoid biosynthesis, tryptophan metabolism, and hormone signaling pathways. Integrated transcriptomic and metabolomic analyses revealed that phenylpropanoid biosynthesis is a crucial pathway, with core genes (related to peroxidase enzyme) and core metabolites upregulated in 90-21-3. The findings suggest that under K-deficiency, exogenous NAA induces substantial changes in maize roots, with the phenylpropanoid biosynthesis pathway playing a crucial role in the maize root’s response to exogenous NAA regulation under K-deficiency.

Salt stress is a limiting factor affecting the growth, development, and yield of peanuts. Breeding improvement is a possible solution to overcome salt stress. The salt tolerance of 57 peanut cultivars in Northeast China was identified using indoor simulation at the germination stage, the seedling stage, and field natural identification. At the germination stage, 75 mM NaCl was the most suitable screening concentration, and the seed vitality index of 57 cultivars was analyzed using the membership function and cluster analysis. Among these cultivars, 11 were identified as salt-tolerant and 19 were salt-sensitive during germination. In the seedling stage, six salt tolerance coefficients (STCs) showed significant correlation. A gray relational analysis was used in combination with evaluation grading, resulting in the identification of 14 salt-tolerant cultivars and 12 salt-sensitive cultivars. In the field screening, a comprehensive analysis was conducted using a principal component analysis of nine indices, including agronomic characteristics, yield characteristics, and SPAD. This analysis led to the determination of three comprehensive indices. The weighted membership function was used for comprehensive evaluation. Finally, three salt-tolerant cultivars and four salt-sensitive cultivars suitable for planting in Northeast China were screened out to provide an excellent germplasm for researching the salt-tolerant mechanism of peanuts.