Xiaoguang Wang

Tolerance to drought stress varies among peanut (Arachis hypogaea L.) cultivars, drought-tolerant cultivars maintained robust root volume coupled with inte

Drought tolerance varies among different peanut (Arachis hypogaea L.) cultivars. Here, drought responses of two cultivars, Huayu 22 (HY22) with drought tolerance and Fuhua 18 (FH18) with drought sensitivity, were compared at the morphological, physiological, biochemical, photosynthetic, and transcriptional levels. Drought stress caused wilting and curling of leaves, bending of stems, and water loss in both cultivars. There was an increase in malondialdehyde (MDA) content under prolonged drought stress, more so in FH18. But the levels of reactive oxygen species (H₂O₂) and lipid peroxidation were low in HY22. The activities of superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) were considerably elevated, corresponding with rapid increases in the accumulation of soluble proteins, soluble sugars, and proline. Transcriptional sequencing showed gene expression varied seriously in HY22, which was upregulated in both stems of two cultivars, though downregulation was less pronounced in HY22. KEGG pathway analysis revealed significant enrichment in four leaf and six stem pathways. Additionally, core genes relating to photosynthesis, carbon fixation, proline synthesis, and sucrose and starch synthesis pathways were identified by correlation analysis. Those gene expressions were variously upregulated in stems of two cultivars, especially in HY22, giving a novel view of the shoot as a whole participating in stress response.

Introduction: In maize and peanut intercropping, shading emerges as a critical factor for restricting peanut growth, yield, and quality.Methods: This study investigated the impact of 30% shade on shade-tolerant [Huayu 22 (HY22) and Fuhua 12 (FH12)] and shade-sensitive [Nonghua 11 (NH11) and Nonghua 5(NH5)] peanut varieties, with non-shaded condition as the control (CK). The effects of shade stress on plant morphology, photosynthetic characteristics, dry-matter accumulation, chloroplast ultra-microstructure, yield, and quality of different shade-tolerant peanut varieties were examined.Results: Compared to that in the control, shade stress led to an elongation of the main stem, shortening of the lateral branches, and reduction in the leaf area. However, these changes were less significant in the shade-tolerant than in the shade-sensitive peanut varieties, with minimal effect on the elongation of the main stem height and shortening of the lateral branches. Differences in leaf area became significant during the later stages of shade stress, particularly pronounced in the shade-sensitive peanut varieties. To enhance light capture by leaves, the shade-tolerant peanut varieties exhibited increased chlorophyll content and chloroplast grain-layer numbers. The decrease in the chlorophyll a/b ratio was more pronounced in the shade-tolerant than in the shade-sensitive peanut varieties, with significant differences. However, reduced activities of ribulose 1,5-biphosphate (RuBP) carboxylase/oxygenase and fructose 1,6-biphosphate aldolase (FBA) resulted in decreased net photosynthetic rates, particularly evident in the shade-sensitive peanut varieties during the late shade period. Shade stress led to decreased dry-matter accumulation, reduced weight of 100 fruits and kernels, and a significant decline in yield in the shade-sensitive cultivars. Shading also affected peanut-kernel quality. Compared with that in the control, the protein content increased and amino-acid (except cysteine) content decreased in the shade-tolerant cultivars.Discussion: Under shade stress, shade tolerant peanut varieties have increased the yield by improving the photosynthetic efficiency, which provided a reference for rational selection of shade tolerant peanut varieties in maize and peanut intercropping system.

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.

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.

Potassium (K⁺) deficiency is a key factor limiting maize growth and yield. Auxin plays an important role in maize adaptation to K⁺ deficiency, but its physiological and molecular mechanisms are largely unclear. In this study, the exogenous application of 0.01 μmol·L^–1 α-Naphthalene acetic acid (NAA) could effectively alleviate the growth inhibition of maize roots caused by K⁺ deficiency, especially in the low-K-sensitive maize inbred line D937. The transcriptome results showed that 3924 and 5458 genes were differentially expressed by exogenous NAA in D937 (sensitive to K⁺ deficiency) and 90-21-3 (tolerant to K⁺ deficiency) under K⁺ deficiency, respectively. The exogenous application of NAA to D937 results in maintenance of the indole acetic acid (IAA) levels by inducing an upregulation in the expression of YUCCA-encoding genes and decreases abscisic acid (ABA) content by inducing the differential expression of genes encoding NCED (downregulated), ABA2 (downregulated), and PP2C (upregulated), thereby reducing growth damage caused by K⁺ deficiency. In 90-21-3, exogenous NAA can decrease ABA content and increase IAA/ABA by inducing the differential expression of CYP707- and ABF-related genes, inhibiting the excess accumulation of reactive oxygen species by inducing the differential expression of genes encoding antioxidant enzymes, and maintain cellular K⁺ homeostasis by regulating the expression of genes encoding K⁺ channels and transporters, thus enhancing plant tolerance to K⁺ deficiency. This study lays the foundation for understanding the molecular mechanisms underlying maize adaptation to K⁺ deficiency.