Kentucky bluegrass (Poa pratensis L.), a turf grass species that is hypertolerant of cadmium (Cd), is a potential phytoremediation material for soil polluted with Cd. However, the mechanism of Cd phytotoxicity in Kentucky bluegrass is unclear. Here, we compared the phenotype, induction of oxidative stress, and structural and non-structural carbohydrate contents between a Cd-tolerant genotype (‘Midnight’, M) and Cd-sensitive genotype (‘Rugby’, R). The results showed that both genotypes accumulated more Cd in the roots, whereas the R genotype distributed more Cd into the leaves compared with the M genotype. In both genotypes, Cd inhibited the length and fresh weight of the leaves and roots; increased the peroxidase (POD) activity but inhibited ascorbate peroxidase (APX) and catalase (CAT) activity; and increased the superoxide radical (O₂⁻), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) contents. However, the M genotype exhibited lower root length inhibition, and the H₂O₂ and MDA contents confirmed that the M genotype had increased Cd accumulation and resistance, while the R genotype exhibited a better distribution of Cd. Moreover, Cd stress significantly increased the soluble sugar, trehalose, and sucrose contents of both genotypes. Pectin, lignin, and cellulose were significantly increased to prevent the entry of Cd into the roots. The Cd-induced growth inhibition and physiological responses in Kentucky bluegrass were preliminarily explored herein, with the chelation of pectin, lignification, and antioxidant response being possible contributors to Cd detoxification in Kentucky bluegrass. In addition, the Cd-induced increase in trehalose, sucrose, and soluble sugar contents might play a pivotal role in the defense against Cd stress in Kentucky bluegrass.

The nutritional quality and yield of oats (Avena sativa) are often compromised by plant diseases such as red leaf, powdery mildew, and leaf spot. Sugars Will Eventually be Exported Transporters (SWEETs) are newly identified sugar transporters involved in regulating plant growth and stress responses. However, the roles of SWEET genes in biotic stress responses remain uncharacterized in oats. In this study, 13 AsSWEET genes were identified across nine chromosomes of the oat genome, all of which were predicted to contain seven transmembrane regions. Phylogenetic analysis revealed four clades of AsSWEET proteins, with high homology to SWEET proteins in the Poaceae family. Collinearity analysis demonstrated strong relationships between oat and Zea mays SWEETs. Using subcellular localization prediction tools, AsSWEET proteins were predicted to localize to the plasma membrane. Promoter analysis revealed cis-acting elements associated with light response, growth, and stress regulation. Six AsSWEET proteins were predicted to interact in a network centered on AsSWEET1a and AsSWEET11. Gene expression analysis of two oat varieties, ‘ForagePlus’ and ‘Molasses’, indicated significant expression differences in several AsSWEET genes following infection with powdery mildew or leaf spot, including AsSWEET1a, AsSWEET1b, AsSWEET2b, AsSWEET3a, AsSWEET11, and AsSWEET16. These SWEET genes are potential candidates for disease resistance in oats. This study provides a foundation for understanding the regulatory mechanisms of AsSWEET genes, particularly in response to powdery mildew and leaf spot, and offers insights for enhancing oat molecular breeding.

Background: Drought is a significant condition that restricts vegetation growth on the Tibetan Plateau. Artemisia wellbyi is a unique semi-shrub-like herb in the family Compositae, which distributed in northern and northwest of Tibetan Plateau. It is a dominant species in the community that can well adapt to virous environment stress, such as drought and low temperature. Therefore, A. wellbyi. has a potential ecological value for soil and water conservation of drought areas. Understanding the molecular mechanisms of A. wellbyi. that defense drought stress can acquire the key genes for drought resistance breeding of A. wellbyi. and provide a theoretical basis for vegetation restoration of desertification area. However, they remain unclear. Thus, our study compared the transcriptomic characteristics of drought-tolerant “11” and drought-sensitive “6” material of A. wellbyi under drought stress. Results: A total of 4875 upregulated and 4381 downregulated differentially expressed genes (DEGs) were induced by drought in the tolerant material; however, only 1931 upregulated and 4174 downregulated DEGs were induced by drought in the sensitive material. The photosynthesis and transcriptional regulation differed significantly with respect to the DEGs number and expression level. We found that CDPKs (calmodulin-like domain protein kinases), SOS3 (salt overly sensitive3), MAPKs (mitogen-activated protein kinase cascades), RLKs (receptor like kinase), and LRR-RLKs (repeat leucine-rich receptor kinase) were firstly involved in response to drought stress in drought tolerant A. wellbyi. Positive regulation of genes associated with the metabolism of ABA (abscisic acid), ET (ethylene), and IAA (indole acetic acid) could play a crucial role in the interaction with other transcriptional regulatory factors, such as MYBs (v-myb avian myeloblastosis viral oncogene homolog), AP2/EREBPs (APETALA2/ethylene-responsive element binding protein family), WRKYs, and bHLHs (basic helix-loop-helix family members) and receptor kinases, and regulate downstream genes for defense against drought stress. In addition, HSP70 (heat shock protein70) and MYB73 were considered as the hub genes because of their strong association with other DEGs. Conclusions: Positive transcriptional regulation and negative regulation of photosynthesis could be associated with better growth performance under drought stress in the drought-tolerant material. In addition, the degradation of sucrose and starch in the tolerant A. wellbyi to alleviate osmotic stress and balance excess ROS. These results highlight the candidate genes that are involved in enhancing the performance of drought-tolerant A. wellbyi and provide a theoretical basis for improving the performance of drought-resistant A. wellbyi.

Caffeic acid O-methyltransferase (COMT) is a multifunctional enzyme involved in lignin biosynthesis and plays an important role in various primary and secondary metabolic pathways, including the plant stress response. In this study, we identified 37 AsCOMT genes from the oat (Avena sativa) whole-genome database, which are distributed across 11 chromosomes. Phylogenetic analysis grouped these genes into two major subfamilies, indicating that they are highly conserved during evolution and share close relationships with COMT genes from Zea mays and Oryza sativa. Cis-acting elements analysis revealed a rich presence of regulatory motifs related to plant hormone signaling and stress responses. Expression profiling of different oat varieties infected with powdery mildew and leaf spot disease showed significant upregulation or downregulation of several AsCOMT genes (e.g., AsCOMT14, AsCOMT22, AsCOMT24, AsCOMT27). Moreover, disease-resistant oat varieties have higher lignin contents compared to susceptible varieties. Overexpression of AsCOMT23 and AsCOMT27 in tobacco leaves resulted in significantly increased lignin content, highlighting the potential of these genes in lignin biosynthesis. These results offer a preliminary exploration of the role of AsCOMT in both lignin synthesis and the plant stress response, laying the groundwork for further functional studies and potential applications in oat breeding.

The class III peroxidase (POD) gene family encodes redox enzymes involved in the catalytic processes of hydrogen peroxide, phenolic compounds, and reactive oxygen species. These enzymes play crucial roles in lignin biosynthesis and stress responses. To explore the functions of the oat (Avena sativa) POD (AsPOD) gene family in resistance to powdery mildew, we performed a genome-wide analysis and bioinformatics characterization. A total of 97 AsPOD genes were identified, unevenly distributed across 21 chromosomes. Structural predictions indicated that α-helices are the predominant structural components of AsPOD proteins, and phylogenetic analysis revealed six clades of AsPOD proteins, with high homology to POD proteins in the Poaceae family. Cis-regulatory element analysis revealed that three AsPOD genes are associated with hormone signaling, light response, and stress resistance. Analysis of duplication events in the oat POD gene family indicates that there are a total of 55 pairs of gene segment duplications among the 69 AsPOD genes. Expression profiling of powdery mildew-infected oat varieties showed significant up- or downregulation of several AsPOD genes (AsPOD51, AsPOD55, AsPOD63, AsPOD89), identifying them as key candidates for disease resistance studies. Furthermore, resistant oat varieties exhibited higher lignin content than susceptible ones. Correlation analysis indicated that AsPOD51, AsPOD55, AsPOD63, AsPOD88, and AsPOD89 showed a stronger positive association with lignin content in resistant varieties. After inoculation with the powdery mildew pathogen, the H₂O₂ content rapidly increases, and POD activity first rises and then decreases. Those findings provide a foundation for further research into the role of AsPOD genes in oat disease resistance.

Leaf spot disease has become a significant limitation in oat production. 24-epibrassinolide (EBR), a highly active brassinosteroid, plays a significant role in enhancing plant immunity against various diseases by modulating physiological and molecular responses. However, the exact mechanisms by which exogenous EBR regulates plant defense to leaf spot disease are still largely unknown. In this study, we applied various concentrations of EBR (0, 0.01, 0.1, 1, and 10 mg·L⁻¹) to the leaves of oat plants that were inoculated with the Drechslera avenae pathogen. The application of 1 mg·L⁻¹ EBR significantly decreased disease index and increased chlorophyll content under pathogen inoculation while also enhancing antioxidant enzyme (SOD, CAT, and APX) activity and reducing pathogen-induced O₂^•− production rate and MDA content. Moreover, the enzymes associated with phenylpropanoid metabolism, such as PAL, C4H, and 4CL, were significantly activated by exogenous EBR. Our transcriptomic analyses further revealed that the combination of exogenous EBR and pathogen inoculation upregulated genes involved in signal transduction (BR, ABA, and MAPK), antioxidant enzyme defense systems, and phenylpropanoid and lignin-specific pathways, such as BAS1, APX, GPX, PAL, C4H, 4CL, CCR1, and CAD. Together, these findings reveal that exogenous BR application can improve resistance to Drechslera avenae-induced leaf spot disease in oats by regulating antioxidant defense systems and phenylpropanoid metabolism, which may have the potential to control leaf spot disease in oat production.