The degradation of chlorophyll is of great significance to plant growth. The chlorophyll b reductase NOL (NYC1-like) is in charge of catalyzing the degradation of chlorophyll b and maintaining the stability of the photosystem. However, the molecular mechanisms of NOL-mediated chlorophyll degradation, senescence, and photosynthesis and its functions in other metabolic pathways remain unclear, especially in warm-season turfgrass. In this study, ZjNOL was cloned from Zoysia japonica. It is highly expressed in senescent leaves. Subcellular localization investigation showed ZjNOL is localized in the chloroplast and the bimolecular fluorescence complementation (BiFC) results proved ZjNOL interacts with ZjNYC1 in vivo. ZjNOL promoted the accumulation of abscisic acid (ABA) and carbohydrates, and the increase of SAG14 at the transcriptional level. ZjNOL simultaneously led to the excessive accumulation of reactive oxygen species (ROS), the activation of antioxidant enzymes, and the generation of oxidative stress, which in turn accelerated senescence. Chlorophyll fluorescence assay (JIP-test) analysis showed that ZjNOL inhibited photosynthetic efficiency mainly through damage to the oxygen-evolving complex. In total, these results suggest that ZjNOL promotes chlorophyll degradation and senescence and negatively affects the integrity and functionality of the photosystem. It could be a valuable candidate gene for genome editing to cultivate Z. japonica germplasm with prolonged green period and improved photosynthesis efficiency.

Perennial ryegrass ( Lolium perenne L.) is a widely used turfgrass. In this study, the effect of exogenously applied 24-epibrassinolide (EBR) on salt stress tolerance of perennial ryegrass was investigated. The results indicated that pretreatment with four concentrations of EBR (0, 0.1, 10, 1000 nM) improved salt tolerance of perennial ryegrass. Exogenous EBR treatment decreased electrolyte leakage (EL), malondialdehyde (MDA), and H ₂ O ₂ contents and enhanced the leaf relative water content (RWC), proline, soluble sugar, and soluble protein content under salt stress condition. Meanwhile, EBR reduced the accumulation of Na ⁺ and increased K ⁺ , Ca ²⁺ , and Mg ²⁺ contents in leaves after salt treatment. Moreover, EBR pretreatment also increased superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) activity, as well as ascorbic acid (AsA) and glutathione contents. These results suggested that EBR improved salt tolerance by enhancing osmotic adjustment and antioxidant defense systems in perennial ryegrass.

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.

Kentucky bluegrass (Poa pratensis L.) is a major cool-season turfgrass requiring frequent mowing. Utilization of cultivars with slow growth is a promising method to decrease mowing frequency. In this study, two dwarf mutant selections of Kentucky bluegrass (A12 and A16) induced by space mutation were analyzed for the differentially expressed genes compared with the wild type (WT) by the high-throughput RNA-Seq technology. 253,909 unigenes were obtained by de novo assembly. 24.20% of the unigenes had a significant level of amino acid sequence identity to Brachypodium distachyon proteins, followed by Hordeum vulgare with 18.72% among the non-redundant (NR) Blastx top hits. Assembled unigenes were associated with 32 pathways using KEGG orthology terms and their respective KEGG maps. Between WT and A16 libraries, 4,203 differentially expressed genes (DEGs) were identified, whereas there were 883 DEGs between WT and A12 libraries. Further investigation revealed that the DEG pathways were mainly involved in terpenoid biosynthesis and plant hormone metabolism, which might account for the differences of plant height and leaf blade color between dwarf mutant and WT plants. Our study presents the first comprehensive transcriptomic data and gene function analysis of Poa pratensis L., providing a valuable resource for future studies in plant dwarfing breeding and comparative genome analysis for Pooideae plants.

Trichoderma is internationally recognized as a biocontrol fungus for its broad-spectrum antimicrobial activity. Intriguingly, the crosstalk mechanism between the plant and Trichoderma is dynamic, depending on the Trichoderma strains and the plant species. In our previous study, the Trichoderma virens 192-45 strain showed better pathogen inhibition through the secretive non-volatile and volatile substrates. Therefore, we studied transcriptional and metabolic responses altered in creeping bentgrass (Agrostis stolonifera L.) with T. virens colonization prior to a challenge with Clarireedia homoeocarpa. This fungal pathogen causes dollar spot on various turfgrasses. When the pathogen is deficient, the importance of T. virens to the enhancement of plant growth can be seen in hormonal production and microbe signaling, such as indole-3-acrylic acid. Therefore, these substrates secreted by T. virens and induced genes related to plant growth can be the ‘pre-defense’ for ensuing pathogen attacks. During C. homoeocarpa infection, the Trichoderma–plant interaction activates defense responses through the SA- and/or JA-dependent pathway, induced by T. virens and its respective exudates, such as oleic, citric, and stearic acid. Thus, we will anticipate a combination of genetic engineering and exogenous application targeting these genes and metabolites, which could make creeping bentgrass more resistant to dollar spot and other pathogens.