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Summary Melilotus species are used as green manure and rotation crops worldwide and contain abundant pharmacologically active coumarins. However, there is a paucity of information on its genome and coumarin production and function. Here, we reported a chromosome‐scale assembly of Melilotus albus genome with 1.04 Gb in eight chromosomes, containing 71.42% repetitive elements. Long terminal repeat retrotransposon bursts coincided with declining of population sizes during the Quaternary glaciation. Resequencing of 94 accessions enabled insights into genetic diversity, population structure, and introgression. Melilotus officinalis had relatively larger genetic diversity than that of M. albus. The introgression existed between M. officinalis group and M. albus group, and gene flows was from M. albus to M. officinalis. Selection sweep analysis identified candidate genes associated with flower colour and coumarin biosynthesis. Combining genomics, BSA, transcriptomics, metabolomics, and biochemistry, we identified a β‐glucosidase (BGLU) gene cluster contributing to coumarin biosynthesis. MaBGLU1 function was verified by overexpression in M. albus, heterologous expression in Escherichia coli, and substrate feeding, revealing its role in scopoletin (coumarin derivative) production and showing that nonsynonymous variation drives BGLU enzyme activity divergence in Melilotus. Our work will accelerate the understanding of biologically active coumarins and their biosynthetic pathways, and contribute to genomics‐enabled Melilotus breeding.

Bermudagrass (Cynodon spp.) is one of the most widely distributed warm-season grasses globally. The growth habits and plant type of bermudagrass are strongly associated with the applied purpose of the landscape, livestock, and eco-remediation. Therefore, persistent efforts are made to investigate the genetic basis of plant type and growth habits of bermudagrass. Here, we dissect the genetic diversity of 91 wild bermudagrass resources by genome-wide association studies (GWAS) combined with weighted gene co-expression analysis (WGCNA). This work is based on the RNA-seq data and the genome of African bermudagrass (Cynodon transvaalensis Burtt Davy). Sixteen reliable single-nucleotide polymorphisms (SNPs) in transcribed regions were identified to be associated with the plant height and IAA content in diverse bermudagrass by GWAS. The integration of the results from WGCNA indicates that beta-glucosidase 31 (CdBGLU31) is a candidate gene underlying a G/A SNP signal. Furthermore, both qRT-PCR and correlation coefficient analyses indicate that CdBGLU31 might play a comprehensive role in plant height and IAA biosynthesis and signal. In addition, we observe lower plant height in Arabidopsis bglu11 mutants (homologs of CdBGLU31). It uncovers the breeding selection history of different plant types from diverse bermudagrass and provides new insights into the molecular function of CdBGLU31 both in plant types and in IAA biosynthetic pathways.

Background The β-glucosidases (BGLU) of glycoside hydrolase family 1 hydrolyze the glycosidic bond to release β-D-glucose and related ligands, which are widely involved in important physiological processes in plants. Genome-wide analysis of the BGLU genes in the model crops Arabidopsis thaliana and Oryza sativa revealed that they are functionally diverse. In contrast, the BGLU gene family in Tartary buckwheat remains unclear. Results This study identified the FtBGLU gene family based on Tartary buckwheat genomic data and analyzed the biological function of the FtBGLU gene using bioinformatics methods and the expression pattern of the gene using fluorescence quantitative PCR. The results showed that 39 BGLU genes were identified in Tartary buckwheat, which were classified into 10 subfamilies and one unclassified group. They were unevenly distributed on 10 chromosomes, and seven tandem duplication events involving 19 FtBGLU genes were observed, which mainly occurred in subfamily II. Their physicochemical properties are highly variable; however, they have relatively conserved exon-intron structures and high sequence homology in the subfamily, and most of the FtBGLUs contain conserved motifs, among which the expression products FtBGLU1 , FtBGLU17 , FtBGLU19 , FtBGLU21 , FtBGLU22 , and FtBGLU28 have no β-glucosidase activity. Additionally, we analyzed the tissue expression specificity of 10 FtBGLU genes during Tartary buckwheat growth and development and their expression patterns under adversity stress and hormone treatments. Revealing the important role of the BGLU gene family in Tartary buckwheat growth and development, as well as its response to adversity, provides strong support for further analysis of its regulatory mechanisms and functional applications. Summary A total of 39 FtBGLU genes were identified. Bioinformatics analysis of the gene structure, evolutionary relationship, and expression pattern of the Fagopyrum tataricum BGLU gene family establishes a foundation for a better understanding and future research on the Tartary buckwheat BGLU gene family.

In plants, β-glucosidases (BGLUs) are important glycoside hydrolases involved in several biological phenomena, including the response to stresses via the activation of phytohormones and the release of alpha-hydroxy nitriles to protect against stresses. Due to the importance of BGLUs in plant growth and stress response, genome-wide analyses have been conducted in Arabidopsis and rice, while not in tomato (Solanum lycopersicum). In this study, we identified 20 BGLU genes in the tomato that were unevenly distributed on nine chromosomes and divided into five subgroups. There were a variety of plant hormones and stress response cis-elements in the promoter region of the SlBGLU gene, indicating that the BGLU gene may be involved in several aspects of the tomato stress response. SlBGLU gene expression analysis showed that the BGLU gene of tomato was expressed in many tissues, especially in the roots and leaves. Transcriptome data and results of real-time quantitative reverse transcription-polymerase chain reaction showed that most SlBGLU genes could be induced by abscisic acid, chlorothalonil, NaCl and cold (4 °C), especially SlBGLU13 and SlBGLU19, which may be key BGLU genes in response to stress and hormonal stimulation in the tomato. In addition, we constructed a competing endogenous RNA (ceRNA) network, which confers a new direction for studies on the function of SlBGLU genes. These findings not only further clarify the potential function of the BGLU gene family in mediating abiotic stresses in the tomato, but also provide valuable information for the study of functional genomics of the tomato in the future.

Grafting is an important method for pecans, while the molecular mechanisms underlying graft union formation still need in-depth analysis. In the current investigation, we identified 22 BGLU genes in Carya illinoinensis (pecan) and demonstrated that CiBGLU21, a β-glucosidase-encoding gene, plays an important positive role in graft healing. The overexpression of CiBGLU21 enhanced graft survival rates and accelerated tissue regeneration, while biochemical assays confirmed its role in cell wall reinforcement and sugar metabolism. Additionally, we identified that CiWOX13 formed heterodimers with CiWOX14 to directly and synergistically activate the transcription of CiBGLU21. The current investigation revealed a CiWOX13/14-CiBGLU21 module as an important modulator of graft union formation, offering insights into improving grafting efficiency in perennial crops and advancing the understanding of cell wall dynamics during tissue regeneration.

Psychrophilic enzymes display efficient activity at moderate or low temperatures (4–25 °C) and are therefore of great interest in biotechnological industries. We previously examined the crystal structure of BglU, a psychrophilic β-glucosidase from the bacterium Micrococcus antarcticus , at 2.2 Å resolution. In structural comparison and sequence alignment with mesophilic (BglB) and thermophilic (GlyTn) counterpart enzymes, BglU showed much lower contents of Pro residue and of charged amino acids (particularly positively charged) on the accessible surface area. In the present study, we investigated the roles of specific amino acid residues in the cold adaptedness of BglU. Mutagenesis assays showed that the mutations G261R and Q448P increased optimal temperature (from 25 to 40–45 °C) at the expense of low-temperature activity, but had no notable effects on maximal activity or heat lability. Mutations A368P, T383P, and A389E significantly increased optimal temperature (from 25 to 35–40 °C) and maximal activity (~1.5-fold relative to BglU). Thermostability of A368P and A389E increased slightly at 30 °C. Mutations K163P, N228P, and H301A greatly reduced enzymatic activity—almost completely in the case of H301A. Low contents of Pro, Arg, and Glu are important factors contributing to BglU’s psychrophilic properties. Our findings will be useful in structure-based engineering of psychrophilic enzymes and in production of mutants suitable for a variety of industrial processes (e.g., food production, sewage treatment) at cold or moderate temperatures.