Plants of the Agropyron genus are important pasture resources, and they also play important roles in the ecological restoration. Chloroplast genomes are inherited from maternal parents, and they are important for studying species taxonomy and evolution. In this study, we sequenced the complete chloroplast genomes of five typical species of the Agropyron genus (eg., A. cristatum × A. desertorum Fisch. Schult, A. desertorum, A. desertorum Fisch. Schult. cv. Nordan, A. michnoi Roshev, and A. mongolicum Keng) using the Illumina NovaSeq platform. We found that these five chloroplast genomes exhibit a typical quadripartite structure with a conserved genome arrangement and structure. Their chloroplast genomes contain the large single-copy regions (LSC, 79,613 bp-79,634 bp), the small single-copy regions (SSC, 12,760 bp-12,768 bp), and the inverted repeat regions (IR, 43,060 bp-43,090 bp). Each of the five chloroplast genomes contains 129 genes, including 38 tRNA genes, eight rRNA genes, and 83 protein-coding genes. Among them, the genes trnG-GCC, matK, petL, ccsA, and rpl32 showed significant nucleotide diversity in these five species, and they may be used as molecular markers in taxonomic studies. Phylogenetic analysis showed that A. mongolicum is closely related to A. michnoi, while others have a closer genetic relationship with the Triticum genus.

Plant laccase genes belong to a multigene family, play key roles in lignin polymerization, and participate in the resistance of plants to biotic and abiotic stresses. Switchgrass is an important resource for forage and bioenergy production, yet information about the switchgrass laccase gene family is scarce. Using bioinformatic approaches, a genome-wide analysis of the laccase multigene family in switchgrass was carried out in this study. In total, 49 laccase genes (PvLac1 to PvLac49) were identified; these can be divided into five subclades, and 20 of them were identified as targets of miR397. The tandem and segmental duplication of laccase genes on Chr05 and Chr08 contributed to the expansion of the laccase family. The laccase proteins shared conserved signature sequences but displayed relatively low sequence similarity, indicating the potential functional diversity of switchgrass laccases. Switchgrass laccases exhibited distinct tissue/organ expression patterns, revealing that some laccases might be involved in the lignification process during stem development. All five of the laccase isoforms selected from different subclades responded to heavy metal. The immediate response of lignin-related laccases, as well as the delayed response of low-abundance laccases, to heavy-metal treatment shed light on the multiple roles of laccase isoforms in response to heavy-metal stress.

Background: Most of the grasslands in China are experiencing varying degrees of degradation, desertification, and salinization (collectively referred to as the “three degradations”), posing a serious threat to the country’s ecological security. Agropyron desertorum, known for its wide distribution, strong adaptability, and resistance, is an excellent grass species for the ecological restoration of grasslands affected by the “three degradations”. This study focused on two currently popular varieties of A. desertorum, exploring their salt tolerance mechanisms and identifying candidate genes for salt and alkali tolerance. Methods: Transcriptome sequencing was performed on two varieties of A. desertorum during the seed germination and seedling stages under varying degrees of saline–alkali stress. At the seed stage, we measured the germination rate, relative germination rate, germination index, and salt injury rate under different NaCl concentrations. During the seedling stage, physiological indicators, including superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), proline (PRO), soluble protein (SP), and catalase (CAT), were analyzed after exposure to 30, 60, 120, and 180 mM NaCl for 12 days. Analysis of differentially expressed genes (DEGs) at 6 and 24 h post-treatment with 120 mM NaCl revealed significant differences in the salt stress responses between the two cultivars. Results: Our study indicates that during the seed stage, A. desertorum (Schult.) exhibits a higher relative germination potential, relative germination rate, and relative germination index, along with a lower relative salt injury rate compared to A. desertorum cv. Nordan. Compared with A. desertorum cv. Nordan, A. desertorum (Schult.) has higher salt tolerance, which is related to its stronger antioxidant activity and different antioxidant-related pathways. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to identify the key biological processes and pathways involved in salt tolerance, including plant hormone signal transduction, antioxidant defense, and cell membrane stability. Conclusions: A. desertorum (Schult.) exhibits stronger salt tolerance than A. desertorum cv. Nordan. Salt stress at a concentration of 30–60 mM promotes the germination of the seeds of both Agropyron cultivars. The two Agropyron plants mainly overcome the damage caused by salt stress through the AsA-GSH pathway. This study provides valuable insights into the molecular mechanisms of salt tolerance in Agropyron species and lays the groundwork for future breeding programs aimed at improving salt tolerance in desert grasses.

Agropyron mongolicum is a xerophytic perennial grass with good palatability and nutritional value, predominantly distributed in sandy, arid regions and desert steppes of northwest China. However, its low biomass and limited seed yield pose significant challenges for large-scale cultivation and forage production. To date, there have been limited genomic or transcriptomic studies on A. mongolicum, particularly regarding the molecular genetic mechanisms underlying yield-related traits. In this study, we employed an integrated transcriptomic approach combining long-read sequencing (PacBio Iso-Seq) and short-read sequencing (Illumina RNA-seq) to generate a comprehensive full-length transcriptome from four tissues—leaves, stems, young spikes, and mature spikes. Transcriptomic comparisons between multi-spike and few-spike germplasms were performed to identify candidate genes involved in the regulation of spike number. A total of 762,116 full-length transcripts were generated, among which 214,500 were successfully annotated. We identified 185,424 unique genes, including 91,514 differentially expressed genes (DEGs). Functional enrichment analysis revealed 43 DEGs associated with the protein processing pathway in the endoplasmic reticulum. Notably, 8 DEGs were specifically expressed in young spikes and mature spikes of the contrasting spike-number germplasms, suggesting their potential role in spike number regulation. This study provides a high-quality transcriptomic resource and identifies candidate genes that may facilitate molecular breeding for enhanced seed yield in A. mongolicum.

Agropyron michnoi is a perennial grass with rhizomes in the genus Agropyron. It has a strong tolerance to drought and low temperature, and it is an established species in sandy flat and hilly slope lands, which constitute sandy grassland. So, it is an important forage species in dry grassland and desert steppes. Rhizomes not only enable asexual reproducibility but also confer strong resilience to stresses in A. michnoi. However, during production and utilization, it has been found that there are significant differences in the development of rhizomes among individuals of A. michnoi, yet the regulatory mechanism remains unclear. Therefore, in this study, the A. michnoi ‘Baiyinxile’ was used as the material, and the anatomical structures of the rhizomes, roots, and stems were analyzed using the paraffin sectioning technique. The results showed that the anatomical structure composition of the cross-section of the rhizome was similar to that of the root, while the arrangement of the vascular bundles in the stele was different from that of the root but similar to that of the stem. Subsequently, the Agropyron michnoi plants were classified into two types: plants with rhizomes and plants without rhizomes. Root, stem, and rhizome samples were collected from each type, and RNA sequencing was conducted. De novo transcriptomic analysis was performed to identify the candidate genes involved in rhizome development. From the RNA sequencing, a total of 103.73 Gb clean bases were obtained, from which 215,282 unigenes with an average length of 905.67 bp were assembled. Among these unigenes, 161,175 (74.87%) were functionally annotated based on seven common public databases. From pairwise comparisons of differentially expressed genes between the five samples, 129 candidate genes that are potentially specifically expressed in rhizomes were selected. Pathway enrichment analysis revealed that the rhizome-expressed genes are highly enriched in pathways of phenylpropanoid biosynthesis and starch and sucrose metabolism. The rhizome-specific expression pattern of 10 of the 129 candidate genes was further validated using qRT-PCR. Through the analysis of metabolites, 11 metabolites closely related to rhizome development, such as choline and betaine, were successfully identified. CYP family genes were selected for functional verification, and phylogenetic analysis revealed that CYP86B1 was grouped with CYP 86B1 of species such as Triticum aestivum and Lolium rigidum and was named AmrCYP86B1. The cloning results showed that its size was 1599 bp, and its subcellular localization was in the endoplasmic reticulum. Through stable genetic transformation, the study found that AmrCYP86B1 can promote the development of plant roots and stems and increase the dry matter content of the roots. Hormone detection showed that overexpression of AmrCYP 86B1 decreased the content of ABA hormone and increased the content of GA3 hormone in the plants. Combined with previous studies, it was determined that AmrCYP 86B1 promoted rhizome elongation by regulating ABA and GA3 hormones. The selected candidate genes involved in rhizome development, along with the preliminary functional verification, provide a preliminary mechanistic interpretation of rhizome development. This will contribute to in-depth research on the molecular mechanism of rhizome development in A. Michnoi.

Background: Using genomic DNA from 79 F1 plants resulted from a crossing between parents with strong and weak grazing tolerance inMedicago falcataL., we generated anEcoRIrestriction site-associated DNA (RAD) sequencing library. After sequencing and assembly, a high-density genetic map with high-quality SNP markers was constructed, with a total length of 1312.238 cM and an average density of 0.844 SNP/cM.Methods: The phenotypic traits of 79 F1 families were observed and the QTLS of 6 traits were analyzed by interval mapping.Results: Sixty three QTLs were identified for seven traits with LOD values from 3 to 6 and the contribution rates from 15% to 30%. Among the 63 QTLs, 17 were for natural shoot height, 12 for rhizome Length, 10 for Shoot canopy diameter, 9 for Basal plant diameter, 6 for stem number, 5 for absolute shoot height, and 4 for rhizome width. These QTLs were concentrated on LG2, LG4, LG5, LG7, and LG8. LG6 had only 6 QTLs. According to the results of QTL mapping, comparison of reference genomes, and functional annotation, 10 candidate genes that may be related to grazing tolerance were screened. qRT-PCR analysis showed that two candidate genes (LOC11412291 and LOC11440209) may be the key genes related to grazing tolerance ofM. falcata.Conclusion: The identified trait-associated QTLs and candidate genes in this study will provide a solid foundation for future molecular breeding for enhanced grazing-tolerance inM. falcata.