Genome-wide identification of C2H2-type zinc finger gene family members and their expression during abiotic stress responses in orchardgrass (Dactylis glomerata).

The C2H2-type zinc finger protein (ZFP) family is one of the largest transcription factor families in the plant kingdom and its members are involved in plant growth, development, and stress responses. As an economically valuable perennial graminaceous forage crop, orchardgrass (Dactylis glomerata) is an important feedstuff resource owing to its high yield and quality. In this study, 125 C2H2-type ZFPs in orchardgrass (Dg-ZFPs) were identified and further classified by phylogenetic analysis. The members with similar gene structures were generally clustered into the same groups, with proteins containing the conserved QALGGH motif being concentrated in groups VIII and IX. Gene ontology and miRNA target analyses indicated that Dg-ZFPs likely perform diverse biological functions through their gene interactions. The RNA-seq data revealed differentially expressed genes across tissues and development phases, suggesting that some Dg-ZFPs might participate in growth and development regulation. Abiotic stress responses of Dg-ZFP genes were verified by qPCR and Saccharomyces cerevisiae transformation, revealing that Dg-ZFP125 could enhance the tolerance of yeasts to osmotic and salt stresses. Our study performed a novel systematic analysis of Dg-ZFPs in orchardgrass, providing a reference for this gene family in other grasses and revealing new insights for enhancing gene utilization.

Genome-wide identification, phylogenetic analysis, and expression analysis of the SPL gene family in orchardgrass (Dactylis glomerata L.).

SPL (SQUAMOSA promoter binding protein-like) is a plant-specific transcription factor family that contains the conserved SBP domain, which plays a vital role in the vegetative-to-reproductive phase transition, flowering development and regulation, tillering/branching, and stress responses. Although the SPL family has been identified and characterized in various plant species, limited information about it has been obtained in orchardgrass, which is a critical forage crop worldwide. In this study, 17 putative DgSPL genes were identified among seven chromosomes, and seven groups that share similar gene structures and conserved motifs were determined by phylogenetic analysis. Of these, eight genes have potential target sites for miR156. cis-Element and gene ontology annotation analysis indicated DgSPLs may be involved in regulating development and abiotic stress responses. The expression patterns of eight DgSPL genes at five developmental stages, in five tissues, and under three stress conditions were determined by RNA-seq and qRT-PCR. These assays indicated DgSPLs are involved in vegetative-to-reproductive phase transition, floral development, and stress responses. The transient expression analysis in tobacco and heterologous expression assays in yeast indicated that miR156-targeted DG1G01828.1 and DG0G01071.1 are nucleus-localized proteins, that may respond to drought, salt, and heat stress. Our study represents the first systematic analysis of the SPL family in orchardgrass. This research provides a comprehensive assessment of the DgSPL family, which lays the foundation for further examination of the role of miR156/DgSPL in regulating development and stress responses in forages grasses.

Genome-wide identification, characterization, and expression analysis of the NAC transcription factor family in orchardgrass (Dactylis glomerata L.).

BACKGROUND: Orchardgrass (Dactylis glomerata L.) is one of the most important cool-season perennial forage grasses that is widely cultivated in the world and is highly tolerant to stressful conditions. However, little is known about the mechanisms underlying this tolerance. The NAC (NAM, ATAF1/2, and CUC2) transcription factor family is a large plant-specific gene family that actively participates in plant growth, development, and response to abiotic stress. At present, owing to the absence of genomic information, NAC genes have not been systematically studied in orchardgrass. The recent release of the complete genome sequence of orchardgrass provided a basic platform for the investigation of DgNAC proteins. RESULTS: Using the recently released orchardgrass genome database, a total of 108 NAC (DgNAC) genes were identified in the orchardgrass genome database and named based on their chromosomal location. Phylogenetic analysis showed that the DgNAC proteins were distributed in 14 subgroups based on homology with NAC proteins in Arabidopsis, including the orchardgrass-specific subgroup Dg_NAC. Gene structure analysis suggested that the number of exons varied from 1 to 15, and multitudinous DgNAC genes contained three exons. Chromosomal mapping analysis found that the DgNAC genes were unevenly distributed on seven orchardgrass chromosomes. For the gene expression analysis, the expression levels of DgNAC genes in different tissues and floral bud developmental stages were quite different. Quantitative real-time PCR analysis showed distinct expression patterns of 12 DgNAC genes in response to different abiotic stresses. The results from the RNA-seq data revealed that orchardgrass-specific NAC exhibited expression preference or specificity in diverse abiotic stress responses, and the results indicated that these genes may play an important role in the adaptation of orchardgrass under different environments. CONCLUSIONS: In the current study, a comprehensive and systematic genome-wide analysis of the NAC gene family in orchardgrass was first performed. A total of 108 NAC genes were identified in orchardgrass, and the expression of NAC genes during plant growth and floral bud development and response to various abiotic stresses were investigated. These results will be helpful for further functional characteristic descriptions of DgNAC genes and the improvement of orchardgrass in breeding programs.