Physiological and Transcriptome Analysis of Drought-Tolerant Mutant ds-1 of Blue Fescue (Festuca glauca) Under Drought Stress

Blue fescue (Festuca glauca) is a widely used ornamental grass worldwide. Drought is an important limiting factor for the growth and development of blue fescue; therefore, cultivating new strains of blue fescue with a strong drought tolerance is of great significance for its production practice. To investigate the drought tolerance mechanism of ds-1, this study subjected both ds-1 and “Festina” to a natural drought treatment and measured their physiological and biochemical indicators. A transcriptomic analysis was also conducted to explore the underlying molecular mechanisms. The results showed that, after the drought treatment, the relative water content (RWC), water use efficiency (WUE), and photosynthetic rate (Pn) of ds-1 leaves were significantly higher than those of “Festina”; in addition, the contents of H2O2 and O2−, the relative electrical conductivity (REC), the malondialdehyde (MDA) content, the gas conductance (Gs), and the transpiration rate (Tr) were significantly lower than those of “Festina”. The peroxidase (POD) activity of ds-1 was significantly higher than that of “Festina”, while the superoxide dismutase (SOD) activity of ds-1 was significantly lower than that of “Festina”. The transcriptome data analysis showed that there were a total of 9475 differentially expressed genes (DEGs) between ds-1 and “Festina”. A Venn plot analysis showed 692 DEGs between ds-1—8d vs. “Festina”—8d and ds-1—16d vs. “Festina”—16d. A KEGG enrichment analysis showed that these 692 genes were mainly enriched in 86 pathways, including those related to the photosynthesis antenna protein, plant hormone signal transduction, MAPK signaling, starch and sucrose metabolism, and arginine and proline metabolism. Further screening identified genes that may be associated with drought stress, including PYL, PP2C, SnRK2, ABF, BRI1, JAZ, MYC2, Lhc, and MPK6. The qRT-PCR results indicated that the expression trends of the DEGs were consistent with the transcriptome sequencing results. Our research results can provide a basis for exploring candidate genes for drought tolerance in blue fescue. In addition, our research results provide valuable genetic resources for the development of drought-resistant ornamental grass varieties, which can help reduce water consumption in cities and decrease labor and capital investment.