Differential gene expression in tall fescue tissues in response to water deficit.

Tall fescue (Festuca arundinacea Schreb.) is a popular pasture and turf grass particularly known for drought resistance, allowing for its persistence in locations that are unfavorable for other cool-season grasses. Also, its seed-borne fungal symbiont (endophyte) Epichloë coenophiala, which resides in the crown and pseudostem, can be a contributing factor in its drought tolerance. Because it contains the apical meristems, crown survival under drought stress is critical to plant survival as well as the endophyte. In this study, we subjected tall fescue plants with their endophyte to water-deficit stress or, as controls with normal watering, then compared plant transcriptome responses in four vegetative tissues: leaf blades, pseudostem, crown, and roots. A transcript was designated a differentially expressed gene (DEG) if it exhibited at least a twofold expression difference between stress and control samples with an adjusted p value of .001. Pathway analysis of the DEGs across all tissue types included photosynthesis, carbohydrate metabolism, phytohormone biosynthesis and signaling, cellular organization, and a transcriptional regulation. While no specific pathway was observed to be differentially expressed in the crown, genes encoding auxin response factors, nuclear pore anchors, structural maintenance of chromosomes, and class XI myosin proteins were more highly differentially expressed in crown than in the other vegetative tissues, suggesting that regulation in expression of these genes in the crown may aid in survival of the meristems in the crown.