Integrated physiological and transcriptomic analyses reveal differential photosynthetic responses to low-light stress in tall fescue cultivars

Abstract

Tall fescue (Festuca arundinacea Schreb.) is the predominant cool-season turfgrass species worldwide, but low-light (LL) stress is a primary limiting factor for turfgrass management. Studies on two tall fescue cultivars, Arid 3 and Airlie, showed that Airlie is more susceptible to LL stress than Arid 3. However, the underlying susceptibility mechanism is obscure. In this study, we investigated the physiological and transcriptional changes of two tall fescue cultivars under LL stress. Arid 3 showed better growth characteristics, higher chlorophyll contents and photosynthetic gas exchange than Airlie. A total of 136,925 unigenes were obtained from our RNA-sequencing. There were 24,944 and 30,816 differentially expressed genes (DEGs) between LL stress and the control in Arid 3 and Airlie, respectively. Meanwhile, there were 20,599 DEGs detected between Arid 3 and Airlie under the control, and under LL stress the DEGs between two cultivars were 20,783. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis suggested that the DEGs were mainly involved in ‘cell part’ and ‘glutathione metabolism’. Furthermore, vital transcription factors obtained different expression level in two cultivars. FaPhyA and FaPhyB were higher expressed in Arid 3 than that in Airlie, which played positive roles in regulating photomorphogenesis of tall fescue under LL stress. On the contrary, the expression levels of negative regulatory factor FaPIF5 and FaCOP1 were higher in Airlie. Additionally, genes related to chlorophyll metabolism and photosynthesis were also affected by LL stress, there were 26 genes significantly higher expressed in Arid 3. This study revealed two tall fescue cultivars develop different physiological and transcriptional changes, and provided an insight into different photosynthetic responses in two tall fescue cultivars responding to LL stress.