Specialization of the Stems into Shoots, Stolons, and Rhizomes in Bermudagrass (Cynodon dactylon L.): Insights from Combined Metabolome and Transcriptome Analyses

As a perennial warm-season turfgrass species with great economic value, bermudagrass (Cynodon dactylon L.) simultaneously has three types of stems: shoot, stolon, and rhizome. However, molecular mechanisms underlying the specialization of the three types of stems remain poorly understood. In this study, the metabolome differences among the three types of stems were analyzed and compared through untargeted metabolomic profiling in combination with transcriptome-wide analyses of the genes participating in the metabolic pathways. A total of 949 metabolites were identified in the three stems, whereas 303, 473, and 330 metabolites were differentially accumulated between shoots and stolons, shoots and rhizomes, and stolons and rhizomes, respectively. Sugars and phenylpropanoids were two enriched categories of metabolites showing preferential accumulation in the three types of stems. Transcriptome and RT-qPCR analyses indicated that gene expression of key enzymes catalyzing the synthesis and transformation of sugars and phenylpropanoids, especially glucose-1-phosphate adenylyltransferase, starch synthase, and phenylalanine ammonia-lyase, were delicately regulated to maintain the sugar-starch and lignin-flavonoid homeostasis in the three stems. The results of this study not only expanded our understanding of metabolism regulation in bermudagrass, but also laid a foundation for molecular mechanism study of stem specialization in this glamorous plant species.