Proteome analysis of bermudagrass stolons and rhizomes provides new insights into the adaptation of plant stems to aboveground and underground growth.

ABSTRACT

As an important perennial warm-season turfgrass species, bermudagrass (Cynodon dactylon L.) forms underground-growing rhizomes and aboveground-growing stolons simultaneously, making it a fast propagating clonal plant with strong regeneration ability. In the current study, we compared the internode proteomes of rhizomes and stolons at the same developmental stage in the bermudagrass cultivar Yangjiang using iTRAQ. The results indicated that 228 protein species were differentially accumulated in the two specialized stems. In agreement with the different contents of starch, chlorophyll, anthocyanin and H2O2 in the two types of stems, photosynthesis and flavonoid biosynthesis were enriched with differentially accumulated protein species (DAPs) in stolons, whereas starch and sucrose metabolism, glycolysis, and H2O2 metabolism were enriched with DAPs in rhizomes. Burying stolons in the soil resulted in the gradual degradation of chlorophyll and anthocyanin, accumulation of starch, and increment of H2O2, which is similar to the physiological characteristics of rhizomes. These results collectively revealed that stolons and rhizomes of bermudagrass have significant differences at the proteome level and light might play important regulatory roles in the discrepancy of the proteome profiles and specialization of the two stems, providing new insights into the adaptation of plant stems to aboveground and underground growth. BIOLOGICAL SIGNIFICANCE: As two types of specialized stems that grow underground and aboveground respectively, rhizomes and stolons play important roles in overwintering and ecological invasion of many perennial and clonal plants. However, because rhizomes and stolons rarely coexist in single plant species, the differences between the two stems remain unclear at the molecular level. In this study, through an iTRAQ comparative proteomic analysis, we reported the identification of 228 differentially accumulated protein species (DAPs) in rhizomes and stolons of bermudagrass for the first time. We found that the 228 DAPs were interconnected to form protein networks in regulating diverse cellular activities and biochemical reactions. We also observed that stolons growing underground showed similar physiological activities and DAP expression as those of underground-growing rhizomes, suggesting that light might play important regulatory roles in the specialization of stolons and rhizomes. These results expanded our understanding of the mysterious adaption of plant stems to different growth conditions.