Structures and Dynamics of Metabolites in Desiccation-Tolerant S. lepidophylla Plant Whole Cells Investigated by 13C Solid-State NMR.

A small fraction of vascular plants has evolved the remarkable ability for their vegetative tissues to survive the loss of the vast majority of water and revive upon rehydration. Understanding the chemical and structural mechanisms for this desiccation tolerance is important for improving agricultural crop productivity in our changing climate. Although gas chromatography-mass spectrometry has been used to profile metabolites in desiccation-tolerant plants, these studies involve chemical extraction and hence do not provide quantitative information about insoluble species in whole plants. Here, we employ solid-state NMR spectroscopy to examine the intact leaves and stems of Selaginella lepidophylla, a well-known resurrection plant, in the hydrated resurrected state and the dry dormant state. Using rigid-selective 13C cross-polarization (CP), dynamic-selective 13C insensitive-nuclei-enhancement-by-polarization transfer (INEPT), and direct polarization 13C NMR experiments, we show that the dormant state of S. lepidophylla contains higher concentrations of dynamic lipids, most likely triglycerides, as well as higher levels of immobilized trehalose and other carbohydrates compared to the hydrated state. Two control plants that are desiccation-sensitive lack the high level of dynamic lipids, and the lipids that are present have distinct chemical shifts from those of S. lepidophylla. These results indicate that dynamic lipids play a significant role in the adaptive response of vascular plants to severe water loss.