Lipid Remodeling and Membrane Stability Contribute to Differential Chilling Tolerance in Two Dichondra (Dichondra repens) Genotypes

Dichondra (<i>Dichondra repens</i>) is an important thermophilic Chinese herbal medicine and a key component in traditional herbal tea and beverages. It is also commonly used as an excellent ground cover plant for landscapes and cover cropping in orchards. In temperate and transition zones, thermophilic dichondra often suffers from chilling stress resulting in growth retardation and yield loss. This study aims to compare differences in photochemical efficiency, cell membrane stability, lipid peroxidation, and global lipid remodeling between two dichondra genotypes (chilling-tolerant Dr5 and chilling-sensitive Dr17) in response to a prolonged chilling stress. The results demonstrated that chilling stress significantly accelerated membrane lipid peroxidation and chlorophyll loss, resulting in reduced cell membrane stability and photochemical efficiency in two genotypes. However, Dr5 exhibits less oxidative damage, better cell membrane stability, and higher photochemical efficiency than Dr17 under chilling stress. The analysis of lipidomics found that both Dr5 and Dr17 accumulated phospholipids (Phls), glycoglycerolipids (Glls), and sphingolipids (Spls). More importantly, Dr5 exhibited 95%, 72%, 71%, 526%, 39%, 89%, 131%, 695%, or 865% increase in phosphatidic acid (PA), ceramide (Cer), hexosyl ceramide (Hex1Cer), lyso PA (LPA), lyso phosphatidylcholine (LPC), lyso phosphatidylethanolamine (LPE), lyso phosphatidylglycerol (LPG), lyso phosphatidylinositol (LPI), or lyso phosphatidylserine (LPS) content than Dr17 on day 10 of chilling stress, respectively. Dr5 also maintained significantly higher contents of PC (52%), PE (53%), PI (24%), PS (81%), PG (30%), and digalactosyl diacylglycerol (DGDG, 53%) after 20 days of chilling stress. In addition, two genotypes could maintain a stable unsaturation level of total lipids under chilling stress. These findings indicate that lipid remodeling is attributed to genetic variation in chilling tolerance of dichondra species. The current study provides an interesting data set that could be the starting point for analyzing the underlying mechanisms of chilling tolerance in thermophilic dichondra species.