Physiological, Transcriptomic and Metabolomic Analyses of Overwintering Cryptomeria fortunei Needles

Abstract

Low temperatures affect plant growth, development, and geographical distribution. Cryptomeriafortunei (Chinese cedar) is a major industrial tree species used for timber manufacturing in southern China. However, its popularization and application in northern China are limited due to its poor low-temperature resistance (approximately −6 °C), and its overwintering mechanism remains unclear. Here, we performed physiological, metabolomic, and transcriptomic analyses of overwintering C.fortunei needles at three stages: before winter, during winter, and in early spring. Physiological analyses showed that electrolyte leakage, H2O2, malondialdehyde (MDA), soluble sugar, and protein contents increased, while the maximum quantum yield of photosystem II (PSII) (Fv/Fm), effective quantum yield of PSII (YII), and chlorophyll content decreased as overwintering progressed. Metabolomic and transcriptomic analyses revealed that downregulated gibberellin (GA), salicylic acid (SA), cytokinin (CTK), and auxin signal transduction and upregulated abscisic acid (ABA), ethylene, brassinosteroids (BR), and jasmonic acid (JA) signal transduction pathways promoted the winter acclimation of C.fortunei, while the opposite expression pattern promoted the transition from dormancy to growth. In addition, upregulated genes/metabolites involved in phenylpropanoid and flavonoid biosynthesis, starch and sucrose metabolism, cold-related protein and fatty acid desaturases, and downregulated photosynthesis-related pathways promoted winter acclimation, while five (WRKY, AP2/ERF, NAC, MYB, and bHLH) and three (AP2/ERF, MYB, and bHLH) transcription factors were associated with winter acclimation and early spring transition from dormancy to growth, respectively. In summary, we report the first transcriptome of overwintering C.fortunei, providing a foundation for the cultivation of and research on overwintering varieties.