Integrated Metabolomic and Transcriptomic Analysis of Nitraria Berries Indicate the Role of Flavonoids in Adaptation to High Altitude.

Background: Plants of Nitraria, belonging to the Zygophyllaceae family, are not only widely distributed at an altitude of about 1000 m but also at an altitude of about 3000 m, which is a rare phenomenon. However, little is known about the effect of altitude on the accumulation of metabolites in plants of Nitraria. Furthermore, the mechanism of the high-altitude adaptation of Nitraria has yet to be fully elucidated. Methods: In this study, metabolomics and transcriptomics were used to investigate the differential accumulation of metabolites of Nitraria berries and the regulatory mechanisms in different altitudes. Results: As a result, the biosynthesis of flavonoids is the most significant metabolic pathway in the process of adaptation to high altitude, and 5 Cyanidins, 1 Pelargonidin, 3 Petunidins, 1 Peonidin, and 4 Delphinidins are highly accumulated in high-altitude Nitraria. The results of transcriptomics showed that the structural genes C4H (2), F3H, 4CL (2), DFR (2), UFGT (2), and FLS (2) were highly expressed in high-altitude Nitraria. A network metabolism map of flavonoids was constructed, and the accumulation of differential metabolites and the expression of structural genes were analyzed for correlation. Conclusions: In summary, this study preliminarily offers a new understanding of metabolic differences and regulation mechanisms in plants of Nitraria from different altitudes.