Integrated Analyses of Metabolomic Profiling and Associated Gene Expression of Catharanthus roseus Seedling Reveal the Metabolic Alternations of Primary Metabolites and Flavonoids During the Apical Hook Opening Phase

In plants, apical hook opening is critical for the post-germination stage and subsequent photomorphogenesis, and this process is activated by a luminous environment. Primary and secondary metabolites are universally distributed in plants and play vital roles in seedling development and stress response. However, little is known about the metabolic dynamics in response to light during the apical hook opening phase so far. To throw further light on this omission, we performed dark- and light-grown seedling by examining widely non-targeted metabolomics and a full-scale detection of flavonoids in virtue of GC-MS and LC-QTOF/MS strategy, respectively, in the model medicinal plant Catharanthus roseus. Results herein revealed the strong differences focusing on metabolites distribution in response to light stimulus during the apical hook opening phase. In terms of primary metabolites, the sugar derivatives increased upon light exposure except for several special sugars, such as glucose, fucose, and galactose. Nevertheless, amino acids and several acids were stored in etiolated seedling, which was probably regarded as connecting with C/N balance. Strangely, in terms of flavonoids, flavonols caused by FLS gene expression were dramatically promoted in etiolation whereas reduced during de-etiolation, which likely associated with auxin asymmetric distribution by acting as an inhibitor of auxin transport. Therefore, we proposed a metabolic network elaborating the metabolite dynamics in a light-dependent manner during the apical hook opening phase. Our global view of metabolites alterations in C. roseus provided a new insight into uncovering the complex metabolic changes for the post-germination growth in seedling establishment.