Integrated Metabolome and Transcriptome Analysis Reveal Complex Molecular Mechanisms Underlying Selenium Response of Aloe vera L.

Aloe vera L. is an excellent resource for medication. Selenium-enriched aloe can act as a functional food to human health. To understand the molecular mechanisms underlying selenium accumulation in Aloe vera L., we characterized the metabolic and transcriptome responses of aloe leaves under different Na2SeO4 levels (0, 200, and 400 mg/L) treatments. Aloe leaves spraying with exogenous selenium fertilizer showed a significant increase in total Se content compared with those under non-treatment control, and no distinct differences were observed between 200 and 400 mg/L Se treatment. Non-targeted metabolic profiling revealed that Se treatment triggered the accumulation of antioxidants, including amino acid and derivatives, phenols, flavonoids, terpene, as well as indole derivatives. Consistent with metabolic changes following Se treatment, the transcript level of genes involved in Se assimilation and Se-response showed dramatically increase, such as those encoding sulfate transporter, antioxidants, phytohormone signaling, transcription factors, and phenols metabolites, suggesting Se assimilation generally accompanied with antioxidant and pathogen defense. This study exhibited comprehensive insights on Se response in Aloe vera L., and provided us with targeted genes for genetic engineering, thereby improving the therapeutic value of aloe.