Integrated metabolomics and transcriptomics reveal the role of calcium sugar alcohol in the regulation of phenolic acid biosynthesis in Torreya grandis nuts

Abstract

Background：Torreya grandis, a prominent tree species of the autochthonous subtropical region of China, possesses a drupe-like fruit containing a nut that is rich in nutrients and bioactive compounds. However, the effect of calcium (Ca2+) sugar alcohol (CSA), a newly developed chelated Ca2+-fertilizer, on the secondary metabolism of phenolics in T. grandis nuts is largely unknown, for which transcriptomic and metabolomic analysis was carried out. Results: Transcriptome sequencing detected 47,064 transcripts, and several phenolic acid biosynthesis pathway-related genes were identified. Correlation analysis showed that the four transcription factors, WRKY12, AP2-1, AP2-3, and AP2-4, were positively associated with the accumulation of phenolic acids. Furthermore, the binding of AP2-1 to the HCT promoter was confirmed using yeast one hybrid and dual-luciferase assays. Furthermore, the expression of HCT in Nicotiana enhanced the total flavonoid content. Conclusions: Our results indicated that a new regulatory module, Ca2+–AP2–HCT, involved in the regulation of phenolic acid biosynthesis was revealed, expanding the understanding of the role of Ca2+ fertilizers in plant secondary metabolism.