Research on the Content of Plumbago auriculata (L.) Hairy Roots Mediated by Agrobacterium Rhizogenes and Its Plumbagin

Abstract

Abstract Agrobacterium rhizogene-mediated genetic transformation of hairy roots is an effective method to obtain secondary metabolites. In accordance with different genotypes, it is very specific and difficult to set up a stable genetic transformation system. The plumbagin is found in the roots of Plumbago auriculata L., a secondary metabolite with significant medicinal value, but the common root grows slowly, its accumulation period is lengthy (2–6 years). In this paper, we first explored the most effective A. rhizogene-mediated (A4, ATCC 15834, and LBA 9402) genetic transformation to induce hairy root of P. auriculata, and evaluated the plumbagin concentration in different root. The results showed that the leaves were soaked with bacterial solution for 25–30 min and then transferred to 1/2 MS + AS 100 µmol·L− 1 solid medium without preculture for 2-5d. After co culture, the leaves were transferred to 1/2 MS + Cef and sterilized with cefotaxime sodium. Under this scheme, all strains can induce hairy roots, with ATCC 15834 having the highest hairy root induction rate (86.78 ± 0.74%) and the earliest root emergence time (8.33 ± 0.58 d). 1-month-grown hairy root showed an increase in plumbagin content compared with the root of the same age group and 1-year-old live seedlings, with PAHR 15834 having the highest content of 38.95 mg·g− 1 DW, which was 72.13 times higher than the same age group and 3.95 times higher than that of 1-year-old live seedlings. This is an important experimental basis for further investigation of the biosynthesis mechanism of plumbagin and the feasibility of subsequent commercial production.