An efficient plant regeneration from Rhaponticum carthamoides transformed roots, enhanced caffeoylquinic acid derivatives production in pRi-transformed plants and their biological activity

Abstract

Rhaponticum carthamoides (Willd.) Iljin (Asteraceae) is an endemic plant species whose roots and rhizomes have been used for many years in traditional Siberian medicine. In this study, the transformed roots of R. carthamoides obtained after Agrobacterium rhizogenes transformation were able to spontaneously regenerate green buds and shoots. Bud and shoot regeneration was observed in more than 90% of the cultures grown in Schenk and Hildebrandt (SH) or Gamborg (B5) liquid medium with full micro- and macronutrient concentrations, under light conditions. The regeneration of shoots from transformed roots may be improved by supplementation of Murashige and Skoog (MS) agar medium with indole-3-acetic acid (IAA) and benzyladenine (BA). The shoots were multiplied on MS medium supplemented with 0.1 mg/L IAA and 0.2 mg/L BA and then rooted successfully. The transformation of the plants derived from transformed roots was confirmed by PCR analysis and Southern hybridization. The three-month-old pRi-transformed plants (TR-plants) were able to biosynthesize caffeoylquinic acid derivatives such as chlorogenic acid, and 3,5- or 4,5-di-O-caffeoylquinic acids. Plants obtained directly from seeds (SD-plants) being in the same age and grown under the same conditions as the transformed plants were used as compared material. The transformed plants demonstrated higher secondary metabolite levels and greater biomass accumulation than SD-plants. It was found that extracts from TR-plants exhibited antioxidant properties in the model of human blood plasma and inhibited the growth of A2058 human melanoma cells depending on the tested concentration. The present study demonstrated that the pRi-transformed plants of R. carthamoides may be an alternative to conventional field crops and these plants can be used as the promising source of the valuable compounds, such as caffeoylquinic acid derivatives.