Induction of callus and establishment of cell suspension and effects on tea polyphenols in the cell suspension system of tea plants by PGRs

Abstract

The effects of different plant growth regulators (PGRs) on the accumulation of tea polyphenols were investigated using the sterile leaves of the ‘Yunkang-10’ tea seedlings in test tubes as explants. Using the MS media with a sucrose concentration of 30 g/L as the basal medium, the leaf callus was induced and subcultured in vitro. The medium containing MS + 1.0 mg/L 2,4-D + 0.8 mg/L 6-BA was the most efficient for callus induction from leaf explants, with an induction rate of 78.89%. The loose calli were subcultured in the medium containing MS + 0.5 mg/L 2,4-D + 0.3 mg/L KT. The loose calli were transferred into liquid MS medium containing 2.0 mg/L 2,4-D, 0.3 mg/L KT, and casein hydrolysate (CH) 1000 mg/L. A stable cell suspension was obtained in the ninth generation with an initial inoculum of 80 g/L. The suspension was cultured in the dark at 25 ± 2°C with 110 rpm, with the medium refreshed every 16 days. Further, the amount of tea polyphenols in the tea suspension reached the maximum in the presence of 5.0 mg/L MeJA, 1.0 mg/L SA, 1.0 mg/L GA3, 1.0 mg/L ETH and 200 μmol/L ABA, with the growth rate of 154.68% on day 4, 172.81% on day 6, 213.55% on day 2, 104.48% on day 12 and 220.77% on day 2. The ABA induced the maximum accumulation of tea polyphenols in the shortest time. In this study, a stable cell suspension system was established from the callus of tea leaves. The findings suggest that the biosynthesis of tea polyphenols might be mediated mainly via the ABA signaling pathway, with a possible crosstalk between MeJA, SA, GA3, ETH and ABA. In addition, the extraction time and amount of tea polyphenols in vitro was controlled by adding different PGRs.