The procedure of in vitro propagation of Harpagophytum procumbens using shoot tips was developed. Shoot tips were cultured on Schenk and Hildebrandt (SH) agar medium supplemented with 0.57 µM indole-3-acetic acid (IAA) in combination with various cytokinins: 6-benzylaminopurine (BAP), thidiazurone (TDZ), kinetin or zeatin at four concentrations (2, 4, 6 or 8 µM). The best shoot multiplication rate (11.2 shoots/explant for 5 weeks) was achieved in the presence of 6 µM TDZ. The shoots were small and their elongation on SH medium supplemented with gibberellic acid (GA3 ) was necessary. Shoots of H. procumbens were rooted on full-strength or half-strength Murashige and Skoog (MS) agar medium either with or without auxin. Plantlets were transferred into pots and maintained in the greenhouse. After 1 month, the overall survival of plants was 83% but it decreased to 27% after 6 months.
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Opracowano procedurę mikrorozmnażania Harpagophytum procumbens przy użyciu wierzchołków pędów. Wierzchołki pędów hodowano na agarowym podłożu Schenka i Hildebrandta (SH) uzupełnionym kwasem indolilo-3-octowym (IAA) w stężeniu 0.57 µM i jedną z cytokinin: 6-benzyloaminopuryną (BAP), tidiazuronem (TDZ), kinetyną lub zeatyną w czterech różnych stężeniach (2, 4, 6 lub 8 µM). Najwyższy współczynnik mnożenia pędów (11,2 z jednego eksplantatu w ciągu 5 tygodni) osiągnięto w obecności 6 µM TDZ. Pędy były krótkie i konieczne było ich wydłużanie na podłożu SH uzupełnionym kwasem giberelinowym (GA3 ). Pędy H. procumbens ukorzeniano na agarowym podłożu Murashige i Skooga (MS) z całkowitą lub obniżoną do połowy zawartością makro- i mikroelementów, bez auksyn lub z ich dodatkiem. Roślinki przenoszono do doniczek i hodowano w szklarni. Po miesiącu przeżywało 83% roślin, ale procent ten obniżał się do 27% po 6 miesiącach.
The effects of thidiazuron (TDZ) pretreatment of shoot tips on Harpagophytum procumbens shoot proliferation and successive stages of micropropagation, i.e. rooting of regenerated shoots and acclimatization of plantlets to ex vitro conditions, were described in the present study. The best response in terms of shoot proliferation (about seven shoots/explant) and shoot length (3.2 ± 0.4 cm) was obtained when explants pretreated with 25 μmol L⁻¹ TDZ for 6 h were cultured on Schenk and Hildebrandt medium containing indole-3-acetic acid (IAA) (0.57 μmol L⁻¹) and 6-benzylaminopurine (BAP) (8 μmol L⁻¹). Under these conditions, a 330 % increase in shoot multiplication over TDZ non-pretreatment culture was achieved and TDZ pretreatment shoots were longer compared to those in control culture (2.6 ± 0.3 cm). The TDZ pretreatment did not affect the percentage of rooted shoots, length of roots and number of roots formed per shoot. The rooted plantlets were transplanted from in vitro to pots with soil and grown during 1 year in the greenhouse. The hardening process was difficult and time-consuming. We found that the plants developed from the TDZ pretreated culture were superior to plants from non-pretreated culture in terms of survival rate and morphological features, such as shoot length, leaf size, flowering and earlier root tuberisation. Random amplified polymorphic DNA and inter-simple sequence repeat analyses of pretreatment with TDZ plants showed genetic similarity to non-pretreatment plants. We conclude that applying the strategy of initial explant pretreatment with TDZ may be valuable for the improvement in H. procumbens in vitro propagation.
A genetic transformation method using Agrobacterium rhizogenes was developed for Harpagophytum procumbens. The influence of three factors on hairy root formation was tested: bacterial strains (A4 and ATCC 15834), various types of explants and acetosyringone (AS) (200 µM). The highest frequency of transformation (over 50% of explants forming roots at the infected sites after 6 weeks of culture on Lloyd and McCown (WP) medium) was achieved using a combination of nodal stem explants and A. rhizogenes strain A4. The addition of 200 µM AS to root induction medium was found to enhance hairy root induction but its effect varied depending on bacterial strain and explant type. Three of the most vigorously growing hairy root clones of H. procumbens were chosen and analyzed for accumulation of iridoid and phenylethanoid glycosides. The transgenic nature of these root clones was confirmed by PCR amplification; they were positive for rolB and rolC genes. Harpagoside, verbascoside and isoverbascoside were identified by HPLC and LC–ESI-MS as the major compounds from all analyzed hairy root clones. The Hp-3 root clone showed the higher harpagoside content (0.32 mg g⁻¹ dry wt.) compared with other analyzed transformed and non-tuberized untransformed roots of H. procumbens. However, the level of the compound in the hairy root clone was lower than that detected in a sample of commercially available root tubers of H. procumbens. The Hp-3 root clone also produced high amounts of verbascoside and isoverbascoside (8.12 mg g⁻¹ dry wt. and 9.97 mg g⁻¹ dry wt., respectively) comparable to those found in root tubers.
The promoter, 5' UTR, and 34-nt 5' fragments of protein encoding region of the Salvia miltiorrhiza copalyl diphosphate synthase gene were cloned and characterized. No tandem repeats, miRNA binding sites, or CpNpG islands were observed in the promoter, 5' UTR, or protein encoding fragments. The entire isolated promoter and 5' UTR is 2235 bp long and contains repetitions of many cis-active elements, recognized by homologous transcription factors, found in Arabidopsis thaliana and other plant species. A pyrimidine-rich fragment with only 6 non-pyrimidine bases was localized in the 33-nt stretch from nt 2185 to 2217 in the 5' UTR. The observed cis-active sequences are potential binding sites for trans-factors that could regulate spatio-temporal CPS gene expression in response to biotic and abiotic stress conditions. Obtained results are initially verified by in silico and co-expression studies based on A. thaliana microarray data.
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