Figure 1
Time-course of growth of C. roseus suspension cultures under light v/s dark conditions. Actively growing cells from 4-day-old cultures were inoculated into MS medium supplemented with growth regulators and cultured under 16 h day/8 h dark photoperiod or under complete dark conditions. Cells were harvested on the indicated day and the fresh weight was determined. Values are expressed as the means ± SD (n = 3).
Figure 2
C. roseus cell suspension cultures. A, Compact callus clusters formed after 3 days of inoculation in the MS liquid medium. B, A dispersed cell suspension culture formed after 6 days of inoculation in the above-mentioned medium. C, Microscopic observation of six-day-old culture: arrows indicate divided cells. D, Fluorescence microscopy (495 nm excitation and 520 nm emission) of FDA-stained cells. Six-day-old cultures were used for microscopic observation and FDA staining. Bar represents 10 μm.
Figure 3
Effect of UV-B irradiation on growth of C. roseus suspension cultures. Actively growing cells from 4-day-old cultures were inoculated into fresh MS medium supplemented with growth regulators and cultured under 16 h day/8 h dark photoperiod. Cells were irradiated with UV-B on day 4 or day 6 after sub-culture or left untreated as described in materials and methods. Cell growth was measured every day by determining the fresh weight of the harvested cells. Values are expressed as the means ± SD (n = 3).
Figure 4
Medium alkalinization of C. roseus suspension cultured cells in response to UV-B irradiation. Four- and six-day-old cell suspension cultures were irradiated with UV-B for 5 min and the pH of the medium was measured at indicated times after the start of irradiation. Alkalinization Response (AR) or ΔpH was measured as described in materials and methods. Experiments were repeated with two different populations of cells and each experiment was carried out in triplicates.
Figure 5
Time-course of catharanthine and vindoline accumulation in cells irradiated with UV-B in C. roseus cell suspension cultures. Six-day-old suspension cultured cells of C. roseus were irradiated with UV-B light for 5 min or left untreated and harvested at indicated times. A, Catharanthine and B, vindoline accumulation was detected by HPLC as described in materials and methods. Values are represented as the means ± SD (n = 3).
Figure 6
Model for UV-B signaling in C. roseus.