Growth behavior of Brassica rapa rapa hairy root line
A Murashige and Skoog-based growth medium for Brassica rapa rapahairy roots had been previously established by Samabriva
(Brassica Growth Medium (BGM)). In this study, we assayed whether
modified Gamborg B5 -based medium (B5mod) could also result in good
biomass accumulation with B. rapa rapa hairy roots, since earlier
it has been successfully used for cultivation of Solanaceae hairy
roots (Häkkinen et al., 2005; Häkkinen et al., 2014). In
addition, the growth in basic Gamborg B5 (B5) medium was studied in
parallel (Fig. 1A&B ). When the accumulation of fresh biomass
weight (FW) was evaluated, it was observed that the biomass accumulation
in studied media differed statistically (Fig. 1A ) and the
highest biomass was achieved with B5mod media. However, based on dry
weight (DW), there were no differences in biomass accumulation in the
studied media (Fig. 1B ). Differences in FW and DW results
reflected the differences in sucrose concentrations, as BGM medium
contained higher sucrose concentration (50 g/l) when compared to the
other two (30 g/l). The B. rapa rapa hairy roots grown in BGM
medium with high sucrose level did not absorb as much intracellular
water as hairy roots grown in B5 and B5mod (Fig. 1A ). Due to
the equal growth with lower sucrose level, B5mod was selected as a
cultivation medium for biomass production in the rest of the study.
In order to find out the optimal secretion induction phase, the growth
behavior of B. rapa rapa hairy root line in B5mod was detrmined
(Fig. 1C ). An increase in biomass accumulation was observed
until day 14, when stationary stage was reached. Thus, 14 days was
selected as the induction point for the test protein, eGFP secretion. As
a base line, without induction, amount up to 40 mg/l eGFP was detected
in the culture medium already after 21 days when the B5-mod medium was
applied (Fig. 1D ).