Fig. 5.

CKs modulate auxin efflux and PIN expression. (A) Accumulation of [³H]NAA in BY-2 cells. Although there is no apparent effect on the auxin accumulation in BY-2 cells when CK of different concentrations (10, 20, and 50 μM ZR) was added together with [³H]NAA (Left), the 16-hour pretreatment with 5 μM ZR led to an increase in the accumulation of [³H]NAA (Right); 2 nM [³H]NAA was used in both cases. This effect could be mimicked by addition of 10 μM NPA (Right). Error bars show SDs. (B) Relative transcription of PIN auxin transporters in hypocotyl explants at different CK concentrations and at the auxin threshold (NAA; 537 nM) as measured by qRT-PCR. The statistical significance of identified differences in comparison to the absence of exogenous CKs (t test) at alpha 0.05 and 0.01 is designated (* and **, respectively), and error bars show SDs. (C) PIN1-GFP signal (green, arrowheads) in the root-like organs of ProPIN1:PIN1-GFP hypocotyl explants at the different CK concentrations. Note that the signal is getting weaker and diffuse and disappears at the CK threshold in the case of both 2,4-D and NAA. (Scale bar: 10 μm.)