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. 2019 Oct 10;181(4):1459–1467. doi: 10.1104/pp.19.00460

Figure 3.

Figure 3.

PD transport is regulated by the circadian clock. Light treatment is represented by yellow, dark and treatment is represented by blue. Line i of both A and B shows the day/night cycles that would be experienced by plants if they were not transferred to new light regimes. A, After growing in 16-h-light/8-h-dark cycles, N. benthamiana leaves were agroinfiltrated at dawn or dusk (as indicated by red infiltration arrows) to express GFP. GFP movement was then assayed after 48 h (as indicated by green observation arrows) of continued light/dark cycles (lines ii and iii), or 48 h of constant light starting at the end of the day (line iv), or constant darkness starting at the end of the night (line v). Constant light did not affect PD transport, but constant darkness significantly decreased PD transport (**, P < 10−23; ns, not significant). B, PD transport was assayed in mock-treated plants (TRV::GUS) that had been growing in 12-h-light/12-h-dark cycles and then transferred to constant dark conditions; GFP movement was assayed 72 h after agroinfiltration. Subjective days and nights are shown in line i. Treatment with 12 h of light during the second subjective day after agroinfiltration (line iii) strongly increased PD transport compared with PD transport in constant dark (line ii), but treatment with 12 h of light during the second subjective night (line iv) had no significant effect on PD transport. C, Leaves of mock-treated plants (left) or TRV::LHY knockdowns (right) under 12-h-light/12-h-dark photoperiod conditions were agroinfiltrated to express GFP at subjective dawn. Plants were transferred to the dark and either maintained in complete darkness for 72 h (dark gray bars) or exposed to 12 h of light during the second subjective night (light gray bars) or 12 h of light during the second subjective day (white bars). Mock-treated plants distinguished between light applied during subjective night or subjective day, significantly increasing PD transport only after exposure to light during the day. TRV::LHY knockdowns did not distinguish between subjective night or subjective day, significantly increasing PD transport after exposure to light during either time period. **, P < 10−7; ns, not significant.