Figure 2. Spatiotemporal development of trichomes as test system for conditional protein accumulation.

(a) Phenotype of ttg1 mutants compared with the WT. Cryo scanning electron micrographs were taken from 4-week-old plants grown constitutively at 29 or 16 °C. Scale bar, 1 mm. (b,c) Conditional complementation of ttg1 with K2:TTG1 depending on temperature and time. SEMs of 4-week-old ttg1 K2:TTG1 plants. (b) Temperature-pulsing of K2:TTG1 protein in ttg1 by short shifts from the restrictive to the permissive temperature (16 °C). Control plants were grown constitutively at restrictive (29 °C, upper row) or permissive (16 °C, bottom row) temperatures. Centre: plants grown at restrictive and shifted to permissive temperature for the time indicated (2–48 h). Red lines: borders of trichome initiation zone moving from lateral to medial with duration of the K2:TTG1 pulse. Green circles: fully mature trichomes and epidermal patterning appearing after 48 h. Arrow heads: loped circumference at trichome bases. Scale bars, 1 mm (left), 500 μm (second and third columns) and 100 μm (right). (c) WT- and ttg1-like glabrous leaves of ttg1 K2:TTG1 grown at permissive and restrictive temperatures (left two panels) or after temperature up- and downshifts during leaf development (right two panels). Arrows: direction of proximo-distal leaf development highlighting the sector affected by the temperature shift. A phenotypic comparison of different degron variants is shown in Supplementary Fig. 3, expression levels of all degron fusion genes under restrictive and permissive conditions are presented in Supplementary Fig. 4. Molecular dynamics simulations and models of the DHFR variants used are presented in Supplementary Fig. 5.