1. Figure S1 Supplemental data Time (min) SEN1 relative mRNA remaining 1 0.1 050100150 1519 dst1 ZT8 B. A. SEN1 relative mRNA remaining Time (min) 0.1 1 050100150 1519 dst1 ZT1 Figure S1. Regulation of SEN1 mRNA stability is altered in the dst1 mutant during the day. Half- life analysis was carried out as in Figure 1. Representative quantitation of the decrease in mRNA abundance for SEN1 (A) in the morning and (B) in the afternoon, respectively. Average half-life values were calculated at ZT1 and ZT8 for parental 1519 and dst1 mutant plants, respectively from at least two independent half-life experiments (A) 106 ± 14 min; 45 ± 4 min, and (B) 53 ± 2 min; 75 ± 4 min.

2. Figure S2. Circadian regulation of SEN1 mRNA stability is altered in the dst1 mutant. Half-life analysis was carried out as in Figure 6. Representative mRNA decay curves for SEN1 (A) in the subjective morning and (B) in the subjective afternoon, respectively, are shown. Average half-life values calculated at ZT1 and ZT8 for parental 1519 and dst1 mutant plants, respectively, from at least two independent half-life experiments were: (A) 159 ± 23 min; 85 ± 6 min, and (B) 55 ± 2 min; 54 ± 0 min. Figure S2 ZT8 0.1 1 050100 150 1519 dst1 SEN1 relative mRNA remaining Time (min) B. A. ZT1 SEN1 relative mRNA remaining Time (min) 1519 dst1 0.1 1 0 50 100150

3. Figure S3 Figure S3. The dst2 mutant displays a lagging circadian phase in cotyledon movement. Seedlings were grown for 5 days in 12 hr light / 12 hr dark, transferred to 24-well plates and released into continuous light. Cotyledon movement was recorded for 7 days. Each trace is the average of 5-14 individual seedlings. The experiment was repeated three times with very similar results. Hatched bars indicate subjective night.

4. Figure S4 B. A. SEN1 eIF4A 4681002121416182022( ZT hrs) 1519 Relative mRNA levels 0 0.2 0.4 0.6 0.8 1 0510152025 1519 ZT (hrs) Figure S4. Diurnal oscillation of SEN1 in the 1519 parental plants. (A) Representative Northern blot analysis of time courses performed throughout an entire day for SEN1 mRNA in parental 1519 plants. Samples consisted of 10 µg of total RNA isolated from the indicated times of the day after dawn (ZT=0). The signal for eIF4A was used as a reference for equal loading. (B) Quantitation of mRNA levels for SEN1 mRNA. All values are representative of at least two independent experiments and are made relative to the highest mRNA accumulation in either of the two genetic backgrounds.

5. 0 0.2 0.4 0.6 0.8 1 1.2 0612182430 36 42 1519 Relative mRNA levels eIF4A B. SEN1 1519 0369121518212427303336394245 (ZT hrs. ) A. Hours in continuous light Figure S5. Circadian oscillation of SEN1 in the 1519 parental plants. (A) Representative Northern blot analysis of time courses performed throughout two days in continuous light for SEN1 mRNA. RNA samples were loaded from the indicated times of the day after subjective dawn (ZT=0). (B) Quantitation of mRNA levels for SEN1. All values are representative of at least two independent experiments and are made relative to the highest mRNA accumulation. The absence of the peak at 20 hours seen under diurnal conditions in figure S4 indicates that it is dark-induced, rather than circadian-regulated. Figure S5