1. WT pglct-1/mex1 pGlcT rRNA (a) (b) (c) TPT rRNA pglct-1/tpt-2 tpt-2/mex1 WT pGlcT rRNA pglct-1/tpt-2 TPT rRNA WT tpt-2 WT pGlcT rRNA pglct-2 pglct-1 Wild-type Homozygous mutant TGG TGA Fig. S1 Characterization of homozygous plastidic sugar transporter mutants. The null expression of the corresponding genes in the single (a) and double (b) mutants was confirmed by Northern blot analysis. Ethidium bromide-stained rRNAs are shown as the respective controls. (c) The homozygous mex1 allele in the pglct-1/mex1 double mutant was confirmed by sequencing, because mex1 is a single point mutation.

2. Fig. S2 Digital Northern analysis of plastidic sugar transporters. Microarray data for adult rosette leaf, roots, inflorescence stem and flower of Arabidopsis were obtained from GEO (Gene Expression Omnibus) database at the Genvestigator site (https://www.genvestigator.com) and used for the digital Northern analysis. Signal intensity pGlcT MEX1 TPT

3. Fig. S3 Maltose content of mutant and wild-type plants at the end of the day and night. Maltose content was determined in the mature leaves of 4-week-old single (pglct-1, pglct-2 and mex1) and double (pglct-1/mex1) mutants at the end of the day and night. Each point represents the mean (  SD) from four different measurements within each line. Asterisks indicate significant differences (p < 0.05, t-test) between mutant and wild-type plants. FW; fresh weight. * * * *

4. No sugar+ Glucose+ Maltose WT pglct-1/mex1 tpt-2/mex1 Fig. S4 Recovery of the defective phenotypes of the pglct-1/mex1 and tpt-2/mex1 mutants by supplying external sugars, glucose and maltose. Mutant and wild-type plants were grown on agar plates containing Gamborg B5 media complemented with 2% of each sugar. The pictures shown are of 25-day-old mutant and wild-type plants.

5. (a) (b) (c) (d) Fig. S5 Diurnal changes in glucose and fructose levels in the plastidic transporter mutants. Glucose (a and b) and fructose (c and d) contents were determined in the mature leaves of 4- week-old single (a and c) and double (b and d) mutants during the diurnal cycle. Each point represents the mean (  SD) from five different measurements within each line. Asterisks indicate significant differences (p < 0.1, t-test) between mutant and wild-type plants. The black shading in the upper bar indicates the dark period. FW; fresh weight. * * * * * * * * * * * * * * * * * * *

6. DPE2 SEX1 TUB DPE1 BAM3 PHS1 ISA3 pglct-1pglct-2 WT tpt-2 mex1 pglct-1/tpt-2 tpt-2mex1 pglct-1/mex1 Fig. S6 Effects of plastidic sugar transporter defects on the expression of starch degradation- related enzymes. Expression levels of starch degradation-related genes, isoamylase 3 (ISA3), β-amylase 3 (BAM3), disproportionating enzyme 1 (DPE1), DPE2, glucan-water dikinase (SEX1), and glucan phosphorylase (PHS1) in the middle of day were analyzed by RT-PCR. Total RNA was isolated from the leaves collected at the middle of day and night of Arabidopsis plants grown for 4 weeks. The tubulin 2 gene (TUB) was amplified as a control.