Fig. 4. Guard cell chloroplasts import ATP via the plastidial ATP/ADP translocator NTT1.

a Relative transcript levels of the ATP/ADP antiporter NUCLEOTIDE TRANSPORTER 1 (NTT1) and 2 (NTT2) genes in GC-enriched epidermal peels compared to leaves of wild-type plants. ACTIN 2 was used as a housekeeping gene for normalization. Values are means of two independent experiments ± SEM. Primer sequences and efficiencies are given in Supplementary Table 1. b Histochemical β-glucuronidase (GUS) staining of GCs of 21-day-old leaves of plants transformed with NTT1::promoter-GUS or NTT2::promoter-GUS. This experiment was repeated three times independently. Scale bars,10 µm. c, d Venus/CFP ratios in isolated guard cell chloroplasts (GCCs) and mesophyll cell chloroplasts (MCCs) expressing TKTP-AT1.03 after incubation for 5 min in a buffer with or without 5 mM ATP (unpaired t-tests, two-tailed at ***P < 0.001; n = 23, 29, 83, and 51, respectively; mean ± SEM; p-value: GCCs 0 mM ATP vs. 5 mM ATP = 0.1 × 10⁻³). Scale bars, 5 µm. Asterisks indicate significant statistical differences (***P < 0.001) in Venus/CFP ratios with or without exogenous ATP. Source data are provided as a source data file.