Fig. 1
The N-terminal domain is involved in the functional divergence between SPA1 and SPA2. a Schematic representation of the chimeric SPA1/SPA2 domain-swap proteins DS_122-HA, DS_212-HA and DS_221-HA. “CC” represents the coiled-coil domain. All chimeric proteins were expressed in a spa1 spa2 spa3 mutant under the control of the SPA2 promoter and fused with a C-terminal HA tag. Numbers above the domains indicate the percent identical amino acids between SPA1 and SPA2. NLS indicates the site of a predicted nuclear localization sequence. b Phenotype of 4-day-old spa1 spa2 spa3 mutant seedlings carrying the indicated domain-swap constructs. Representative T2 seedlings are shown. Seedlings expressing SPA1-HA or SPA2-HA served as controls. All proteins were expressed under the control of the SPA2 promoter. Seedlings were grown in darkness, 0.05 μmol m−2 s−1 FRc (FRc), 0.01 μmol m−2 s−1 Rc (Rc) or 0.05 μmol m−2 s−1 Bc (Bc) for 4 days. Numbers indicate independent transgenic lines. c Quantification of hypocotyl length of 4-day-old DS_122-HA expressing spa1 spa2 spa3 T3 homozygous seedlings grown under various fluence rates of FRc, Rc or Bc. Error bars represent the SEM of at least 20 seedlings