Figure 4

The N-terminal arginine residues of At GCSI contain ER localization information. CLSM analysis of Nicotiana tabacum leaf epidermal cells expressing GFP fusions alone (left panels), or co-expressing GFP fusions and the ER marker mRFP-HDEL (middle panels), or co-expressing GFP fusions together with the Golgi marker ST-mRFP (right panels). GCS90 (A) co-localizes with mRFP-HDEL (B, ER in yellow) but not with ST-mRFP (C, ER in green, Golgi in red). When the four arginine residues in position 6, 7, 10 and 12 are replaced by alanine or leucine residues, R/A GCS90 (D-F) or R/L GCS90 (G-I) accumulates exclusively in the Golgi showing that arginine residues are involved in AtGCSI ER localization. Bars = 8 μm.