Figure 3

Arginine-rich ER targeting sequences are conserved for GCSI between kingdoms. CLSM analysis of Nicotiana tabacum leaf epidermal cells expressing GFP fusions alone (left panels), or co-expressing GFP fusions and either the ER marker mRFP-HDEL (middle panels), or the Golgi marker ST-mRFP (right panels). Δ13GCS90 (A-C) is exclusively located in the Golgi and perfectly co-localizes with ST-mRFP (C). XYLT35 is also located in the Golgi (D-F); [44]. When GCS13-XYLT35 (G) is co-expressed with mRFP-HDEL, the ER appears in yellow and the Golgi remains green (H) whereas when GCS13-XYLT35 is co-expressed with ST-mRFP the Golgi is yellow and the ER is green (I) showing GCS13-XYLT35 has a dual location in the ER and in the Golgi. Interestingly, when the first 13 N-terminal amino acids of GCS90 are replaced by the first 10 N-terminal amino acids of the human GCSI, Hs10Δ13GCS90 is located exclusively in the ER (J) as illustrated from colocalization with mRFP-HDEL (K) and the absence of overlap for GFP and RFP signals when it is co-expressed with ST-mRFP (L). This together with data presented Table 1 suggests that arginine-rich ER targeting sequences are conserved for GCSI between kingdoms. Bars = 8 μm.