Study of Arabidopsis Rud3 Proteins Involved in ER-to-Golgi Anterograde Protein Trafficking

Abstract

Newly synthesized proteins are targeted to Endoplasmic reticulum (ER) to be sorted, packaged, and later then to be transported. In Golgi dependent protein trafficking, protein from ER will be packaged to COPII vesicle and transported to Golgi for further process and modification. Several proteins, such as vesicle cargo and SNAREs, play important role in transport of COPII vesicle to Golgi. It was found the existence of Golgin, Golgi-localized protein, to be involved in membrane fusion in animal and yeast. They involve as tethering factor, ensuring the pairing of V-SNARE and T-SNARE. Rud3A and Rud3B are Golgin candidates found in Arabidopsis. Homologues of Rud3 in yeast, animal, and Drosophila had been found to be Golgi-localized proteins and involved in ER-Golgi anterograde and retrograde transport as the tethering factor. In this study, localization of Arabidopsis Rud3 proteins and their involvement in ER-to-Golgi anterograde protein trafficking were investigated. It was found that Arabidopsis Rud3A and Rud3B are localized to Golgi apparatus. As for their involvement in ER-to-Golgi trafficking, it was found that the deletion mutant of Arabidopsis Rud3 proteins caused inhibition in trafficking of FN:GFP and AALP:GFP, but not H+ATPase:GFP and Invertase:GFP. Furthermore, the overexpression of Rud3A and Rud3B enhanced the trafficking of AALP:GFP, but not Invertase:GFP. Based on this finding, this study proposes that Arabidopsis Rud3 proteins are involved in ER-to-Golgi anterograde protein trafficking and the possibility that these proteins work specifically to certain cargo protein. Further studies are needed to confirm the possibility of cargo specificity of Arabidopsis Rud3 proteins.