Overexpression of a plant reticulon remodels the lumen of the cortical endoplasmic reticulum but does not perturb protein transport.

We have cloned a member of the reticulon family of Arabidopsis thaliana (RTNLB13). When fused to YFP and expressed in tobacco leaf epidermal cells, RTNLB13 is localised in the endoplasmic reticulum. Co-expression of a soluble ER luminal marker reveals that YFP tagged, myc tagged or untagged RTNLB13 induce severe morphological changes to the lumen of the ER. We show using FRAP analysis that RTNLB13 overepression greatly reduces diffusion of soluble proteins within the ER lumen, possibly by introducing constrictions into the membrane. In spite of this severe phenotype, Golgi shape, number and dynamics appear unperturbed and secretion of a reporter protein remains unaffected.