SUN3/4/5 proteins regulate endoplasmic reticulum tubule formation and luminal spacing in Arabidopsis.

The endoplasmic reticulum(ER)is the processing factory of secretory proteins and the largest membrane-bound organelle with multiple interactions with the other organelles.It is a dynamic network composed of two morphologically distinct domains:tubules and sheets with constant luminal spacing(Chen et al.,2012).The ER shape is generated and modified by ER shaping proteins according to the cellular and developmental context as well as in response to environmental signals(Ridge et al.,1999;Takemoto et al.,2003).