Abstract
The endoplasmic reticulum (ER) body is an ER structure that is specific to the Brassicales. It accumulates a large amount of the beta-glucosidase PYK10, possibly for defense against pathogens and herbivores. However, how the ER body is formed has not been explored. Using Arabidopsis thaliana genes, we were succeeded in the formation of ER bodies in onion (Allium cepa), which is a non-Brassicales plant and does not normally form ER bodies. In Arabidopsis, a transcription factor NAI1 regulates the expression of PYK10 and functionally unknown NAI2 (1). We identified two integral membrane proteins of ER body by in-silico analysis of NAI1, and termed MEMBRANE PROTEIN OF ER BODY 1 (MEB1) and MEB2. Interestingly, co-expression of NAI2 and PYK10 is necessary and sufficient for ER body formation in the epidermal cells of onion. NAI2 physically interacted with PYK10 and two membrane proteins, MEB1 and MEB2. Our findings indicate that the NAI2-induced accumulation of matrix and membrane proteins of the ER body is necessary and sufficient for ER body formation.
(1) Yamada et al., (2008) Plant Cell. 20, 2529-2540.
