Abstract
The endoplasmic reticulum (ER) has the largest surface area among all organelles and forms a dynamic polygonal networks. Recent studies over the past decade revealed several molecular systems responsible for organization of the ER structures. In plant cells, however, little is known about such mechanism. To understand it, we have isolated and characterized Arabidopsis mutants, endoplasmic reticulum morphology (ermo) (1). Here, we report ermo3 mutant that is defective in ER morphology. In ermo3 cells, a number of punctate signals upon polygonal networks and a huge aggregate surrounding the nucleus were observed. We found that ermo3 was defective not only in ER morphology but also in that of endomembrane organelles and in intracellular distribution of various organelles. The responsible gene for ermo3 encoded a member of GDSL-lipase/esterase family protein. ERMO3 had no active site, suggesting that it functions as a binding protein instead of an enzyme. We also found that ERMO3 and its homologs formed a large complex together with PYK10, suggesting a link between ERMO3 functions and ER bodies.
(1) Nakano, R. T. et al., (2009) Plant Cell.
