Preparation of ER Microsomes from Arabidopsis thaliana

Microsomes are vesicles derived from the endoplasmic reticulum (ER) when cells are broken down in the lab. These microsomes are a valuable tool to study a variety of ER functions such as protein and lipid synthesis in vitro. Here we describe a protocol to isolate ER-derived microsomes Arabidopsis thaliana seedlings and exemplify the use of these purified microsomes in enzyme assays with the auxin precursors tryptophan (Trp) or indole-3-pyruvic acid (IPyA) to quantify auxin synthetic capacity in microsomal and cytosolic fractions.