Weeds compete with crops for growth resources, causing tremendous yield losses. Paraquat is one of the three most common non-selective herbicides. To study the mechanisms of paraquat resistance, we need to trace the movement of paraquat in plants and within the cell. ¹⁴C is a radioactive carbon isotope widely used to trace substances of interest in various biological studies, especially in transport analyses. Here, we describe a detailed protocol using ¹⁴C-paraquat to demonstrate paraquat efflux in Arabidopsis protoplasts.

Low-molecular-weight (LMW) thiols are a class of highly reactive compounds due to their thiol moiety. They play important roles in the maintenance of cellular redox homeostasis, detoxification, and development. Monobromobimane (mBBr) is weakly fluorescent but selectively reacts with thiols to yield highly fluorescent thioethers (mBSR) products, which is especially useful for the quantification of LMW thiols. The stable mBSR products can be separated by high-performance liquid chromatography (HPLC) equipped with a fluorescent detector. The main cellular LMW thiols are L-cysteine, gamma-glutamylcysteine, and glutathione (GSH). The following protocol describes the extraction and quantification of L-cysteine, gamma-glutamylcysteine, and glutathione from Arabidopsis tissues as reported (Xiang and Oliver, 1998; Zhao et al., 2014; Wang et al., 2015) with minor revision. Modifications may be required if the HPLC system or the C18 column is different.