Arsenic-induced stress activates sulfur metabolism in different organs of garlic (Allium sativum L.) plants accompanied by a general decline of the NADPH-generating systems in roots.

Arsenic (As) contamination is a major environmental problem which affects most living organisms from plants to animals. This metalloid poses a health risk for humans through its accumulation in crops and water. Using garlic (Allium sativum L.) plants as model crop exposed to 200µM arsenate, a comparative study among their main organs (roots and shoots) was made. The analysis of arsenic, glutathione (GSH), phytochelatins (PCs) and lipid peroxidation contents with the activities of antioxidant enzymes (catalase, superoxide dismutase, ascorbate-glutathione cycle), and the main components of the NADPH-generating system, including glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), NADP-malic enzyme (NADP-ME) and NADP-isocitrate dehydrogenase (NADP-ICDH) was carried out. Data showed a correlation among arsenic accumulation in the different organs, PCs content and the antioxidative response, with a general decline of the NADPH-generating systems in roots. Overall, our results demonstrate that there are clear connections between arsenic uptake, increase of their As-chelating capacity in roots and a decline of antioxidative enzyme activities (catalase and the ascorbate peroxidase) whose alteration provoked As-induced oxidative stress. Thus, the data suggest that roots act as barrier of arsenic mediated by a prominent sulfur metabolism which is characterized by the biosynthesis of high amount of PCs.

Separation of Plant 6-Phosphogluconate Dehydrogenase (6PGDH) Isoforms by Non-denaturing Gel Electrophoresis.

6-Phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) catalyzes the third and irreversible reaction of the pentose phosphate pathway (PPP). It carries out the oxidative decarboxylation of the 6-phosphogluconate to yield ribulose-5-phosphate, carbon dioxide and NADPH. In higher plants, 6PGDH has several subcellular localizations including cytosol, chloroplast, mitochondria and peroxisomes ( Corpas et al., 1998 ; Krepinsky et al., 2001 ; Mateos et al., 2009 ; Fernández-Fernández and Corpas, 2016; Hölscher et al., 2016 ). Using Arabidopsis thaliana as plant model and sweet pepper (Capsicum annuum L.) fruits as a plant with agronomical interest, this protocol illustrates how to prepare the plant extracts for the separation of the potential 6PGDH isoforms by electrophoresis on 6% polyacrylamide non-denaturing gels. Thus, this method allows detecting three 6PGDH isoforms in Arabidopsis seedlings and two 6PGDH isoforms in sweet pepper fruits.