Investigation of Peroxisome Proliferator Activated Receptorγ (PPARγ) Expression in Rheum ribes and Its Role in Plant Programmed Cell Death (PCD)

PPARγ is a regulator of cellular differentiation and damage and a catalyst of lipid peroxidation, while its agonists, Thiazolidinediones, treat diabetes and cancer in humans. The molecular mechanism of therapeutic PPARγ is not fully understood. Rheum ribes is known for its healing effects in cancer and diabetes. On the other hand, the mechanisms underlying the power of Rheum ribes on diseases are unclear. To date, no study has demonstrated PPARγ expression in plants. Using the in-situ labelling method with the PPARγ antibody, we stereologically determined the PPARγ expression in radiant along with non-radiant cells in PCD stage tissues of Rheum ribes plant harvested at the flowering stage. For the first time in literature, we have proven that the existence of PPARγ is present in plants. Also, this study revealed novel association of PPARγ protein with PCD. The highest MDA (Malondialdehyde) value was found in the stem of Rheum ribes (6,1 ± 0,48 nmol/g). In addition, the highest expression of PPARγ is in the stems of Rheum ribes too (% 67). Level of lipid peroxidation was significantly associated with the expression of PPAR γ (r=0,714). Likewise, it has been revealed that PPAR γ controls lipid peroxidation in plants. The findings of this study indicate that Rheum ribes may represent a potential source of PPARγ in the context of therapy cancer and diabetes. It has also been shown that PPARγ also controls PCD and lipid peroxidation in plants.