Assessment of Gus Expression Induced by Anti-Sense Os PPO Gene Promoter and Antioxidant Enzymatic Assays in Response to Drought and Heavy Metal Stress in Transgenic Arabidopsis thaliana

Abiotic stresses, including drought and heavy metals, are detrimental to plant growth and development and enormously reduce agricultural yields. Plants may quickly change their transcriptome in response to various stressful conditions. Plants develop many defense mechanisms to respond to various stresses that can be classified into morphological, physiological, and biochemical responses. Polyphenol oxidases (PPOs) are one of the self-protective enzymes found in plants except for Arabidopsis. Currently, drought and heavy metals were applied exogenously to transgenic A. thaliana lines (transformed with Oryza sativa PPO promoter fused to the GUS reporter gene). The current study mainly focused on the systematic pathway by which plants respond to stressors. The aim of this study is to investigate the effect/expression of PPO and antioxidant defense system against abiotic stresses. A. thaliana was treated with different concentrations of polyethylene glycols. At 30% PEG, maximum fold induction (1.9) was seen after 12 h. Overall, various concentrations (5%, 20%, and 30%) induced PPO expression after 6, 12, and 24 h. Moreover, three different concentrations of Cu (50 µM, 100 µM, 200 µM) and Ni (50 µM, 100 µM, 200 µM) for 6, 12, and 24 h were also applied. It was observed that the expression profiling of the Os PPO promoter induced GUS gene expression in response to Cu and Ni treatments. The maximum fold induction (15.03) of GUS was observed in 100 µM of Cu after 24 h. In the case of Ni, maximum fold induction of (7.78) was observed at 100 µM after 24 h. So, both Cu and Ni showed a similar pattern of induction at 100 µM after 24 h. In conclusion, the efficiency of the PPOGUS promoter can be operated to assess the response of plants to various abiotic stimuli.