Functional Characterization of Transgenic Arabidopsis Thaliana Plants Overexpressing Aminocyclopropane-1-Carboxylic Acid Oxidase Gene

Flooding is a common natural disaster that causes severe crop and soil damage throughout the world. Studies on ethylene have proven that it is effective in improving the flood tolerance in plants. One of the vital enzymes that is involved in ethylene biosynthesis in plants, is ACC oxidase (aminocyclopropane-1-carboxylic acid oxidase) that converts aminocyclopropane -1-carboxylic acid to ethylene. Therefore, we hypothesize that overexpression of ACC oxidase gene in plants can make them flood tolerant by synthesizing more ethylene. ACC oxidase gene was PCR (Polymerase Chain Reaction) amplified from Arabidopsis thaliana and cloned into pBINmgfp5-er vector, under the control of a constitutive Cauliflower Mosaic Virus promoter. GV101 strain of Agrobacterium tumefaciens containing recombinant pBINmgfp5-er vector was used for plant transformation by the 'floral dip' procedure. The transformants were identified through kanamycin selection and grown till T3 generation (third transgenic generation). The ACC oxidase gene expression was analyzed and confirmed through quantitative PCR (qPCR). The flood tolerance was assessed by placing both control and transgenic plants on plastic trays filled with tap water that covered the soil surface. Our result shows that wild-type Arabidopsis could not survive more than 20 days under flooding while the transgenic lines remained unaffected suggesting development of flood resistance with overexpression of ACC oxidase. Moreover, the transgenic plants developed flood adaptive traits that were not common in wild type plants. This study on Arabidopsis thaliana was carried out as a 'proof of concept'. Further studies must be done to replicate the same in agriculturally-important food crops.