Down-regulation of arginine decarboxylase gene-expression results in reactive oxygen species accumulation in Arabidopsis.

Abstract Arabidopsis amiR: ADC -L2 is a non-lethal line with several developmental defects, it is characterized by a drastic reduction in free polyamine content. Herein, we found that catalase application had growth-promoting effects in amiR: ADC -L2 and parental Ws seedlings. Differences in ROS content between amiR: ADC -L2 and Ws seedlings were detected. Increased H 2 O 2 levels were found in the amiR: ADC -L2, as well as low AtCAT2 gene expression and reduced catalase activity. Estimation of polyamine oxidase activity in amiR: ADC -L2 line indicated that the over-accumulation of H 2 O 2 is independent of polyamine catabolism. However, increments in NADPH oxidase activity and O 2 •− content could be associated to the higher H 2 O 2 levels in the amiR: ADC -L2 line. Our data suggest that low polyamine levels in Arabidopsis seedlings are responsible for the accumulation of ROS, by altering the activities of enzymes involved in ROS production and detoxification. Highlights • ROS content and CAT activity is deregulated in a non-lethal line (amiR: ADC -L2) with low polyamine levels. • Catalase exogenous treatment induces a promoting growth in A. thaliana. • Accumulation of ROS in amiR: ADC -L2 line is independent of PA catabolism. [ABSTRACT FROM AUTHOR]