An Investigation into the Effects of Cadmium and Nitric Oxide on Induced Secondary Metabolism and Antioxidant System in Pimpinella anisum L. Through Transcriptional Upregulations in AIS۱, PAL, SOD, R۲R۳-MYB, and bZIP Genes

This study was aimed to evaluate the cytoprotective role of nitric oxide (NO) against cadmium (Cd) through the potential transcriptional modifications in the expression of genes. Pimpinella anisum seedlings were treated with Cd (۰ and ۱ mM) and/or NO (۰ and ۲۵ µM). The Cd-associated decreases in shoot and root biomass were mitigated by the exogenously applied NO. Proline concentrations were increased in response to NO and/or Cd. Cd and NO treatments caused a considerable increase in peroxidase activities in comparison to the control. The individual Cd treatment led to the slight significant (p≤۰.۰۰۱) up-regulation in expression of R۲R۳-MYB transcription factor by ۲.۵ folds, while the simultaneous exposure to NO and Cd stimulated this gene by ۷.۲ folds (p≤۰.۰۰۰۱). With a similar trend, NO significantly (p≤۰.۰۰۰۱) upregulated bZIP transcription factor by ۵.۹ folds in Cd-treated seedlings.  Likewise, upregulation (۵.۲ folds) in the significant (p≤۰.۰۰۰۱) increase in expression of the phenylalanine ammonia-lyase (PAL) gene resulted from the NO+Cd application. Moreover, t-anol/isoeugenol synthase ۱ (AIS۱) gene was slightly stimulated (p≤۰.۰۵) in response to individual NO treatment. However, the Cd treatment resulted in a drastic significant (p≤۰.۰۰۰۱) increase in AIS۱ expression by ۴۲ folds which was partly declined in the Cd+NO group and reached ۲۲ folds (p≤۰.۰۰۰۱). Moreover, the NO+Cd treatment caused significant (p≤۰.۰۰۰۱) induction in the transcription of the superoxide dismutase (SOD) gene by ۱۱.۳ folds.  The correlation observed among expression patterns of mentioned genes, therefore, highlights the close interplay between the transcription factors, secondary metabolism, and antioxidant system.

Keywords:

Gene expression , Heavy metal , Pimpinella anisum , Secondary metabolism , Stress , transcription factor