Exogenous Phytohormones Modulates Cypermethrin Stress in Anabaena sp. and Nostoc Muscorum: Toxicity Alleviation by Up-regulation of Ascorbate-glutathione Cycle

Abstract

Present study demonstrated the effect of phytohormones KN and IAA under cypermethrin (Cyp1; 2 µg ml− 1 and Cyp2; 4 µg ml− 1) toxicity in two nitrogen fixing cyanobacteria Nostoc muscorum ATCC 27893 and Anabaena sp. PCC 7120 by investigating growth, exopolysaccharides (EPS) contents, protein content, oxidative stress visualization inside the cell and ascorbate- glutathione cycle. Decline in growth were noticed under both the doses of cypermethrin but the decline was more (30%) at higher dose in Anabaena sp. PCC 7120 as compare to N. muscorum. This decrease was due to increased production of oxidative biomarkers (i.e. SOR and H2O2) subsequently membrane got damaged which was noticed by measuring MDA equivalents content (in vivo visualization). Kinetin and IAA alleviated the SOR and H2O2 content resulting in recovery of cellular membrane and the growth was optimized up to control level. Detoxification of H2O2 is guided by enzymes/metabolites of AsA-GSH cycle like ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorabte reductase (DHAR) activity were found to be stimulated at lower dose of cypermethrin as compare to higher dose. while the amount of metabolites: total ascorbate (AsA), total glutathione (GSH) and ratios of reduced/oxidized AsA (AsA/DHA) and GSH (GSH/GSSG) showed significant reduction at both the doses but the reduction was more at higher dose of cypermethrin. Kinetin and IAA positively regulate the AsA-GSH cycle by enhancing the activity of APX, GR, MDHAR and DHAR activity and raising the metabolites content and their reduced/oxidized ratio. This study suggests the increased enzymatic activity and AsA/DHA ratio leads to reduced production of H2O2 in the presence of both the phytohormones which further leads to enhanced growth in both the organism but the effect of KN and IAA was more pronounced in N. muscorum suggesting its resistivity against stress.