Title: Regulatory role of Ca2+ and NO in salicylic acid (SA) induced signaling against Ni2+-induced toxicity in Anabaena sp. PCC 7120
Running Head: Ca2+ and NO in SA signaling against Ni2+- toxicity
Authors: Nidhi Verma, Parul Parihar, Rachana Singh*, Sheo Mohan Prasad*, Aparna Pandey
Affiliation: Ranjan Plant Physiology and Biochemistry Laboratory, Department of Botany, University of Allahabad, Prayagraj- 211002 India.
Emailing addresses:nidhi111verma@gmail.com (N. Verma), parulprhr336@gmail.com (P. Parihar)
*Corresponding authors’ email:rachanaranjansingh@gmail.com (R. Singh), profsmprasad@gmail.com (S.M. Prasad)
Contributed equally
Abstract: Present study deals with the regulation of SA induced Ca2+-mediated NO signaling in cyanobacteriumAnabaena PCC 7120. Nickel (Ni2+)-toxicity strongly inhibited growth (DW), exopolysaccharides, photosynthetic pigments, PSII photochemistry (OJIP transient parameters:Fm , Fv ,Fm/Fo ,Fv/Fo , Ψo ,ФPo , ФEo , Area ,N , and PIABS were suppressed; whileFo , Fo/Fm ,Fo/Fv , Sm ,ФDo , ABS/RC ,TRo/RC , ETo/RC andDIo/RC were raised), nitrogen metabolism status and non-enzymatic antioxidant system by increasing intracellular Ni2+ accumulation and excessive ROS production. However, salicylic acid (SA), calcium (CaCl2) and sodium nitroprusside (SNP) addition to the culture medium counteracted on negative impact of Ni2+ thereby improving the growth. Further, to investigate the relation between Ca2+ and NO, when c-PTIO was supplemented to Ni+SA+Ca and EGTA to Ni+SA+NO treated culture medium, the recovery on above studied traits caused due to Ca2+ and NO was arrested even in presence of SA to Ni2+-stressed Anabaena cells thereby suggesting the signaling behavior of Ca2+ and NO in SA induced pathway; however, the impact was worsened under c-PTIO supplemented Ni+SA+Ca than EGTA supplemented Ni+SA+NO treatment thereby suggesting key role of NO in SA-induced Ca2+-mediated signaling. Additionally, NO accumulation, intracellular Ni2+accumulation, ROS and indices, and non-enzymatic antioxidant system were also examined that showed varied results.