Homeostatic influence of calcium and kinetin: Regulation of defense strategies against NaCl stress in cyanobacterium Nostoc muscorum ATCC 27893

In the present study, the possible roles of kinetin (KN, 20 nM) and calcium (Ca2+, 0.8 mM) in the alleviation of the salinity stress (50 mM NaCl) induced damage on the growth, and metabolism of cyanobacterium Nostoc muscorum ATCC 27893 was explored. The results revealed that salinity stress decreased the growth, light-harvesting pigments (chlorophyll a, carotenoids and phycobiliproteins) and exopolysaccharides (EPS) contents, photosynthesis (whole-cell oxygen evolution), and the performance of PS II photochemistry [Chl a fluorescence kinetics: maximum photosynthetic quantum yield (Fv/Fm or Phi_Po), quantum yield of electron transport flux (Phi_Eo), yield of electron transport per trapped exciton (Psi_o), size and number of active photosynthetic reaction centers (Fv/Fo) and performance index (PIABS)]. Reverse to this, enhancement of respiratory rate and values of PS II related energy flux parameters [absorption flux per reaction center (ABS/RC), trapping flux per reaction center (TRo/RC), dissipation flux per reaction center (DIo/RC), and electron transport flux per reaction center (ETo/RC)], and rise in levels of oxidative biomarkers (superoxide radical; O-2(center dot-), hydrogen peroxide; H2O2, and malonaldehyde; MDA equivalents) even under accelerated activity of enzymatic antioxidants (superoxide dismutase; SOD, peroxidase; POD, catalase; CAT and glutathione-s-transferase; GST) were observed. Kinetin in presence of Ca2+ improved the growth, pigments contents and performance of PS II photochemistry by down-regulating the oxidative stress biomarkres. Application of Ca2+ scavenger (EGTA) in KN treated samples increased the damaging effect on growth and photosynthesis by aggravating oxidative stress under NaCl stress, thereby indicating the positive role of Ca2+ in NaCl-induced toxicity alleviation by KN. The overall results suggest that Ca2+ together with KN could be applied in paddy fields to up-regulate the growth of N-2-fixing cyanobacterium Nostoc muscorum ATCC 27893, an inhabitant of paddy field under NaCl stress, hence they may be considered for sustainable agriculture. (C) 2022 Published by Elsevier B.V. on behalf of SAAB.

Automated summary

This study explores the roles of kinetin and calcium in alleviating the damage caused by salinity stress on the growth and metabolism of cyanobacterium. The results show that calcium and kinetin can mitigate the negative effects of salinity stress and improve the photosynthetic performance and growth of the cyanobacterium.