Staphylococcus sciuri sat-17 improved the growth of salt stressed maize (Zea mays l.) by modulated expression of stress responsive genes and anti-oxidative defence mechanisms

Plant growth promoting rhizobacteria (PGPRs), being the chief components of rhizosphere microbiota, are highly beneficial for plant growth and production. PGPR mediated salt stress tolerance is an intricate process which is governed by plant-bacterial interactions at molecular level. In an earlier study, positive impact of Staphylococcus scuiri SAT-17 inoculation on maize growth and physiology, under saline conditions, has been reported. To further elucidate this interaction at molecular level, salt tolerant and sensitive (FH-988 and FH-1137) maize genotypes were raised with or without inoculation of SAT-17 in the absence or presence of 120 mM NaCl. Expression analysis of various salt responsive genes (NHX1, H⁺-PPase, SOS1, HKT1, Cat1 and APX1) was carried out. Nutrient acquisition and translocation patterns along with few biochemical parameters were also studied. The results indicated that Na⁺ vacuolar sequestration and enhanced antioxidant enzyme activities might have accounted for the better salt tolerance potential of genotype FH-988 under salt stress. In contrast, genotype FH-1137 exhibited reduced Na⁺ vacuolar sequestration and antioxidant enzyme activities, thereby resulting in severe Na⁺ toxicity and oxidative damage under salt stress. Inoculation of SAT-17 ameliorated the salinity damage by maintaining optimum nutrient root-shoot translocation which in turn resulted in better Na⁺ homeostasis and reactive oxygen species scavenging. The results highlighted the contribution of several ion transporters, SOS pathway and antioxidant machinery in imparting salt stress tolerance in maize. The findings can be useful for devising strategies for cultivation of salt sensitive maize genotypes in saline areas thereby contributing in sustainable agricultural development.