Auxin and hydrogen peroxide (H2O2) interaction differentially regulate seedling growth, Na+/K+ ratio and H2S homeostasis accompanying NaCl stress in etiolated sunflower (Helianthus annuus L. cv. Microgreen) seedling roots and cotyledons

Abstract

Although H2S has been reported to modulate auxin and H2O2 signaling during abiotic stress, no reports decipher the interactive roles of exogenous auxin and H2O2 on the regulation of endogenous H2S homeostasis. In the present work, auxin (IAA) and hydrogen peroxide (H2O2) interaction appear to be crucial in regulating Na+/K+ homeostasis, recovery in seedling growth and H2S accumulation in NaCl-stressed sunflower seedlings. Interestingly, impairment in endogenous IAA transport (TIBA application) also impacts H2S accumulation in the roots and cotyledons. IAA supplementation is effective in reducing Na+/K+ ratio and electrolytic leakage in roots, which reverses in the presence of TIBA (polar auxin transport inhibitor) application. IAA and H2O2-mediated modulation of H2S content corroborates with l-DES activity in seedling roots and cotyledons. In contrast to cotyledons, roots exhibited a reduction in H2S content in the presence of treatments (IAA and H2O2). H2O2 supplementation seems to partially circumvent the changes caused by the disruption of auxin transport. Thus, we hypothesize that auxin might imply H2O2 as a crucial signaling component in the regulation of H2S levels in sunflower tissues. To sum up, IAA and H2O2 interaction regulates root growth, LR proliferation, Na+/K+ ratio, and H2S metabolism in sunflower seedling roots.