H2O2 and Ca2+-based signaling and associated ion accumulation, antioxidant systems and secondary metabolism orchestrate the response to NaCl stress in perennial ryegrass

Little is known about the interplay between Ca2+ and H2O2 signaling in stressed cool-season turfgrass. To understand better how Ca2+ and H2O2 signals are integrated to enhance grass acclimation to stress conditions, we analyzed the rearrangements of endogenous ion accumulation, antioxidant systems and secondary metabolism in roots, stems and leaves of perennial ryegrass (Lolium perenne L.) treated with exogenous Ca2+ and H2O2 under salinity. Ca2+ signaling remarkably enhanced the physiological response to salt conditions. Ca2+ signaling could maintain ROS homeostasis in stressed grass by increasing the responses of antioxidant genes, proteins and enzymes. H2O2 signaling could activate ROS homeostasis by inducing antioxidant genes but weakened Ca2+ signaling in leaves. Furthermore, the metabolic profiles revealed that sugars and sugar alcohol accounted for 49.5-88.2% of all metabolites accumulation in all treated leaves and roots. However, the accumulation of these sugars and sugar alcohols displayed opposing trends between Ca2+ and H2O2 application in salt-stressed plants, which suggests that these metabolites are the common regulatory factor for Ca2+ and H2O2 signals. These findings assist in understanding better the integrated network in Ca2+ and H2O2 of cool-season turfgrass' response to salinity.