Physiological and comparative proteomic analyses of saline-alkali NaHCO3-responses in leaves of halophyte Puccinellia tenuiflora

Abstract

AimsSoil alkalization imposes severe ion toxicity, osmotic stress, and high pH stress to plants, inhibiting their growth and productivity. NaHCO3 is a main component of alkaline soil. However, knowledge of the NaHCO3-responsive proteomic pattern of alkaligrass is still lacking. Alkaligrass (Puccinellia tenuiflora) is a monocotyledonous halophyte pasture widely distributed in the Songnen Plain in Northeastern China. This study aims to investigate the NaHCO3-responsive molecular mechanisms in the alkaligrass plants.MethodsAn integrative approach including photosynthetic and redox physiology, and comparative proteomics was used.ResultsNaHCO3 decreased photosynthesis, but increased nonphotochemical quenching, increased membrane electrolyte leakage of alkaligrass, and increased proline and glycine betaine concentrations in leaves. In addition, the NaHCO3 stress increased Na+ concentration and decreased K+/Na+ ratio in leaves, while Ca2+ and Mg2+ concentrations were maintained, contributing to signaling and homeostasis of ion and enzyme activity. Furthermore, O2− generation rate and H2O2 concentration were increased, and the activities of ten antioxidant enzymes and antioxidant concentrations were changed in response to the NaHCO3 stress. Proteomics revealed 90 NaHCO3-responsive proteins, 54% of which were localized in chloroplasts. They were mainly involved in signaling, photosynthesis, stress and defense, carbohydrate and energy metabolism, as well as protein synthesis, processing and turnover. Some protein abundances did not correlate well with their activities, implying that the enzyme activities were affected by NaHCO3-induced post-translational modifications.ConclusionsTo cope with the NaHCO3 stress, alkaligrass deployed multiple strategies, including triggering phospholipase D (PLD)-mediated Ca2+ signaling pathways, enhancing diverse reactive oxygen species (ROS) scavenging pathways, and regulating chloroplast protein synthesis and processing.