Physiological and comparative proteomic analyses of saline-alkali NaHCO 3 -responses in leaves of halophyte Puccinellia tenuiflora

Abstract

Aims

Soil 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.

Methods

An integrative approach including photosynthetic and redox physiology, and comparative proteomics was used.

Results

NaHCO₃ 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.

Conclusions

To 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.

from Energy Ecology Environment Ambio via Terpsi Hori on Inoreader http://bit.ly/2E0TVyF