Na2CO3-responsive Photosynthetic and ROS Scavenging Mechanisms in Chloroplasts of Alkaligrass Revealed by Phosphoproteomics

Jinwei Suo,Shaojun Dai,Siyi Guo,Yongxue Zhang,Xumin Zhang,Sixue Chen,Lianwei Peng,Jun Ma,Zhi Qin,Qi Zhao,Weimin Ma,Juanjuan Yu,Heng Zhang,Ying Li,Tai Wang,Lihai Guo,Yuchen Miao,Ji Luo,Nan Zhang,Bao-Hua Song ,Yi‐Min She ,Ji Cao

doi:10.1016/j.gpb.2018.10.011

Abstract

Alkali-salinity exerts severe osmotic, ionic, and high-pH stresses to plants. To understand the alkali-salinity responsive mechanisms underlying photosynthetic modulation and reactive oxygen species (ROS) homeostasis, physiological and diverse quantitative proteomics analyses of alkaligrass (Puccinellia tenuiflora) under Na2CO3 stress were conducted. In addition, Western blot, real-time PCR, and transgenic techniques were applied to validate the proteomic results and test the functions of the Na2CO3-responsive proteins. A total of 104 and 102 Na2CO3-responsive proteins were identified in leaves and chloroplasts, respectively. In addition, 84 Na2CO3-responsive phosphoproteins were identified, including 56 new phosphorylation sites in 56 phosphoproteins from chloroplasts, which are crucial for the regulation of photosynthesis, ion transport, signal transduction, and energy homeostasis. A full-length PtFBA encoding an alkaligrass chloroplastic fructose-bisphosphate aldolase (FBA) was overexpressed in wild-type cells of cyanobacterium Synechocystis sp. Strain PCC 6803, leading to enhanced Na2CO3 tolerance. All these results indicate that thermal dissipation, state transition, cyclic electron transport, photorespiration, repair of photosystem (PS) II, PSI activity, and ROS homeostasis were altered in response to Na2CO3 stress, which help to improve our understanding of the Na2CO3-responsive mechanisms in halophytes.

Highlights

Soil salinization and alkalization frequently occur simultaneously
These results indicate that reactive oxygen species (ROS) in chloroplasts were mainly dismutated by superoxide dismutase (SOD), and subsequently reduced in ascorbate peroxidase (APX)/POD pathway under the Na2CO3 treatment
NaCl-responsive mechanisms have been well-studied in various halophytes using proteomics approaches [4], the Na2CO3-responsive proteins and corresponding regulatory mechanisms in halophytes were rarely explored

Summary

Introduction

Soil salinization and alkalization frequently occur simultaneously. In northeast China, more than 70% of the land area has become alkaline grassland [1]. Alkali-salinity is one of the most severe abiotic stresses, limiting the productivity and geographical distribution of plants. Saline-alkali stress exerts osmotic stress and ion damage, as well as high-pH stress to plants [2]. Little attention has been given to the sophisticated tolerance mechanisms underlying plant response to saline-alkali (e.g. Na2CO3 and NaHCO3) stresses [3,4]. As the organelle for photosynthesis, chloroplasts are extremely susceptible to saline-alkali stress [5]

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Results

Discussion

Conclusion