Elucidation of Cross-Talk and Specificity of Early Response Mechanisms to Salt and PEG-Simulated Drought Stresses in Brassica napus Using Comparative Proteomic Analysis.

Junling Luo,Xiaojue Peng,Gang Wu,Xiaohong Yan,Jun Li,Shaohua Tang,Xinhua Zeng,Xiaofei Li,Daichang Yang

doi:10.1371/journal.pone.0138974

Abstract

To understand the cross-talk and specificity of the early responses of plants to salt and drought, we performed physiological and proteome analyses of Brassica napus seedlings pretreated with 245 mM NaCl or 25% polyethylene glycol (PEG) 6000 under identical osmotic pressure (-1.0 MPa). Significant decreases in water content and photosynthetic rate and excessive accumulation of compatible osmolytes and oxidative damage were observed in response to both stresses. Unexpectedly, the drought response was more severe than the salt response. We further identified 45 common differentially expressed proteins (DEPs), 143 salt-specific DEPs and 160 drought-specific DEPs by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The proteome quantitative data were then confirmed by multiple reaction monitoring (MRM). The differences in the proteomic profiles between drought-treated and salt-treated seedlings exceeded the similarities in the early stress responses. Signal perception and transduction, transport and membrane trafficking, and photosynthesis-related proteins were enriched as part of the molecular cross-talk and specificity mechanism in the early responses to the two abiotic stresses. The Ca2+ signaling, G protein-related signaling, 14-3-3 signaling pathway and phosphorylation cascades were the common signal transduction pathways shared by both salt and drought stress responses; however, the proteins with executive functions varied. These results indicate functional specialization of family proteins in response to different stresses, i.e., CDPK21, TPR, and CTR1 specific to phosphorylation cascades under early salt stress, whereas STN7 and BSL were specific to phosphorylation cascades under early drought stress. Only the calcium-binding EF-hand family protein and ZKT were clearly identified as signaling proteins that acted as cross-talk nodes for salt and drought signaling pathways. Our study provides new clues and insights for developing strategies to improve the tolerance of crops to complex, multiple environmental stresses.

Highlights

Brassica napus is the third most economically important oilseed crop in the world and is a essential source of plant oil and proteins for human consumption and animal feed [1]
We investigated the proteomic profiles of the early response of B. napus to salt and drought stresses using isobaric tags for relative and absolute quantitation (iTRAQ)-tandem mass spectrometry (MS/MS) technology
60 seedlings in one plastic pot were used for each treatment; six independent experiments were performed for each treatment, and two biological repeats were pooled from the leaf samples of three experiments per treatment

Summary

Introduction

Brassica napus is the third most economically important oilseed crop in the world and is a essential source of plant oil and proteins for human consumption and animal feed [1]. Compared to Arabidopsis, much less is known about the mechanism underlying oilseed responses to salt and drought stresses some progress has been made recently [2,3,4]. Both salt and drought severely affect crop growth and production [5, 6]. Cross-talk among Ca2+ and ABA-signaling pathways and mitogen-activated protein kinase (MAPK) cascades in drought and salt stress responses have recently been reported [8,9,10]. Much effort is required to elucidate the critical points of convergence and divergence that enable the integration of different signals

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Results

Discussion

Conclusion