iTRAQ-based proteomics screen for potential regulators of wheat (Triticum aestivum L.) root cell wall component response to Al stress

Abstract

Objective: The inhibition of Aluminum (Al)-induced root tip cell elongation is a major cause of plant root elongation suppression. The inhibition of root tip cell elongation is caused by a disruption of cell wall component metabolism, growth signaling, or cellular damage. The aim of this study was to identify the proteins involved in the metabolism of the root cell wall components under Al stress in the Al-tolerant wheat (Triticum aestivum L.) cultivar ET8.

Methods: Differentially expressed proteins of Al-tolerant wheat roots were screened via isobaric tags for relative and absolute quantification (iTRAQ). Furthermore, their expression changes were detected via RT-PCR analysis. The contents of major components of the cell wall and their changes in metabolic enzyme activities were also investigated.

Results: A total of 97 differentially expressed proteins from Al-tolerant wheat roots were screened and nine of these 97 proteins were root cell wall component related. The known nucleic acid sequences of proteins were 14-3-3 protein, the plasm membrane (PM) H⁺-ATPase, phospholipase D, peroxidase, and glycosyltransferase. For 14-3-3 protein, phospholipase D and peroxidase, the protein expression and mRNA expression were consistent with Al-treatment; however, for PM H⁺-ATPase and glycosyltransferase, the protein expression and mRNA expression were inconsistent under Al-stress. Furthermore, both cellulase activity and callase activity were down-regulated by Al stress, while the phenylalanineammonialyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) activities were up-regulated. Furthermore, the PM H⁺-ATPase activity was decreased in response to Al stress. In addition, the contents of callose, cellulose, lignin, and H₂O₂ varied significantly.

Conclusions: The cell wall components, relative metabolism enzymes activity, and gene expression also changed followed by protein expression changed in response to Al stress. The results suggest that Al stress leads to marked variations in metabolic enzyme activity, carbohydrate content, followed by changes of root cell components in wheat roots.

Keywords: Aluminum-toxicity; Metabolism; Proteomics; Root growth; Wheat; iTRAQ.