Functional and Integrative Analysis of the Proteomic Profile of Radish Root under Pb Exposure.

Yan Wang,Liang Xu,Mingjia Tang,Wei Zhang,Wei Chen,Liwang Liu,Haiyan Jiang,Ronghua Wang

doi:10.3389/fpls.2016.01871

Abstract

Lead (Pb) is one of the most abundant heavy metal (HM) pollutants, which can penetrate the plant through the root and then enter the food chain causing potential health risks for human beings. Radish is an important root vegetable crop worldwide. To investigate the mechanism underlying plant response to Pb stress in radish, the protein profile changes of radish roots respectively upon Pb(NO3)2 at 500 mg L−1(Pb500) and 1000 mg L−1(Pb1000), were comprehensively analyzed using iTRAQ (Isobaric Tag for Relative and Absolute Quantification). A total of 3898 protein species were successfully detected and 2141 were quantified. Among them, a subset of 721 protein species were differentially accumulated upon at least one Pb treatment, and 135 ones showed significantly abundance changes under both two Pb-stressed conditions. Many critical protein species related to protein translation, processing, and degradation, reactive oxygen species (ROS) scavenging, photosynthesis, and respiration and carbon metabolism were successfully identified. Gene Ontology (GO) and pathway enrichment analysis of the 135 differential abundance protein species (DAPS) revealed that the overrepresented GO terms included “cell wall,” “apoplast,” “response to metal ion,” “vacuole,” and “peroxidase activity,” and the critical enriched pathways were involved in “citric acid (TCA) cycle and respiratory electron transport,” “pyruvate metabolism,” “phenylalanine metabolism,” “phenylpropanoid biosynthesis,” and “carbon metabolism.” Furthermore, the integrative analysis of transcriptomic, miRNA, degradome, metabolomics and proteomic data provided a strengthened understanding of radish response to Pb stress at multiple levels. Under Pb stress, many key enzymes (i.e., ATP citrate lyase, Isocitrate dehydrogenase, fumarate hydratase and malate dehydrogenase) involved in the glycolysis and TCA cycle were severely affected, which ultimately cause alteration of some metabolites including glucose, citrate and malate. Meanwhile, a series of other defense responses including ascorbate (ASA)–glutathione (GSH) cycle for ROS scavenging and Pb-defense protein species (glutaredoxin, aldose 1-epimerase malate dehydrogenase and thioredoxin), were triggered to cope with Pb-induced injuries. These results would be helpful for further dissecting molecular mechanism underlying plant response to HM stresses, and facilitate effective management of HM contamination in vegetable crops by genetic manipulation.

Highlights

Heavy metal (HM) contamination from natural, agricultural, and industrial sources has become a worldwide public health concern, which could seriously deteriorate the environment and cause adverse impacts on human health through the food chain (Pourrut et al, 2013; Singh et al, 2016)
Because the root is considered as the vulnerable part which is affected by HM (Wang et al, 2015a), it has become of vital importance to investigate the HM-response mechanisms and explore the molecular regulatory network of tolerance and homeostasis in radish
A total of 241,107 spectra were obtained from the Isobaric tags for relative and absolute quantification (iTRAQ) LC−MS/MS proteomic analysis of these three group samples including an untreated control (CK), Pb500 and Pb1000

Summary

Introduction

Heavy metal (HM) contamination from natural, agricultural, and industrial sources has become a worldwide public health concern, which could seriously deteriorate the environment and cause adverse impacts on human health through the food chain (Pourrut et al, 2013; Singh et al, 2016). Lead (Pb) is one of the most abundant HM pollutants with no physiological function, mostly penetrating the plant through the roots and accumulating in different parts (Gupta et al, 2013; Pourrut et al, 2013). Because the root is considered as the vulnerable part which is affected by HM (Wang et al, 2015a), it has become of vital importance to investigate the HM-response mechanisms and explore the molecular regulatory network of tolerance and homeostasis in radish. A lot of Pb-responsive transcripts, miRNA and its targets were detected, which were predominately involved in stressrelated signal sensing and transduction, specific metal uptake and homeostasis, glutathione metabolism-related processes and carbohydrate metabolism-related pathways (Wang et al, 2013, 2015b)

Methods

Results

Conclusion