Genome-wide identification and expression analysis of glutathione S-transferase gene family in tomato: Gaining an insight to their physiological and stress-specific roles.

Shiful Islam,Iffat Ara Rahman,Tahmina Islam,Ajit Ghosh,Debasis Chakrabarty

doi:10.1371/journal.pone.0187504

Shiful Islam, Iffat Ara Rahman + Show 3 more

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https://doi.org/10.1371/journal.pone.0187504

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Abstract

Glutathione S-transferase (GST) refers to one of the major detoxifying enzymes that plays an important role in different abiotic and biotic stress modulation pathways of plant. The present study aimed to a comprehensive genome-wide functional characterization of GST genes and proteins in tomato (Solanum lycopersicum L.). The whole genome sequence analysis revealed the presence of 90 GST genes in tomato, the largest GST gene family reported till date. Eight segmental duplicated gene pairs might contribute significantly to the expansion of SlGST gene family. Based on phylogenetic analysis of tomato, rice, and Arabidopsis GST proteins, GST family members could be further divided into ten classes. Members of each orthologous class showed high conservancy among themselves. Tau and lambda are the major classes of tomato; while tau and phi are the major classes for rice and Arabidopsis. Chromosomal localization revealed highly uneven distribution of SlGST genes in 13 different chromosomes, where chromosome 9 possessed the highest number of genes. Based on publicly available microarray data, expression analysis of 30 available SlGST genes exhibited a differential pattern in all the analyzed tissues and developmental stages. Moreover, most of the members showed highly induced expression in response to multiple biotic and abiotic stress inducers that could be harmonized with the increase in total GST enzyme activity under several stress conditions. Activity of tomato GST could be enhanced further by using some positive modulators (safeners) that have been predicted through molecular docking of SlGSTU5 and ligands. Moreover, tomato GST proteins are predicted to interact with a lot of other glutathione synthesizing and utilizing enzymes such as glutathione peroxidase, glutathione reductase, glutathione synthetase and γ-glutamyltransferase. This comprehensive genome-wide analysis and expression profiling would provide a rational platform and possibility to explore the versatile role of GST genes in crop engineering.

Highlights

Glutathione S-transferases (GSTs) are phase II metabolic isozymes, found mainly in the cytosol
A total of 90 GST genes were identified in S. lycopersicum based on BLAST searches against the Sol Genomics Network (SGN) database
To classify GST members, all corresponding protein sequences were retrieved from SGN and analyzed through NCBI conserved domain database

Summary

Introduction

Glutathione S-transferases (GSTs) are phase II metabolic isozymes, found mainly in the cytosol. GSTs catalyze the conjugation of tripeptide (γ-Glu-Cys-Gly) glutathione (GSH) to a variety of substrates such as endobiotic and xenobiotic compounds for the detoxification [1]. During this process, reduced glutathione (GSH) acts as a nucleophile that attacks electrophilic carbon, nitrogen or sulfur atom containing nonpolar toxic compounds [1]. Following conjugation and incorporation of the electrophilic groups into hydrophobic toxic chemicals, GST increases their solubility and promotes further metabolic process for the sequestration into vacuole or transferred to the apoplast [2]. Due to its diverse cellular and metabolic role, it has been considered as one of the key members of plant stress modulation pathways [7]

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