Identification and analysis of glutathione S-transferase gene family in sweet potato reveal divergent GST-mediated networks in aboveground and underground tissues in response to abiotic stresses

Na Ding,Rulin Huang,Xiaojun Zhang,Yunxiang Wu,Yonghai Luo,Huihui Cui,Aimin Wang,Ruyuan Wang

doi:10.1186/s12870-017-1179-z

Abstract

BackgroundSweet potato, a hexaploid species lacking a reference genome, is one of the most important crops in many developing countries, where abiotic stresses are a primary cause of reduction of crop yield. Glutathione S-transferases (GSTs) are multifunctional enzymes that play important roles in oxidative stress tolerance and cellular detoxification.ResultsA total of 42 putative full-length GST genes were identified from two local transcriptome databases and validated by molecular cloning and Sanger sequencing. Sequence and intraspecific phylogenetic analyses revealed extensive differentiation in their coding sequences and divided them into eight subfamilies. Interspecific phylogenetic and comparative analyses indicated that most examined GST paralogs might originate and diverge before the speciation of sweet potato. Results from large-scale RNA-seq and quantitative real-time PCR experiments exhibited extensive variation in gene-expression profiles across different tissues and varieties, which implied strong evolutionary divergence in their gene-expression regulation. Moreover, we performed five manipulated stress experiments and uncovered highly divergent stress-response patterns of sweet potato GST genes in aboveground and underground tissues.ConclusionsOur study identified a large number of sweet potato GST genes, systematically investigated their evolutionary diversification, and provides new insights into the GST-mediated stress-response mechanisms in this worldwide crop.

Highlights

Sweet potato, a hexaploid species lacking a reference genome, is one of the most important crops in many developing countries, where abiotic stresses are a primary cause of reduction of crop yield
In (b), filled boxes represent exons, whereas lines represent introns exhibited low expression levels in almost all 77 varieties. These results indicate that the expression of each Glutathione S-transferases (GSTs) gene in the tuberous root is influenced by genetic background, which varies among sweet potato cultivars
Despite great advances in sequencing technologies, it remains costly and technically challenging to obtain highquality reference genomes of genetically complex organisms [47, 48].In this study, we report 43 full-length and partial GST genes that were identified from local transcriptome databases in sweet potato, a hexaploid crop lacking a high-quality reference genome

Summary

Introduction

A hexaploid species lacking a reference genome, is one of the most important crops in many developing countries, where abiotic stresses are a primary cause of reduction of crop yield. 350002, China property and/or spatiotemporal gene-expression pattern, and eventually lead to distinct evolutionary consequences: non-functionalization, subfunctionalization, or neofunctionalization [1, 2]. A contemporary gene family in a specific species represents a set of extant genes derived from a single ancestor, as an evolutionary consequence of whole genome and/or gene duplications. Systematic investigation of a gene family, in divergence of both protein-coding sequence and gene-expression profiles, would advance our understandings towards its origin and evolution and provide important insights into gene function and application [3, 4]. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated

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