Transcript profiling of two potato cultivars during glycoalkaloid-inducing treatments shows differential expression of genes in sterol and glycoalkaloid metabolism

Nurun Nahar,Folke Sitbon,Paresh C Dutta,Lisa Beste,Kerstin Dalman,Alexandra Olarte Guasca,Lisbeth Jonsson,Usman Arif,Alexandre Huchelmann,Erik Westerberg

doi:10.1038/srep43268

Abstract

Steroidal glycoalkaloids (SGA) are sterol-derived neurotoxic defence substances present in several members of the Solanaceae. In the potato (Solanum tuberosum), high SGA levels may render tubers harmful for consumption. Tuber SGA levels depend on genetic factors, and can increase as a response to certain stresses and environmental conditions. To identify genes underlying the cultivar variation in tuber SGA levels, we investigated two potato cultivars differing in their SGA accumulation during wounding or light exposure; two known SGA-inducing treatments. Using microarray analysis coupled to sterol and SGA quantifications, we identified a small number of differentially expressed genes that were associated with increased SGA levels. Two of these genes, encoding distinct types of sterol Δ24-reductases, were by sense/antisense expression in transgenic potato plants shown to have differing roles in sterol and SGA metabolism. The results show that an increased SGA level in potato tubers during both wounding and light exposure is mediated by coordinated expression of a set of key genes in isoprenoid and steroid metabolism, and suggest that differences in this expression underlie cultivar variations in SGA levels. These results may find use within potato breeding and quality assessment.

Highlights

Solanidine, but differ in their sugar moieties
Our analyses show that steroidal glycoalkaloids (SGAs) accumulation in potato tubers during wounding and light exposure is associated with a coordinated expression of a small number of key genes in isoprenoid and steroid metabolism, and suggest that this expression underlies cultivar differences in SGA levels
Increased SGA levels in potato tubers are preceded by a cholesterol increase

Summary

Introduction

Solanidine, but differ in their sugar moieties. SGAs occur in all parts of the plant, generally attaining the highest levels in flowers and berries. The transcription factor GAME9 ( called JRE4) was shown to regulate the expression in tomato and potato of genes in the isoprenoid and SGA biosynthesis pathways[23,24]. We hypothesized that genes relevant for increased SGA biosynthesis would fulfil at least three criteria: (i) be up-regulated by both wounding and light; (ii) be more strongly induced in King Edward than in Bintje; and (iii) be induced before, or parallel to, increased SGA levels. Our analyses show that SGA accumulation in potato tubers during wounding and light exposure is associated with a coordinated expression of a small number of key genes in isoprenoid and steroid metabolism, and suggest that this expression underlies cultivar differences in SGA levels

Methods

Results

Discussion

Conclusion