Metabolomic and transcriptomic analyses identify external conditions and key genes underlying high levels of toxic glycoalkaloids in tubers of stress-sensitive potato cultivars

Irene Merino; Alexandra Olarte Guasca; Ales Krmela; Usman Arif; Ashfaq Ali; Erik Westerberg; Siddhi Kashinanth Jalmi; Jana Hajslova; Vera Schulzova; Folke Sitbon

doi:10.3389/fpls.2023.1210850

Metabolomic and transcriptomic analyses identify external conditions and key genes underlying high levels of toxic glycoalkaloids in tubers of stress-sensitive potato cultivars

Front Plant Sci. 2023 Oct 4:14:1210850. doi: 10.3389/fpls.2023.1210850. eCollection 2023.

Affiliations

¹ Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences, and Linnean Centre for Plant Biology, Uppsala, Sweden.
² Department of Food Analysis and Nutrition, University of Chemistry and Technology Prague, Prague, Czechia.
³ National Bioinformatics Infrastructure Sweden (NBIS), SciLifeLab at Department of Immunotechnology, Lund University, Lund, Sweden.

Abstract

Introduction: High levels of toxic steroidal glycoalkaloids (SGAs) in potato tubers constitute a recognized food quality problem. Tuber SGA levels vary between potato cultivars and can increase after post-harvest stresses such as wounding and light exposure. A few cultivars, e.g., 'Magnum Bonum' and 'Lenape,' have been withdrawn from commercial sales due to excessive SGA levels during some cultivation years. However, these sudden SGA increases are diffucult to predict, and their causes are not understood. To identify external and genetic factors that underlie sudden SGA increases in certain potato cultivars, we have here in a 2-year study investigated 'Magnum Bonum' and five additional table potato cultivars for their SGA levels after wounding and light exposure.

Results and methods: Results showed that 'Magnum Bonum' has an unusual strong SGA response to light exposure, but not to wounding, whereas 'Bintje' displayed an opposite regulation. Levels of calystegine alkaloids were not significantly altered by treatments, implicating independent metabolic regulation of SGA and calystegine levels also under conditions of high SGA accumulation. Metabolomic and transcriptomic analyses identified a small number of key genes whose expression correlated with SGA differences between cultivars. Overexpression of two key genes in transgenic low-SGA potato cultivars increased their leaf SGA levels significantly.

Discussion: The results show that a strong response to light can underlie the SGA peaks that occasionally occur in certain potato cultivars and indicate that a between-cultivar variation in the expression of single SGA key genes can account for cultivar SGA differerences. We propose that current attempts to mitigate the SGA hazard will benefit from an increased consideration of cultivar-dependent SGA responses to post-harvest conditions, particularly light exposure. The identified key SGA genes can now be used as a molecular tool in this work.

Keywords: abiotic stress; calystegines; glycoalkaloids; metabolomics; potato (Solanum tuberosum L.); solanine; transcriptomics.

Grants and funding

This research was supported by METROFOOD-CZ research infrastructure project (MEYS Grant no. LM2023064 and specific university research Grant no. A1_FPBT_2023_002) and Stiftelsen Olle Engkvist Byggmästare (no. 2012/403).