Manipulation of Light Signal Transduction Factors as a Means of Modifying Steroidal Glycoalkaloids Accumulation in Tomato Leaves.

Cui-cui Wang,Da-qi Fu,Donald Grierson,Lan-huan Meng,Ying Gao

doi:10.3389/fpls.2018.00437

Cui-cui Wang, Da-qi Fu + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2018.00437

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Abstract

Steroidal glycoalkaloids (SGAs) are cholesterol-derived specialized metabolites produced by Solanaceous plant species. They contribute to pathogen defense but are considered as anti-nutritional compounds and toxic to humans. Although the genes involved in the SGA biosynthetic pathway have been successfully cloned and identified, transcription factors regulating this pathway are still poorly understood. We report that silencing tomato light signal transduction transcription factors ELONGATED HYPOCOTYL 5 (SlHY5) and PHYTOCHROME INTERACTING FACTOR3 (SlPIF3), by virus-induced gene silencing (VIGS), altered glycoalkaloids levels in tomato leaves compared to control plant. Electrophoretic mobility shift assay (EMSA) and Chromatin immunoprecipitation (ChIP) analysis confirmed that SlHY5 and SlPIF3 bind to the promoter of target genes of GLYCOALKALOID METABOLISM (GAME1, GAME4, GAME17), affecting the steady-state concentrations of transcripts coding for SGA pathway enzymes. The results indicate that light-signaling transcription factors HY5 and PIF3 regulate the abundance of SGAs by modulating the transcript levels of these GAME genes. This insight into the regulation of SGA biosynthesis can be used for manipulating the level of these metabolites in crops.

Highlights

Steroidal glycoalkaloids (SGAs) are nitrogen-containing compounds produced primarily by Liliaceous (Veratrum californicum) (Augustin et al, 2015) and Solanaceous species such as potato (Solanum tuberosum), tomato (Solanum lycopersicum), and eggplant (Solanum melongena) (Heftmann, 1983)
To investigate whether the biosynthesis of SGAs is regulated by light signaling, a virus-induced gene silencing (VIGS) approach was used to silence the signal transduction transcription factors ELONGATED HYPOCOTYL 5 (SlHY5) and SlPIF3 genes
Further investigation confirmed that VIGS-treated leaves showed a reduction in SlPDS, SlHY5, and SlPIF3 transcripts ranging from ∼78 to 85% in all three samples compared to leaves of TRV2-infected control plants (Figure 2B)

Summary

Introduction

Steroidal glycoalkaloids (SGAs) are nitrogen-containing compounds produced primarily by Liliaceous (Veratrum californicum) (Augustin et al, 2015) and Solanaceous species such as potato (Solanum tuberosum), tomato (Solanum lycopersicum), and eggplant (Solanum melongena) (Heftmann, 1983). SGAs are stored in all plant tissues, including roots, flowers, leaves, and fruits (Friedman and Dao, 1992; Friedman, 2006; Kozukue et al, 2008; Iijima et al, 2013). SGAs act as phytoanticipins, providing the plant with a pre-existing defense against a broad range of pathogens (Milner et al, 2011), some are considered as anti-nutritional substances in the diet due to their toxic effects (Roddick, 1996). SGAs can cause gastro-intestinal and neurological disorders, and may be lethal to humans when present at high concentrations (Roddick, 1989). The principal SGAs are α-tomatine and dehydrotomatine, while esculeosides are predominant in the red ripe fruits (Fujiwara et al, 2004; Moco et al, 2007; Yamanaka et al, 2009)

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