Saponin determination, expression analysis and functional characterization of saponin biosynthetic genes in Chenopodium quinoa leaves.

Jennifer Fiallos-Jurado, Jacob Pollier, Tessa Moses, Philipp Arendt, Noelia Barriga-Medina, Eduardo Morillo, Venancio Arahana, Maria de Lourdes Torres, Alain Goossens, Antonio Leon-Reyes

Journal: Plant science : an international journal of experimental plant biology 2017;250():188-197

PMID: 27457995

Full Text on Elsevier Science View on PubMed

Abstract

Quinoa (Chenopodium quinoa Willd.) is a highly nutritious pseudocereal with an outstanding protein, vitamin, mineral and nutraceutical content. The leaves, flowers and seed coat of quinoa contain triterpenoid saponins, which impart bitterness to the grain and make them unpalatable without postharvest removal of the saponins. In this study, we quantified saponin content in quinoa leaves from Ecuadorian sweet and bitter genotypes and assessed the expression of saponin biosynthetic genes in leaf samples elicited with methyl jasmonate. We found saponin accumulation in leaves after MeJA treatment in both ecotypes tested. As no reference genes were available to perform qPCR in quinoa, we mined publicly available RNA-Seq data for orthologs of 22 genes known to be stably expressed in Arabidopsis thaliana using geNorm, NormFinder and BestKeeper algorithms. The quinoa ortholog of At2g28390 (Monensin Sensitivity 1, MON1) was stably expressed and chosen as a suitable reference gene for qPCR analysis. Candidate saponin biosynthesis genes were screened in the quinoa RNA-Seq data and subsequent functional characterization in yeast led to the identification of CqbAS1, CqCYP716A78 and CqCYP716A79. These genes were found to be induced by MeJA, suggesting this phytohormone might also modulate saponin biosynthesis in quinoa leaves. Knowledge of the saponin biosynthesis and its regulation in quinoa may aid the further development of sweet cultivars that do not require postharvest processing.

Address: Laboratorio de Biotecnología Agrícola y de Alimentos, Ingeniería en Agroempresas, Colegio de Ciencias e Ingenierías, Universidad San Francisco de Quito, Campus Cumbayá, 17-1200-841 Quito, Ecuador; Laboratorio de Biotecnología Vegetal, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Campus Cumbayá, 17-1200-841 Quito, Ecuador.; Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium.; Department of Plant Systems Biology, VIB, 9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Gent, Belgium; Inflammation Research Centre (IRC), VIB, 9052 Gent, Belgium; Department of Biochemistry and Microbiology, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.; Laboratorio de Biotecnología Agrícola y de Alimentos, Ingeniería en Agroempresas, Colegio de Ciencias e Ingenierías, Universidad San Francisco de Quito, Campus Cumbayá, 17-1200-841 Quito, Ecuador.; Instituto Nacional de Investigaciones Agropecuarias (INIAP), Estación Experimental Santa Catalina, Quito, Ecuador.; Laboratorio de Biotecnología Vegetal, Colegio de Ciencias Biológicas y Ambientales, Universidad San Francisco de Quito, Campus Cumbayá, 17-1200-841 Quito, Ecuador.; Laboratorio de Biotecnología Agrícola y de Alimentos, Ingeniería en Agroempresas, Colegio de Ciencias e Ingenierías, Universidad San Francisco de Quito, Campus Cumbayá, 17-1200-841 Quito, Ecuador. Electronic address: [email protected].

DOI: 10.1016/j.plantsci.2016.05.015

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MeSH Terms: Chenopodium quinoa, Gene Expression Regulation, Plant, Organ Specificity, Plant Proteins, Saponins