Global climate change and growing human population threaten agricultural productivity and food security, emphasizing the need of crop diversification with climate resilient and nutritious crops. Chenopodium quinoa has gained attention due to its stress adaptability and nutritional value. Despite its resistance to cold, drought, and salinity, quinoa remains heat susceptible. Furthermore, while quinoa seeds are gluten-free and nutrient-rich, they contain bitter-tasting saponins (e.g. oleanolic acid), which limit their usage. Thus, understanding the mechanisms underlying quinoa's heat sensitivity and saponin biosynthesis is crucial for its sustainable cultivation and wider adoption.
Firstly, we investigated the impact of daytime and night-time heating on quinoa. We found that reproductive stages are particularly heat sensitive, and night-time heating exacerbates the effects. The mechanistic basis of these observations is that daytime and night-time heating triggers asymmetric effects on CO2 assimilation and evolution pathways confirmed by physiological, gene expression and metabolite analyses. Thus, we unravel the regulatory networks underlying heat responses in C. quinoa, which is crucial to develop thermotolerant quinoa varieties.
Secondly, we discovered a novel cytochrome P450 (CYP) enzyme responsible for converting beta-amyrin into oleanolic acid. Functional validation through transient overexpression, virus-induced gene silencing (VIGS), heterologous expression experiments, coupled with UPLC-MS quantification of metabolites provide crucial insights into saponin biosynthesis pathways. These findings lay groundwork for developing saponin-free quinoa varieties, thereby enhancing its nutritional value for wider consumption.
In summary, our research addresses two critical challenges associated with quinoa i.e. heat sensitivity and bitterness due to saponin content. By unraveling underlying mechanisms and identifying key genes, we contribute to advancing quinoa breeding programs.
