Metabolite profiling of Ricinus communis germination at different temperatures provides new insights into thermo-mediatedrequirements for successful seedling establishment

Ricinus communis seeds germinate to a high percentage and faster at 35¿C than at lower temperatures, butwith compromised seedling establishment. However, seedlings are able to cope with high temperaturesat later stages of seedling establishment if germination occurred at lower temperatures. Our objectivewas to assess the biochemical and molecular requirements of R. communis germination for successfulseedling establishment at varying temperatures. For that, we performed metabolite profiling (GC-TOF-MS) and measured transcript levels of key genes involved in several energy-generating pathways, such asstorage oil mobilization, -oxidation and gluconeogenesis of seeds germinated at three different temper-atures. We identified a thermo-sensitive window during seed germination in which high temperaturescompromise seedling development, most likely by down-regulating some energy-generating pathways.Overexpression of malate synthase (MLS) and glycerol kinase (GK) genes resulted in higher starch levelsin Nicotiana benthamiana leaves, which highlights the importance of these genes in energy-generatingpathways for seedling establishment. Additionally, we showed that GABA, which is a stress-responsivemetabolite, accumulated in response to the water content of the seeds during the initial phase of imbibi-tion. Herewith, we provide new insights into the molecular requirements for vigorous seedling growthof R. communis under different environmental conditions.