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Additional file 1. Workstation specification, software tools and flow of code execution.

Additional file 2. Additional figures.

CLEMENS APPRICH, DAPHNE DRAGONA, GEERT LOVINK, AND FLORIAN WÜST - CONVERSATION MODERATED BY KRISTOFFER GANSING On August 6, 2019, the curatorial advisors of the transmediale 2020 exhibition, ‘The Eternal Network’, gathered at the festival’s offices in Berlin for a conversation on the status of network culture and theory today. Starting from the question ‘What was the network?’, the conversation explored the multiple trajectories of networks within cybernetics, art and philosophy, also taking the limits of networks into account. This included a reconsideration of the role of alternative and critical networks in today’s widespread digitalization, with its data-centric platform economy and the techno-cultural changes wrought by artificial intelligence.

The net amounts of carotenoids accumulating in plant tissues are determined by the rates of biosynthesis and degradation. While biosynthesis is rate-limited by the activity of PHYTOENE SYNTHASE (PSY), carotenoid losses are caused by catabolic enzymatic and non-enzymatic degradation. We established a system based on non-green Arabidopsis callus which allowed investigating major determinants for high steady-state levels of β-carotene. Wild-type callus development was characterized by strong carotenoid degradation which was only marginally caused by the activity of carotenoid cleavage oxygenases. In contrast, carotenoid degradation occurred mostly non-enzymatically and selectively affected carotenoids in a molecule-dependent manner. Using carotenogenic pathway mutants, we found that linear carotenes such as phytoene, phytofluene and pro-lycopene resisted degradation and accumulated while β-carotene was highly susceptible towards degradation. Moderately increased pathway activity through PSY overexpression was compensated by degradation revealing no net increase in β-carotene. However, higher pathway activities outcompeted carotenoid degradation and efficiently increased steady-state β-carotene amounts to up to 500 μg g-1 dry mass. Furthermore, we identified oxidative β-carotene degradation products which correlated with pathway activities, yielding β-apocarotenals of different chain length and various apocarotene-dialdehydes. The latter included methylglyoxal and glyoxal as putative oxidative end products suggesting a potential recovery of carotenoid-derived carbon for primary metabolic pathways. Moreover, we investigated the site of β-carotene sequestration by co-localization experiments which revealed that β-carotene accumulated as intra-plastid crystals which was confirmed by electron microscopy with carotenoid-accumulating roots. The results are discussed in the context of using the non-green calli carotenoid assay system for approaches targeting high steady-state β-carotene levels prior to their application in crops.