In order to expand green bio-production systems to synthesize high-value compounds, these need not only to be produced in high amounts to meet demand but also stored without being auto-toxic to the production host.
In nature, certain plants can accumulate natural products in very high amounts without showing auto-toxicity or disturbances of cell homeostasis. This is the case of Sorghum bicolor which produces the defence compound dhurrin in amounts reaching 30% of the dry mass in etiolated seedlings. Evidence points out that dhurrin is synthesized at the endoplasmic reticulum by P450 enzymes possibly in mesophyll cells and subsequently stored in the cytosol of epidermal cells. Transport and storage mechanisms that allow dhurrin to be synthesized and stored in such amounts without causing osmotic imbalances remain to be identified. If dhurrin is stored in biocondensates, whether these are membrane-enclosed or membrane-less is unknown. Phase partitioning induced by proteins or Natural Deep Eutectic Solvents might play a role.
Experimental studies are presented to answer these questions and identify key players involved, including methods of cell type separation, bioimaging, proximity labelling, analytic chemistry, and proteomics. Studying how plants orchestrate the formation of biocondensates to store compounds in high amounts is essential to making green bio-production systems feasible.