We previously described the effects of the bioactive sugar 7-deoxy-sedoheptolose (7dSh) that was isolated from culture supernatant of Synechococcus elongatus. 7dSh inhibits the growth of various phototrophic organisms including species of cyanobacteria, as well as the model plant organism Arabidopsis thaliana. Untargeted metabolome analysis of 7dSh treated organisms showed a strong accumulation of 7-deoxy-D-arabino-heptulosonic acid 7-phosphate (DHAP) the substrate of the 3-dehydoquinate synthase (DHQS) a key enzyme of the shikimate pathway. This indicates that 7dSh inhibits the shikimate pathway, an assumption that was confirmed through inhibition assays with purified DHQS and 7dSh. These findings explained the herbicidal activity of 7dSh, since the shikimate pathway is essential for bacteria, fungi, and plants. Additional experiments were undertaken with the non-diazotrophic cyanobacterium Synechocystis sp. (Synechocystis). Synechocystis is well-studied for its ability to perform chlorosis, a survival mechanism under nitrogen starvation. During chlorosis, cells accumulate glycogen, disassemble their photosynthetic apparatus, and enter a dormant state until they encounter a nitrogen source. Upon addition of a nitrogen source, cells regreen in a short period of time, thereby consuming the previously accumulated glycogen. Here, we show that 7dSh inhibits the ability to carry out the chlorosis process as well as the recovery of freshly chlorotic cells in the dark, a process that strictly depends on efficient glycogen catabolism. Our current data suggest that 7dSh has an immediate effect on the carbon metabolism by inhibiting glycogen accumulation and consumption. Our findings imply an active inhibition of the carbon metabolism by 7dSh.

Brilisauer, K et al. (2019). Cyanobacterial antimetabolite 7-deoxy-sedoheptulose blocks the shikimate pathway to inhibit the growth of prototrophic organisms. Nature Communications, 10 (545).

Rapp, Johanna et al. (2021). "In Vivo Inhibition of the 3-Dehydroquinat Synthase by 7 Deoxysedoheptulose Depends on Promiscuous Uptake by Sugar Transporters in Cyanobacteria." Frontiers in Microbiology 12: 1720.