An in vitro control mechanism for potato stress metabolite biosynthesis

Ethylene/oxygen ($\text{E/O}_{2}$) elevates sesquiterpenoid stress metabolite (SSM) levels in potato (Solanum tuberosum L.) tuber tissue which is reacting hypersensitively. To determine whether $\text{E/O}_{2}$ retards SSM turnover, a measured amount of rishitin was applied to tuber tissue which was then incubated in air or $\text{E/O}_{2}$, and rishitin disappearance was monitored. No difference in the rate of rishitin disappearance was detected between air and $\text{E/O}_{2}$ incubations. However, tissue treated with rishitin and incubated in $\text{E/O}_{2}$ accumulated intermediates of the katahdinone and phytuberin pathways. This was not the case in rishitin-air treatments. These results suggest the dual involvement of ethylene and SSM intermediates in the regulation of the biosynthesis of SSM, compounds which may serve as phytoalexins.