Sorghum - Metabolism of dhurrin
Sorghum is a tropical grass with a very high content of the cyanogenic glucoside dhurrin. It is extremely drought tolerant and is an important fodder crop in especially Australia. However, the dhurrin level can reach levels that are toxic to cattle and there is therefore extensive interest in understanding factors that influence cyanogenesis in sorghum and in breeding less toxic cultivars.
Sorghum is also the plant in which the biosynthetic pathway responsible for production of cyanogenic glucosides was first identified, and it serves as an important model plant for our studies of the compounds.
Currently, our research focuses on the hypothesis that cyanogenic glucosides can serve as nitrogen storage for the plant. We know that young sorghum plants will accumulate extremely high amounts of dhurrin during the first few weeks after germination, until suddenly it drops to a non-toxic level within another few weeks. Something similar happens in the seed during maturation.
Our hypothesis is that the "disappearing" dhurrin is degraded via an alternative pathway not involving release of hydrogen cyanide. This endogenous turnover pathway allows the plant to recycle the nitrogen bound in dhurrin without the risk of toxic effects from hydrogen cyanide released inside the cells.
The sorghum endogenous turnover project is part of a project funded by FTP. This is a 5-year project for investigating several plants (mainly sorghum, barley and almonds) which seem to have evolved to utilize cyanogenic glucosides for other things than defense.