Physical changes in the environment of plants often cause physiological and biochemical changes in the plant. For example, some important crop plants such as sorghum produce cyanogenic glucosides during drought, which leaves farmers with a dilemma: During periods of drought when animals need food the most, farmers are often forced to discard their sorghum harvest because they risk poisoning their animals with cyanide by using it as feed. This subproject aims to elucidate plants' plasticity to abiotic changes in the environment.
Studies in cassava leaves have indicated a strong fluctuation in the content of cyanogenic glucosides following a diurnal rhythm. This suggests the operation of an endogenous route by which the cyanogenic glucosides are turned over and constantly re-synthesized to balance primary metabolism. Two key regulatory networks mediate diurnal rhythm via light signalling: Transcriptional regulation and post-translational regulation. However, detailed knowledge on the component operating in the signaling network between the light impulse and the biosynthesis of specialized metabolites such as cyanogenic glucosides in plants is rudimentary.
To advance our knowledge of light signaling-dependent regulatory networks on the biosynthesis of cyanogenic glucosides we are studying these reactions at the transcriptional level using the cytochrome P450s in cassava as our experimental system. We are also investigating the possible role of post-translational regulation on the activities of the cytochrome P450 enzymes as well as the role of Ub E3 ligases, regulators in protein degradation. Through these studies, we expect to unveil the hidden layer of regulatory networks for cytochrome P450s and cyanogenic glucoside biosynthesis, and to provide the first detailed evidence of how light signaling integrates into a specialized metabolic pathway.