Abstract

The plant circadian system consists of a network of input signals, output rhythms and a molecular clock, which interact to create a robust oscillator. This oscillator fine tunes biological processes to maximise plant fitness, and is therefore of great interest to modify to create stress tolerant crops. Previous work has shown that circadian oscillations of cytosolic calcium form both an output and an input into the oscillator, and are inhibited by the small metabolite nicotinamide. This is likely to be due to inhibition of an ADP -ribosyl cyclase, which produces the calcium mobilising agent cyclic adenosine diphosphoribose (cADPR). Nicotinamide has also been shown to inhibit poly-ADP ribose polymerases (PARPs), and Sirtuins, a class of NAD -dependent histone deacetlyases. In addition to abolition of calcium oscillations nicotinamide causes a period lengthening effect on other circadian outputs. In this talk I will discuss the forward genetics approach being taken to discover novel components in this pathway, and the screening tools that we have developed to identify mutants with an altered response to nicotinamide.