Forward and reverse genetic identification of mutants linking [Ca2+]cyt to the Arabidopsis thaliana circadian clock

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• Timothy Hearn
• Thursday 19 June 2014, 16:30-17:00
• Department of Plant Sciences, Large Lecture Theatre.

If you have a question about this talk, please contact Megan Cooper.

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 ([Ca2+]cyt) 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 diphosphate ribose (cADPR). Nicotinamide has also been shown to inhibit poly-ADP ribose polymerases (PARPs), and SIRTUI Ns, a class of NAD -dependent histone deacetlyases. In mammals both PARPS and SIRTUI Ns have been shown to regulate the amplitude of the circadian clock, whereas mutation of the mammalian ADP Rcyclase CD38 lengthens clock period. In addition to abolition of [Ca2+]cyt oscillations nicotinamide also causes both period lengthening and amplitude dampening of other circadian outputs in Arabidopsis. This period effect is thought to represent the role of [Ca2+]cyt in entraining the circadian clock. In this talk I will present the results from a forward genetic screen showing that we have been able to genetically dissect the period and amplitude effects of nicotinamide from one another. Further we find that only period mutants have disrupted circadian [Ca2+]cyt oscillations and cADPR mediated signalling. These results provide the first genetic tools for investigating the relationship between cADPR mediated [Ca2+]cyt signalling and the circadian clock.

This talk is part of the Plant Sciences Research Seminars series.

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