Arabidopsis sirtuins and poly(ADP‐ribose) polymerases regulate gene expression in the day but do not affect circadian rhythms

Abstract

Nicotinamide-adenine dinucleotide (NAD) is involved in redox homeostasis and acts as a substrate for NADases, including poly(ADP-ribose) polymerases (PARPs) that add poly(ADP-ribose) polymers to proteins and DNA, and sirtuins that deacetylate proteins.Nicotinamide, a by-product of NADases increases circadian period in both plants and animals. In mammals, the effect of nicotinamide on circadian period might be mediated by the PARPs and sirtuins because they directly bind to core circadian oscillator genes.We have investigated whether PARPs and sirtuins contribute to the regulation of the circadian oscillator in Arabidopsis. We found no evidence that PARPs and sirtuins regulate the circadian oscillator of Arabidopsis or are involved in the response to nicotinamide. RNA-seq analysis indicated that PARPs regulate the expression of only a few genes, including FLOWERING LOCUS C. However, we found profound effects of reduced sirtuin 1 expression on gene expression during the day but not at night, and an embryo lethal phenotype in knockouts. Our results demonstrate that PARPs and sirtuins are not associated with NAD regulation of the circadian oscillator and that sirtuin 1 is associated with daytime regulation of gene expression.

Layers of crosstalk between circadian regulation and environmental signalling in plants

“…In the mouse, mutants of the circadian oscillator component Bmal1 reduce the expression of the mitochondrial deacetylase sirtuin SIRT3. In plants, it seems that a sirtuin mutant alters the transcriptome extensively during the day 123 , and this is not restricted to transcripts encoding mitochondrial proteins. Finally, some circadian arrhythmic Arabidopsis mutants cause substantial changes in the concentrations of mitochondrial intermediates of the tricarboxylic acid cycle (TCA cycle), indicating that the nuclear-encoded circadian oscillator impacts mitochondrial metabolism 8 .…”