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 biproduct
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 thy 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 1expression 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.