As the most common RNA cap in eukaryotes, the 7-methylguanosine (m7G) cap impacts nearly all processes that a messenger RNA undergoes, such as splicing, polyadenylation, nuclear export, translation, and degradation. The metabolite and redox agent, nicotinamide adenine diphosphate (NAD+), can be used as an initiating nucleotide in RNA synthesis to result in NAD+-capped RNAs. Such RNAs have been identified in bacteria, yeast, and human cells, but it is not known whether they exist in plant transcriptomes. The functions of the NAD+ cap in RNA metabolism or translation are still poorly understood. Here, through NAD captureSeq, we show that NAD+-capped RNAs are widespread in Arabidopsis thaliana. NAD+-capped RNAs are predominantly messenger RNAs encoded by the nuclear and mitochondrial genomes, but not the chloroplast genome. NAD+-capped transcripts from the nuclear genome appear to be spliced and polyadenylated. Furthermore, although NAD+-capped transcripts constitute a small proportion of the total transcript pool from any gene, they are enriched in the polysomal fraction and associate with translating ribosomes. Our findings implicate the existence of as yet unknown mechanisms whereby the RNA NAD+ cap interfaces with RNA metabolic processes as well as translation initiation. More importantly, our findings suggest that cellular metabolic and/or redox states may influence, or be regulated by, mRNA NAD+ capping.

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Admicellar polymerizations were conducted in aqueous solutions to form electrically conducting poly(pyrrole) (PPy) ultrathin films on mica and graphite. Separate solutions were used for monomer adsolubilization and polymerization, so that at the start of the reaction step, the only monomer in solution was localized at the solid−liquid interface. Film morphology and thickness were examined using contact mode and noncontact mode atomic force microscopy and compared to previous results where oxidant was added to the adsorbing solution. PPy films formed on graphite from water or surfactant solutions were mainly composed of interlinked islands and disks (small and thin islands) at high density. On the other hand, PPy deposited on mica in water alone formed randomly scattered islands without any continuous film formation, while PPy from surfactant solutions formed the same type of films with islands and disks. The thickness of the well-connected films could be made less than 5 nm depending on reaction conditions and initial monomer concentration in the adsorbing solutions. The thicknesses are approximately an order of magnitude thinner than in the previous work where the adsorbing and reacting solutions were not separate, due to the change in the amount of monomer available for polymerization. Because the amount of monomer available for polymerization in this study is on the same order of magnitude as the amount of available monomer for admicellar polymerizations on high surface area particulates, this study probably better represents film thicknesses that occur in particulate systems as well.