title: NAD⁺ accumulation as a metabolic off switch for orthodox pollen.
abstract: Terrestrial plant pollen is classified into two categories based on its metabolic status: pollen with low-metabolism are termed "orthodox" and pollen with high-metabolism are termed "recalcitrant." Nicotinamide adenine dinucleotide (NAD) is crucial for a number of metabolisms in all extant organisms. It has recently been shown that NAD homeostasis plays an important role in a broad range of developmental processes and responses to environment. Recently, a reverse genetic approach shed light on the significance of NAD biosynthesis on pollen fate. In orthodox Arabidopsis pollen, NAD(+) that was accumulated in excess at dispersal dramatically decreased on rehydration. The lack of a key gene that is involved in NAD biosynthesis compromised the excess accumulation. Moreover, absence of the excess accumulation phenocopied the so-called recalcitrant pollen, as demonstrated by the germination inside anthers and the loss of desiccation tolerance. Upon rehydration, NAD(+)-consuming inhibitors impaired tube germination. Taken together, our results suggest that accumulation of NAD(+) functions as a physiochemical molecular switch for suspended metabolism and that the decrease of NAD(+) plays a very important role during transitions in metabolic states. Shifting of the redox state to an oxidizing environment may efficiently control the comprehensive metabolic network underlying the onset of pollen germination.
authors: Environmental Science Research Laboratory; Central Research Institute of Electric Power Industry (CRIEPI); Abiko-shi Chiba, Japan.
authors: Shin-Nosuke
authors: SN
authors: Hashida
authors: Maki
authors: M
authors: Kawai-Yamada
authors: Hirofumi
authors: H
authors: Uchimiya
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D006706:Homeostasis; D009243:NAD / Q000378:metabolism*; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000378:metabolism; D010084:Oxidation-Reduction; D011058:Pollen / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D009243:NAD; D009612:Nicotinamide-Nucleotide Adenylyltransferase
keywords: NAD biosynthesis; NAD homeostasis; germination; nicotinamide adenine dinucleotide (NAD); pollen; redox