Arabidopsis thaliana nicotinate/nicotinamide mononucleotide adenyltransferase (AtNMNAT) is required for pollen tube growth.
While mammals and fungi possess nicotinate/nicotinamide mononucleotide adenyltransferase (NMNAT) isoforms, Arabidopsis thaliana only contains a single NMNAT gene, AtNMNAT (At5g55810). We analyzed the enzymatic activity of the AtNMNAT-encoded protein to determine the role of AtNMNAT in plant development. AtNMNAT catalyzed the synthesis of nicotinate adenine dinucleotide (NaAD) from nicotinate mononucleotide (NaMN) in the Preiss-Handler-dependent pathway, and of nicotinamide adenine dinucleotide (NAD) from nicotiamide mononucleotide (NMN) in the Preiss-Handler-independent pathway. Prominent AtNMNAT expression was detected in the male gametophyte. Moreover, AtNMNAT expression was spatio-temporally regulated during microspore development and pollen tube growth. Disruption of the AtNMNAT gene (atnmnat mutant) was characterized by a decrease in NAD content in pollen. Cytological examinations revealed that the atnmnat mutant was gametophytically impaired in in vivo and in vitro pollen tube growth. Our results suggest that metabolic fulfillment via the NAD pathway is indispensable for normal pollen growth and subsequent normal seed production.
Hashida
Shin-nosuke
SN
Institute of Molecular and Cellular Biosciences (IMCB), The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan. shashida@iam.u-tokyo.ac.jp
Takahashi
Hideyuki
H
Kawai-Yamada
Maki
M
Uchimiya
Hirofumi
H
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D009243:NAD / Q000378:metabolism; D009537:Nicotinamide Mononucleotide / Q000031:analogs & derivatives / Q000378:metabolism; D009612:Nicotinamide-Nucleotide Adenylyltransferase / Q000235:genetics / Q000378:metabolism*; D053205:Pollen Tube / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; D011993:Recombinant Fusion Proteins; D009243:NAD; D009537:Nicotinamide Mononucleotide; C002953:nicotinate mononucleotide; D009612:Nicotinamide-Nucleotide Adenylyltransferase