title: The Arabidopsis FLAKY POLLEN1 gene encodes a 3-hydroxy-3-methylglutaryl-coenzyme A synthase required for development of tapetum-specific organelles and fertility of pollen grains.
abstract: The pollen coat is a surface component of pollen grains required for fertilization. To study how the pollen coat is produced, we identified and characterized a recessive and conditional male-sterile Arabidopsis mutant, flaky pollen1-1 (fkp1-1), whose pollen grains lack functional pollen coats. FKP1 is a single-copy gene in the Arabidopsis genome and encodes 3-hydroxy-3-methylglutaryl-coenzyme A synthase (HMG-CoA synthase), an enzyme of the mevalonate (MVA) pathway involved in biosynthesis of isoprenoids such as sterols. We found that fkp1-1 possesses a T-DNA insertion 550 bp upstream of the initiation codon. RT-PCR and promoter analyses revealed that fkp1-1 results in knockdown of FKP1 predominantly in tapetum. Electron microscopy showed that the mutation affected the development of tapetum-specific lipid-containing organelles (elaioplast and tapetosome), causing the deficient formation of fkp1-1 pollen coats. These results suggest that both elaioplasts, which accumulate vast amount of sterol esters, and tapetosomes, which are unique oil-accumulating structures, require the MVA pathway for development. Null alleles of fkp1 were male-gametophyte lethal upon pollen tube elongation, whereas female gametophytes were normal. These results show that the MVA pathway is essential, at least in tapetal cells and pollen grains, for the development of tapetum-specific organelles and the fertility of pollen grains.
authors.affiliation: Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan. guronyan@agr.nagoya-u.ac.jp
authors.forename: Sumie
authors.initials: S
authors.lastname: Ishiguro
authors.forename: Yuka
authors.initials: Y
authors.lastname: Nishimori
authors.forename: Miho
authors.initials: M
authors.lastname: Yamada
authors.forename: Hiroko
authors.initials: H
authors.lastname: Saito
authors.forename: Toshiya
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyake
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Okada
authors.forename: Kenzo
authors.initials: K
authors.lastname: Nakamura
mesh_terms: D000214:Acyl Coenzyme A / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D017343:Genes, Plant; D046529:Microscopy, Electron, Transmission; D016254:Mutagenesis, Insertional; D009154:Mutation; D015388:Organelles / Q000201:enzymology / Q000648:ultrastructure; D051479:Plant Infertility; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D011058:Pollen / Q000201:enzymology / Q000235:genetics / Q000254:growth & development*; D011401:Promoter Regions, Genetic
chemical_list: D000214:Acyl Coenzyme A; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; C008047:3-hydroxy-3-methylglutaryl-coenzyme A