title: A novel group of oleosins is present inside the pollen of Arabidopsis.
abstract: In plants, subcellular triacylglycerol granules in seeds (oil bodies) and floral tapetum (tapetosomes) are stabilized by amphipathic structural protein called oleosin. We hereby report a novel group of oleosins that is present inside the pollen of Arabidopsis thaliana. We have used the conserved sequence of oleosins to locate, via the DNA database, all 16 oleosin genes in the Arabidopsis genome. The oleosin genes can be divided into three groups according to their sequences and tissue-specific expressions, as probed by RNA blot hybridization and reverse transcriptase-PCR. The first group includes eight genes specifically expressed in the floret tapetum. The second group includes five genes specifically expressed in maturing seeds. The third, novel group includes three genes expressed in both maturing seeds and floral microspores, which will become pollen. Transgenic study using the promoter of one of these genes attached to a reporter gene has provided corroborative evidence for the specific expression of the gene in the microspores in the florets. One of the pollen oleosins can be identified by microsequencing and specific immunoblotting. Pollen oleosins synthesized by recombinant bacteria can collaborate with phospholipids in stabilizing reconstituted oil bodies. Thus, pollen has oleosins to stabilize the abundant subcellular oil bodies. Seed oil bodies and floret tapetosomes have been isolated from the miniature Arabidopsis plants, and the success indicates that the organelles can be subjected to future biochemical and genetic studies.
authors.affiliation: Center for Plant Cell Biology, Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
authors.forename: Hyun Uk
authors.initials: HU
authors.lastname: Kim
authors.forename: Kai
authors.initials: K
authors.lastname: Hsieh
authors.forename: Chandra
authors.initials: C
authors.lastname: Ratnayake
authors.forename: Anthony H C
authors.initials: AH
authors.lastname: Huang
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000378:metabolism*; D029681:Arabidopsis Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011058:Pollen / Q000737:chemistry; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; C079353:oleosin protein, Arabidopsis; D012313:RNA