title: A gain-of-function mutation of Arabidopsis lipid transfer protein 5 disturbs pollen tube tip growth and fertilization.
abstract: During compatible pollination of the angiosperms, pollen tubes grow in the pistil transmitting tract (TT) and are guided to the ovule for fertilization. Lily (Lilium longiflorum) stigma/style Cys-rich adhesin (SCA), a plant lipid transfer protein (LTP), is a small, secreted peptide involved in pollen tube adhesion-mediated guidance. Here, we used a reverse genetic approach to study biological roles of Arabidopsis thaliana LTP5, a SCA-like LTP. The T-DNA insertional gain-of-function mutant plant for LTP5 (ltp5-1) exhibited ballooned pollen tubes, delayed pollen tube growth, and decreased numbers of fertilized eggs. Our reciprocal cross-pollination study revealed that ltp5-1 results in both male and female partial sterility. RT-PCR and beta-glucuronidase analyses showed that LTP5 is present in pollen and the pistil TT in low levels. Pollen-targeted overexpression of either ltp5-1 or wild-type LTP5 resulted in defects in polar tip growth of pollen tubes and thereby decreased seed set, suggesting that mutant ltp5-1 acts as a dominant-active form of wild-type LTP5 in pollen tube growth. The ltp5-1 protein has additional hydrophobic C-terminal sequences, compared with LTP5. In our structural homology/molecular dynamics modeling, Tyr-91 in ltp5-1, replacing Val-91 in LTP5, was predicted to interact with Arg-45 and Tyr-81, which are known to interact with a lipid ligand in maize (Zea mays) LTP. Thus, Arabidopsis LTP5 plays a significant role in reproduction.
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
authors.forename: Keun
authors.initials: K
authors.lastname: Chae
authors.forename: Chris A
authors.initials: CA
authors.lastname: Kieslich
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Morikis
authors.forename: Seung-Chul
authors.initials: SC
authors.lastname: Kim
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Lord
mesh_terms: D000595:Amino Acid Sequence; D052179:Antigens, Plant / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D005306:Fertilization / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D010802:Phylogeny; D051479:Plant Infertility / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D053205:Pollen Tube / Q000254:growth & development*; D017434:Protein Structure, Tertiary; D018749:RNA, Plant / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D052179:Antigens, Plant; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D010940:Plant Proteins; D018749:RNA, Plant; C036483:T-DNA; C511920:lipid transfer proteins, plant