title: FIMBRIN1 is involved in lily pollen tube growth by stabilizing the actin fringe.
abstract: An actin fringe structure in the subapex plays an important role in pollen tube tip growth. However, the precise mechanism by which the actin fringe is generated and maintained remains largely unknown. Here, we cloned a 2606-bp full-length cDNA encoding a deduced 77-kD fimbrin-like protein from lily (Lilium longiflorum), named FIMBRIN1 (FIM1). Ll-FIM1 was preferentially expressed in pollen and concentrated at actin fringe in the subapical region, as well as in longitudinal actin-filament bundles in the shank of pollen tubes. Microinjection of Ll-FIM1 antibody into lily pollen tubes inhibited tip growth and disrupted the actin fringe. Furthermore, we verified the function of Ll-FIM1 in the fim5 mutant of its closest relative, Arabidopsis thaliana. Pollen tubes of fim5 mutants grew with a larger diameter in early stages but could recover into normal forms in later stages, despite significantly slower growth rates. The actin fringe of the fim5 mutants, however, was impaired during both early and late stages. Impressively, stable expression of fim5pro:GFP:Ll-FIM1 rescued the actin fringe and the growth rate of Arabidopsis fim5 pollen tubes. In vitro biochemical analysis showed that Ll-FIM1 could bundle actin filaments. Thus, our study has identified a fimbrin that may stabilize the actin fringe by cross-linking actin filaments into bundles, which is important for proper tip growth of lily pollen tubes.
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing 100875, People's Republic of China.
authors.forename: Hui
authors.initials: H
authors.lastname: Su
authors.forename: Jinsheng
authors.initials: J
authors.lastname: Zhu
authors.forename: Chao
authors.initials: C
authors.lastname: Cai
authors.forename: Weike
authors.initials: W
authors.lastname: Pei
authors.forename: Jiaojiao
authors.initials: J
authors.lastname: Wang
authors.forename: Huaijian
authors.initials: H
authors.lastname: Dong
authors.forename: Haiyun
authors.initials: H
authors.lastname: Ren
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D027762:Lilium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009928:Organ Specificity; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D053205:Pollen Tube / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins; D017422:Sequence Analysis, DNA
chemical_list: D000199:Actins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C026742:plastin