title: SB401, a pollen-specific protein from Solanum berthaultii, binds to and bundles microtubules and F-actin.
abstract: We characterize a novel, pollen-specific, microtubule-associated protein, SB401, found in Solanum berthaultii. This protein binds to and bundles taxol-stabilized microtubules and enhances tubulin polymerization in a concentration-dependent manner, particularly at lower temperatures. Electron microscopy revealed that the protein decorates the entire length of microtubules. Cross-linking and electrophoresis studies showed that SB401 protein forms dimers, and suggest that dimerization could account for bundling. Double immunofluorescent staining of pollen tubes of S. berthaultii showed that SB401 protein co-localized with cortical microtubule bundles. SB401 protein also binds to and bundles actin filaments, and could connect actin filaments to microtubules. SB401 protein had a much higher affinity for microtubules than for actin filaments. In the presence of both cytoskeletal elements, the protein preferentially bound microtubules to form bundles. These results demonstrate that SB401 protein may have important roles in organizing the cytoskeleton in pollen tubes.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100094, China.
authors.forename: Shuli
authors.initials: S
authors.lastname: Huang
authors.forename: Lifeng
authors.initials: L
authors.lastname: Jin
authors.forename: Jizhou
authors.initials: J
authors.lastname: Du
authors.forename: Hua
authors.initials: H
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhao
authors.forename: Guangshuo
authors.initials: G
authors.lastname: Ou
authors.forename: Guangming
authors.initials: G
authors.lastname: Ao
authors.forename: Ming
authors.initials: M
authors.lastname: Yuan
mesh_terms: D000199:Actins / Q000378:metabolism*; D001704:Biopolymers / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism*; D053205:Pollen Tube / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D032322:Solanum / Q000737:chemistry / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
chemical_list: D000199:Actins; D001704:Biopolymers; D010940:Plant Proteins; D011994:Recombinant Proteins; D014404:Tubulin