title: Rab11 GTPase-regulated membrane trafficking is crucial for tip-focused pollen tube growth in tobacco.
abstract: Pollen tube growth is a polarized growth process whereby the tip-growing tubes elongate within the female reproductive tissues to deliver sperm cells to the ovules for fertilization. Efficient and regulated membrane trafficking activity incorporates membrane and deposits cell wall molecules at the tube apex and is believed to underlie rapid and focused growth at the pollen tube tip. Rab GTPases, key regulators of membrane trafficking, are candidates for important roles in regulating pollen tube growth. We show that a green fluorescent protein-tagged Nicotiana tabacum pollen-expressed Rab11b is localized predominantly to an inverted cone-shaped region in the pollen tube tip that is almost exclusively occupied by transport vesicles. Altering Rab11 activity by expressing either a constitutive active or a dominant negative variant of Rab11b in pollen resulted in reduced tube growth rate, meandering pollen tubes, and reduced male fertility. These mutant GTPases also inhibited targeting of exocytic and recycled vesicles to the pollen tube inverted cone region and compromised the delivery of secretory and cell wall proteins to the extracellular matrix. Properly regulated Rab11 GTPase activity is therefore essential for tip-focused membrane trafficking and growth at the pollen tube apex and is pivotal to reproductive success.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Massachusetts, Lederle Graduate Research Center, Amherst, Massachusetts 01003, USA.
authors.forename: Barend H J
authors.initials: BH
authors.lastname: de Graaf
authors.forename: Alice Y
authors.initials: AY
authors.lastname: Cheung
authors.forename: Tatyana
authors.initials: T
authors.lastname: Andreyeva
authors.forename: Kathryn
authors.initials: K
authors.lastname: Levasseur
authors.forename: Marcia
authors.initials: M
authors.lastname: Kieliszewski
authors.forename: Hen-ming
authors.initials: HM
authors.lastname: Wu
mesh_terms: D000199:Actins / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology; D035264:Flowers / Q000254:growth & development*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology* / Q000201:enzymology* / Q000502:physiology; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000199:Actins; D008565:Membrane Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins