title: Ni(2+) effects on Nicotiana tabacum L. pollen germination and pollen tube growth.
abstract: To investigate the mechanisms of Ni(2+) effects on initiation and maintenance of polar cell growth, we used a well-studied model system-germination of angiosperm pollen grains. In liquid medium tobacco pollen grain forms a long tube, where the growth is restricted to the very tip. Ni(2+) did not prevent the formation of pollen tube initials, but inhibited their subsequent growth with IC(50) = 550 μM. 1 mM Ni(2+) completely blocked the polar growth, but all pollen grains remained viable, their respiration was slightly affected and ROS production did not increase. Addition of Ni(2+) after the onset of germination had a bidirectional effect on the tubes development: there was a considerable amount of extra-long tubes, which appeared to be rapidly growing, but the growth of many tubes was impaired. Studying the localization of possible targets of Ni(2+) influence, we found that they may occur both in the wall and in the cytoplasm, as confirmed by specific staining. Ni(2+) disturbed the segregation of transport vesicles in the tips of these tubes and significantly reduced the relative content of calcium in the aperture area of pollen grains, as measured by X-ray microanalysis. These factors are considered being critical for normal polar cell growth. Ni(2+) also causes the deposition of callose in the tips of the tube initials and the pollen tubes that had stopped their growth. We can assume that Ni(2+)-induced disruption of calcium homeostasis can lead to vesicle traffic impairment and abnormal callose deposition and, consequently, block the polar growth.
authors.affiliation: Department of Plant Physiology, School of Biology, Lomonosov Moscow State University, 119991, Moscow, Russia. pollen-ions@yandex.ru
authors.forename: Maria
authors.initials: M
authors.lastname: Breygina
authors.forename: Natalie
authors.initials: N
authors.lastname: Matveyeva
authors.forename: Svetlana
authors.initials: S
authors.lastname: Polevova
authors.forename: Natalie
authors.initials: N
authors.lastname: Meychik
authors.forename: Yulia
authors.initials: Y
authors.lastname: Nikolaeva
authors.forename: Anna
authors.initials: A
authors.lastname: Mamaeva
authors.forename: Igor
authors.initials: I
authors.lastname: Yermakov
mesh_terms: D002473:Cell Wall / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D018525:Germination / Q000187:drug effects*; D009532:Nickel / Q000494:pharmacology*; D011058:Pollen / Q000254:growth & development*; D053205:Pollen Tube / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*; D014026:Nicotiana / Q000187:drug effects* / Q000254:growth & development
chemical_list: D009532:Nickel