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Overcoming Hybridization Barriers by the Secretion of the Maize Pollen Tube Attractant ZmEA1 from Arabidopsis Ovules

2012; Elsevier BV; Volume: 22; Issue: 13 Linguagem: Inglês

10.1016/j.cub.2012.04.061

1879-0445

Mihaela L. Márton, Astrid Fastner, Susanne Uebler, Thomas Dresselhaus,

Plant and animal studies

A major goal of plant reproduction research is to understand and overcome hybridization barriers so that the gene pool of crop plants can be increased and improved upon. After successful pollen germination on a receptive stigma, the nonmotile sperm cells of flowering plants are transported via the pollen tube (PT) to the egg apparatus for the achievement of double fertilization. The PT path is controlled by various hybridization mechanisms probably involving a larger number of species-specific molecular interactions [1Lausser A. Kliwer I. Srilunchang K.O. Dresselhaus T. Sporophytic control of pollen tube growth and guidance in maize.J. Exp. Bot. 2010; 61: 673-682Crossref PubMed Scopus (58) Google Scholar, 2Dresselhaus T. Lausser A. Márton M.L. Using maize as a model to study pollen tube growth and guidance, cross-incompatibility and sperm delivery in grasses.Ann. Bot. (Lond.). 2011; 108: 727-737Crossref PubMed Scopus (56) Google Scholar]. The egg-apparatus-secreted polymorphic peptides ZmEA1 in maize [3Márton M.L. Cordts S. Broadhvest J. Dresselhaus T. Micropylar pollen tube guidance by Egg Apparatus 1 of maize.Science. 2005; 307: 573-576Crossref PubMed Scopus (246) Google Scholar] and LURE1 and LURE2 in Torenia fournieri [4Okuda S. Tsutsui H. Shiina K. Sprunck S. Takeuchi H. Yui R. Kasahara R.D. Hamamura Y. Mizukami A. Susaki D. et al.Defensin-like polypeptide LUREs are pollen tube attractants secreted from synergid cells.Nature. 2009; 458: 357-361Crossref PubMed Scopus (450) Google Scholar] as well as TcCRP1 in T. concolor [5Kanaoka M.M. Kawano N. Matsubara Y. Susaki D. Okuda S. Sasaki N. Higashiyama T. Identification and characterization of TcCRP1, a pollen tube attractant from Torenia concolor.Ann. Bot. (Lond.). 2011; 108: 739-747Crossref PubMed Scopus (56) Google Scholar] were shown to be required for micropylar PT guidance, the last step of the PT journey. We report here that ZmEA1 attracts maize PTs in vitro and arrests their growth at higher concentrations. Furthermore, it binds to the subapical region of maize PT tips in a species-preferential manner. To overcome hybridization barriers at the level of gametophytic PT guidance, we expressed ZmEA1 in Arabidopsis synergid cells. Secreted ZmEA1 enabled Arabidopsis ovules to guide maize PT in vitro in a species-preferential manner to the micropylar opening of the ovule. These results demonstrate that the egg-apparatus-controlled reproductive-isolation barrier of PT guidance can be overcome even between unrelated plant families.