A Ploidy-Sensitive Mechanism Regulates Aperture Formation on the Arabidopsis Pollen Surface and Guides Localization of the Aperture Factor INP1

PLoS Genet. 2016 May 13;12(5):e1006060. doi: 10.1371/journal.pgen.1006060. eCollection 2016 May.

Abstract

Pollen presents a powerful model for studying mechanisms of precise formation and deposition of extracellular structures. Deposition of the pollen wall exine leads to the generation of species-specific patterns on pollen surface. In most species, exine does not develop uniformly across the pollen surface, resulting in the formation of apertures-openings in the exine that are species-specific in number, morphology and location. A long time ago, it was proposed that number and positions of apertures might be determined by the geometry of tetrads of microspores-the precursors of pollen grains arising via meiotic cytokinesis, and by the number of last-contact points between sister microspores. We have tested this model by characterizing Arabidopsis mutants with ectopic apertures and/or abnormal geometry of meiotic products. Here we demonstrate that contact points per se do not act as aperture number determinants and that a correct geometric conformation of a tetrad is neither necessary nor sufficient to generate a correct number of apertures. A mechanism sensitive to pollen ploidy, however, is very important for aperture number and positions and for guiding the aperture factor INP1 to future aperture sites. In the mutants with ectopic apertures, the number and positions of INP1 localization sites change depending on ploidy or ploidy-related cell size and not on INP1 levels, suggesting that sites for aperture formation are specified before INP1 is brought to them.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics*
  • Cell Wall / genetics
  • Cytokinesis / genetics
  • Meiosis / genetics
  • Mutant Proteins / genetics
  • Ploidies*
  • Pollen / genetics*
  • Pollen / growth & development
  • Species Specificity

Substances

  • Arabidopsis Proteins
  • INP1 protein, Arabidopsis
  • Mutant Proteins

Grants and funding

Funding for this project was provided by the Department of Molecular Genetics and Center for Applied Plant Sciences at OSU and by the US National Science Foundation (MCB-1517511). RF is the recipient of undergraduate fellowships from the NSF-supported Pollen Research Coordination Network (MCB-0955910) and from the American Society of Plant Biologists (ASPB-SURF). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.