SUN anchors pollen WIP-WIT complexes at the vegetative nuclear envelope and is necessary for pollen tube targeting and fertility

J Exp Bot. 2015 Dec;66(22):7299-307. doi: 10.1093/jxb/erv425. Epub 2015 Sep 25.

Abstract

LINC (linker of nucleoskeleton and cytoskeleton) complexes play an essential role in nuclear migration by connecting the nucleus to the cytoskeleton and/or motor proteins. Plant LINC complexes have recently been identified in Arabidopsis thaliana, with the inner nuclear membrane SUN and outer nuclear membrane WIP proteins comprising the first identified complex. A recent study identified a nuclear movement defect in Arabidopsis pollen vegetative nuclei linked to the outer nuclear envelope WIP and WIT proteins. However, the role that SUN proteins may play in pollen nuclear migration has yet to be addressed. To explore this question, a SUN2 lumenal domain that was targeted to the ER specifically in pollen was over-expressed. It is shown that the ER-targeted SUN2 lumenal domain was able to displace WIP and WIT proteins from the pollen vegetative nuclear envelope. Expression of this dominant-negative transgene led to impaired VN mobility, impaired pollen tube guidance, and defective pollen tube reception. The observed pollen defects are similar to phenotypes observed in a wip1-1 wip2-1 wip3-1 wit1-1 wit2-1 mutant. It is also shown that these defects were dependent on the KASH-binding function of the SUN2 lumenal domain. These data support a model where LINC complexes formed by SUN, WIP, and WIT at the VNE are responsible for VN migration and suggest an important function of SUN, WIP, and WIT in pollen tube guidance and reception.

Keywords: Arabidopsis; KASH; SUN; nuclear envelope; nuclear migration; plant fertilization; pollen tube ovular guidance; pollen tube reception; vegetative nucleus..

Publication types

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

MeSH terms

  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / metabolism
  • Fertility
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins / metabolism*
  • Microtubule-Associated Proteins / metabolism*
  • Nuclear Envelope / metabolism*
  • Nuclear Proteins / metabolism*
  • Pollen Tube / metabolism*

Substances

  • Arabidopsis Proteins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Microtubule-Associated Proteins
  • Nuclear Proteins
  • SUN1 protein, Arabidopsis
  • SUN2 protein, Arabidopsis
  • WIT1 protein, Arabidopsis
  • WIT2 protein, Arabidopsis
  • WPP1 protein, Arabidopsis
  • WPP2 protein, Arabidopsis