Annexin5 plays a vital role in Arabidopsis pollen development via Ca2+-dependent membrane trafficking

PLoS One. 2014 Jul 14;9(7):e102407. doi: 10.1371/journal.pone.0102407. eCollection 2014.

Abstract

The regulation of pollen development and pollen tube growth is a complicated biological process that is crucial for sexual reproduction in flowering plants. Annexins are widely distributed from protists to higher eukaryotes and play multiple roles in numerous cellular events by acting as a putative "linker" between Ca2+ signaling, the actin cytoskeleton and the membrane, which are required for pollen development and pollen tube growth. Our recent report suggested that downregulation of the function of Arabidopsis annexin 5 (Ann5) in transgenic Ann5-RNAi lines caused severely sterile pollen grains. However, little is known about the underlying mechanisms of the function of Ann5 in pollen. This study demonstrated that Ann5 associates with phospholipid membrane and this association is stimulated by Ca2+ in vitro. Brefeldin A (BFA) interferes with endomembrane trafficking and inhibits pollen germination and pollen tube growth. Both pollen germination and pollen tube growth of Ann5-overexpressing plants showed increased resistance to BFA treatment, and this effect was regulated by calcium. Overexpression of Ann5 promoted Ca2+-dependent cytoplasmic streaming in pollen tubes in vivo in response to BFA. Lactrunculin (LatB) significantly prohibited pollen germination and tube growth by binding with high affinity to monomeric actin and preferentially targeting dynamic actin filament arrays and preventing actin polymerization. Overexpression of Ann5 did not affect pollen germination or pollen tube growth in response to LatB compared with wild-type, although Ann5 interacts with actin filaments in a manner similar to some animal annexins. In addition, the sterile pollen phenotype could be only partially rescued by Ann5 mutants at Ca2+-binding sites when compared to the complete recovery by wild-type Ann5. These data demonstrated that Ann5 is involved in pollen development, germination and pollen tube growth through the promotion of endomembrane trafficking modulated by calcium. Our results provide reliable molecular mechanisms that underlie the function of Ann5 in pollen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Annexins / genetics
  • Annexins / metabolism
  • Annexins / physiology*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Biological Transport
  • Calcium Signaling
  • Cytoplasmic Streaming
  • Germination
  • Models, Molecular
  • Molecular Sequence Data
  • Plants, Genetically Modified / growth & development
  • Plants, Genetically Modified / metabolism
  • Pollen Tube / genetics
  • Pollen Tube / growth & development*
  • Pollen Tube / metabolism
  • Protein Structure, Tertiary
  • RNA Interference
  • Reproduction
  • Sequence Alignment

Substances

  • Annexins
  • Arabidopsis Proteins

Grants and funding

This work was supported by the National Basic Research Program (2014CB954200–03), the National Natural Science Foundation of China (30800079 and 31270326), the Program for New Century Excellent Talents in University (NCET-13– 0264), and the Natural Science Foundation for Distinguished Yong Scholars of Gansu Province (2013GS10064) to YX. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.