Plant development. Arabidopsis NAC45/86 direct sieve element morphogenesis culminating in enucleation

Science. 2014 Aug 22;345(6199):933-7. doi: 10.1126/science.1253736. Epub 2014 Jul 31.


Photoassimilates such as sugars are transported through phloem sieve element cells in plants. Adapted for effective transport, sieve elements develop as enucleated living cells. We used electron microscope imaging and three-dimensional reconstruction to follow sieve element morphogenesis in Arabidopsis. We show that sieve element differentiation involves enucleation, in which the nuclear contents are released and degraded in the cytoplasm at the same time as other organelles are rearranged and the cytosol is degraded. These cellular reorganizations are orchestrated by the genetically redundant NAC domain-containing transcription factors, NAC45 and NAC86 (NAC45/86). Among the NAC45/86 targets, we identified a family of genes required for enucleation that encode proteins with nuclease domains. Thus, sieve elements differentiate through a specialized autolysis mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / ultrastructure
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / physiology*
  • Cell Nucleus / metabolism*
  • Cell Nucleus / ultrastructure
  • Gene Expression Regulation, Developmental
  • Gene Expression Regulation, Plant
  • Imaging, Three-Dimensional
  • Microscopy, Electron
  • Morphogenesis / genetics
  • Morphogenesis / physiology*
  • Phloem / growth & development*
  • Phloem / ultrastructure
  • Transcription Factors / genetics
  • Transcription Factors / physiology*


  • Arabidopsis Proteins
  • Transcription Factors