A bipartite molecular module controls cell death activation in the Basal cell lineage of plant embryos

PLoS Biol. 2013 Sep;11(9):e1001655. doi: 10.1371/journal.pbio.1001655. Epub 2013 Sep 10.

Abstract

Plant zygote divides asymmetrically into an apical cell that develops into the embryo proper and a basal cell that generates the suspensor, a vital organ functioning as a conduit of nutrients and growth factors to the embryo proper. After the suspensor has fulfilled its function, it is removed by programmed cell death (PCD) at the late stages of embryogenesis. The molecular trigger of this PCD is unknown. Here we use tobacco (Nicotiana tabacum) embryogenesis as a model system to demonstrate that the mechanism triggering suspensor PCD is based on the antagonistic action of two proteins: a protease inhibitor, cystatin NtCYS, and its target, cathepsin H-like protease NtCP14. NtCYS is expressed in the basal cell of the proembryo, where encoded cystatin binds to and inhibits NtCP14, thereby preventing precocious onset of PCD. The anti-cell death effect of NtCYS is transcriptionally regulated and is repressed at the 32-celled embryo stage, leading to increased NtCP14 activity and initiation of PCD. Silencing of NtCYS or overexpression of NtCP14 induces precocious cell death in the basal cell lineage causing embryonic arrest and seed abortion. Conversely, overexpression of NtCYS or silencing of NtCP14 leads to profound delay of suspensor PCD. Our results demonstrate that NtCYS-mediated inhibition of NtCP14 protease acts as a bipartite molecular module to control initiation of PCD in the basal cell lineage of plant embryos.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cathepsin H / metabolism*
  • Cell Death
  • Cell Lineage / genetics
  • Cystatins / biosynthesis
  • Cystatins / genetics
  • Cystatins / metabolism*
  • Gene Expression Regulation, Plant
  • Protein Binding
  • Seeds / embryology*
  • Seeds / genetics
  • Seeds / metabolism
  • Sequence Alignment
  • Tobacco / embryology*
  • Tobacco / metabolism

Substances

  • Cystatins
  • Cathepsin H

Grant support

This work was supported by project (2014CB943400), National Natural Science Fund of China (31170297; 31270362; 31070284), China Postdoctoral Science Foundation funded project (2012M521460), the Swedish Research Council (VR) and Knut and Alice Wallenberg Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.