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Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants
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Genes encoding lipid II flippase MurJ and peptidoglycan hydrolases are required for chloroplast division in the moss

Hanae Utsunomiya1, Nozomi Saiki1, Hayato Kadoguchi2

  • 1Graduate School of Science and Technology, Kumamoto University, Kumamoto, 860-8555, Japan.

Plant Molecular Biology
|October 20, 2020
PubMed
Abstract

Insights

Homologous genes for peptidoglycan precursor flippase MurJ (murine norovirus J) and peptidoglycan hydrolases, including lytic transglycosylase MltB and DD-carboxypeptidase VanY, are essential for chloroplast division in the model moss Physcomitrella patens.

Area of Science:

  • Plant Biology
  • Cell Biology
  • Biochemistry

Background:

  • The moss Physcomitrella patens is a model organism for studying plastid biology.
  • Peptidoglycan biosynthesis and hydrolysis are crucial in bacteria for cell division.
  • The roles of bacterial peptidoglycan-related genes in plant cell division are largely unexplored.

Purpose of the Study:

  • To investigate the function of bacterial peptidoglycan-related homologs in chloroplast division in Physcomitrella patens.
  • To identify key genes involved in regulating chloroplast number and morphology.

Main Methods:

  • Genome-wide search for homologs of bacterial peptidoglycan biosynthesis and hydrolysis genes.
  • Gene knockout studies using CRISPR/Cas9.
  • Localization studies using GFP fusion proteins.
  • Chloroplast counting and morphological analysis.
  • Enzymatic activity assays for recombinant proteins.

Main Results:

  • Identified homologs for MurJ (PpMurJ), MltB (PpMltB), VanY (PpVanY), NagZ (PpNagZ), LdcA (PpLdcA), and a beta-lactamase-like gene (Pplactamase).
  • PpMltB and PpVanY proteins localize to chloroplasts, while others localize to the cytoplasm.
  • Disruption of PpMurJ leads to macrochloroplasts.
  • Knockout of PpMltB and PpVanY individually results in reduced chloroplast numbers.
  • PpMltB exhibits peptidoglycan hydrolase activity.

Conclusions:

  • PpMurJ, PpMltB, and PpVanY are critical for proper chloroplast division in Physcomitrella patens.
  • These genes, involved in peptidoglycan precursor transport and hydrolysis, play conserved roles in plant organelle division.
  • The findings provide insights into the evolution of cell division mechanisms across different domains of life.
Keywords:
Chloroplast divisionLipid II flippaseLytic transglycosylasePeptidasePhyscomitrella patens

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