Chloroplast nucleoids as a transformable network revealed by live imaging with a microfluidic device

Yoshitaka Kamimura,Yoshiki Nishimura,Yusuke Kobayashi,Hitomi Tanaka,Toshiharu Shikanai

doi:10.1038/s42003-018-0055-1

Yoshitaka Kamimura, Yoshiki Nishimura + Show 3 more

Open Access

https://doi.org/10.1038/s42003-018-0055-1

Copy DOI

Abstract

Chloroplast DNA is organized into DNA–protein conglomerates called chloroplast nucleoids, which are replicated, transcribed, and inherited. We applied live-imaging technology with a microfluidic device to examine the nature of chloroplast nucleoids in Chlamydomonas reinhardtii. We observed the dynamic and reversible dispersion of globular chloroplast nucleoids into a network structure in dividing chloroplasts. In the monokaryotic chloroplast (moc) mutant, in which chloroplast nucleoids are unequally distributed following chloroplast division due to a defect in MOC1, the early stages of chloroplast nucleoid formation occurred mainly in the proximal area. This suggests the chloroplast nucleoid transformable network consists of a highly compact core with proximal areas associated with cpDNA replication and nucleoid formation.

Highlights

Chloroplast DNA is organized into DNA–protein conglomerates called chloroplast nucleoids, which are replicated, transcribed, and inherited
We aimed to capture the live movements of chloroplast nucleoids during chloroplast division to elucidate their behaviors and structural nature, which revealed that cp nucleoids are interconnected transformable network consisting of a highly compact core and peripheral/interconnecting areas associated with replication hot spots
~80 chloroplast DNA (cpDNA) copies are organized into 5–10 chloroplast nucleoids (~1.5 μm) that can be clearly observed by fluorescence microscopy (Fig. 1)

Summary

Introduction

Chloroplast DNA is organized into DNA–protein conglomerates called chloroplast nucleoids, which are replicated, transcribed, and inherited. Extensive mass spectrometry-based analyses detected multiple nucleoidassociated proteins with multifaceted functions, including core structural proteins as well as proteins related to replication/DNA inheritance, transcription, RNA maturation, translation, and membrane scaffolding[6,7]. Despite their complex multimeric form, chloroplast nucleoids are not static structures. We aimed to capture the live movements of chloroplast nucleoids during chloroplast division to elucidate their behaviors and structural nature, which revealed that cp nucleoids are interconnected transformable network consisting of a highly compact core and peripheral/interconnecting areas associated with replication hot spots

Objectives

Methods

Results

Conclusion