Nucleoid-enriched proteomes in developing plastids and chloroplasts from maize leaves: a new conceptual framework for...

Area of Science:

• Plant Biology
• Molecular Biology
• Organelle Biology

Background:

• Plastids contain multiple DNA copies organized into nucleoids.
• The precise roles of nucleoids in plastid gene expression and DNA management are unclear.

Purpose of the Study:

• To characterize the proteome of maize plastid nucleoids.
• To understand the factors involved in plastid DNA organization, repair, and replication.
• To provide a framework for nucleoid function in gene expression.

Main Methods:

• Isolation of highly enriched nucleoid fractions from maize proplastids and chloroplasts.
• Mass spectrometry-based proteomic analysis.
• Quantitative comparison with unfractionated plastid proteomes.

Main Results:

• Identified nucleoid-enriched proteins involved in DNA replication, organization, repair, transcription, mRNA processing, splicing, and editing.
• Discovered significant enrichment of 70S ribosomes and assembly factors, but not chaperones.
• Found that mRNA processing, splicing, editing, and ribosome assembly likely occur cotranscriptionally at the nucleoid.
• Observed a shift in nucleoid function from RNA metabolism in proplastids to translation and homeostasis in chloroplasts.

Conclusions:

• Maize plastid nucleoids are dynamic structures involved in DNA and RNA metabolism, as well as translation.
• Cotranscriptional processes are likely prevalent within plastid nucleoids.
• The study expands the known maize plastid proteome, offering a resource for future research.