Stromal Protein Chloroplast Development and Biogenesis1 Is Essential for Chloroplast Development and Biogenesis in Arabidopsis thaliana.

Weijie Chen,Shiwei Chen,Lianwei Peng,Lin Zhang,Qiang Xin,Jingang Huang,Jean-David Rochaix

doi:10.3389/fpls.2022.815859

Weijie Chen, Shiwei Chen + Show 5 more

Open Access

https://doi.org/10.3389/fpls.2022.815859

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Abstract

Although numerous studies have been carried out on chloroplast development and biogenesis, the underlying regulatory mechanisms are still largely elusive. Here, we characterized a chloroplast stromal protein Chloroplast Development and Biogenesis1 (CDB1). The knockout cdb1 mutant exhibits a seedling-lethal and ivory leaf phenotype. Immunoblot and RNA blot analyses show that accumulation of chloroplast ribosomes is compromised in cdb1, resulting in an almost complete loss of plastid-encoded proteins including the core subunits of the plastid-encoded RNA polymerase (PEP) RpoB and RpoC2, and therefore in impaired PEP activity. Orthologs of CDB1 are found in green algae and land plants. Moreover, a protein shows high similarity with CDB1, designated as CDB1-Like (CDB1L), is present in angiosperms. Absence of CDB1L results in impaired embryo development. While CDB1 is specifically located in the chloroplast stroma, CDB1L is localized in both chloroplasts and mitochondria in Arabidopsis. Thus, our results demonstrate that CDB1 is indispensable for chloroplast development and biogenesis through its involvement in chloroplast ribosome assembly whereas CDB1L may fulfill a similar function in both mitochondria and chloroplasts.

Highlights

Chloroplasts are the sites of photosynthesis in eukaryotic cells and arose from a cyanobacteriumlike ancestor through endosymbiosis
Chloroplast Development and Biogenesis1 (CDB1) was absent in the cdb1 mutant due to the T-DNA insertion in AT4G37920. These results indicate that cdb1 is a null mutation and CDB1 is responsible for chlorophyll accumulation and chloroplast development
To address the possible role of CDB1 in chloroplast ribosome accumulation, we examined the levels of chloroplast ribosomal proteins and rRNA in cdb1 and WT

Summary

Introduction

Chloroplasts are the sites of photosynthesis in eukaryotic cells and arose from a cyanobacteriumlike ancestor through endosymbiosis. Chloroplasts transcribe their own genome into mRNAs for protein synthesis. These proteins are essential for the development of functional chloroplasts (Sakamoto et al, 2008). Chloroplast genomes of green plants comprise ~120 genes encoding the components of the gene expression system (RNA polymerase core subunits, ribosomal proteins, tRNAs, and rRNAs), subunits of the photosynthetic machinery [Rubisco, CDB1 Facilitates Chloroplast Biogenesis photosystem I and II (PSI and PSII), cytochrome b6f complex (Cyt b6f), ATP synthase, and NAD(P)H dehydrogenase-like (NDH) complex] as well as some other proteins involved in various metabolic processes in chloroplasts (Dobrogojski et al, 2020). Chloroplast development and biogenesis require tight coordination of plastid and nuclear gene expression

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