TY  - JOUR
A1  - Janowski, Marcin Andrzej
A1  - Zoschke, Reimo
A1  - Scharff, Lars B.
A1  - Jaime, Silvia Martinez
A1  - Ferrari, Camilla
A1  - Proost, Sebastian
A1  - Xiong, Jonathan Ng Wei
A1  - Omranian, Nooshin
A1  - Musialak-Lange, Magdalena
A1  - Nikoloski, Zoran
A1  - Graf, Alexander
A1  - Schoettler, Mark Aurel
A1  - Sampathkumar, Arun
A1  - Vaid, Neha
A1  - Mutwil, Marek
T1  - AtRsgA from Arabidopsis thaliana is important for maturation of the small subunit of the chloroplast ribosome
JF  - The plant journal
N2  - Plastid ribosomes are very similar in structure and function to the ribosomes of their bacterial ancestors. Since ribosome biogenesis is not thermodynamically favorable under biological conditions it requires the activity of many assembly factors. Here we have characterized a homolog of bacterial RsgA in Arabidopsis thaliana and show that it can complement the bacterial homolog. Functional characterization of a strong mutant in Arabidopsis revealed that the protein is essential for plant viability, while a weak mutant produced dwarf, chlorotic plants that incorporated immature pre-16S ribosomal RNA into translating ribosomes. Physiological analysis of the mutant plants revealed smaller, but more numerous, chloroplasts in the mesophyll cells, reduction of chlorophyll a and b, depletion of proplastids from the rib meristem and decreased photosynthetic electron transport rate and efficiency. Comparative RNA sequencing and proteomic analysis of the weak mutant and wild-type plants revealed that various biotic stress-related, transcriptional regulation and post-transcriptional modification pathways were repressed in the mutant. Intriguingly, while nuclear- and chloroplast-encoded photosynthesis-related proteins were less abundant in the mutant, the corresponding transcripts were increased, suggesting an elaborate compensatory mechanism, potentially via differentially active retrograde signaling pathways. To conclude, this study reveals a chloroplast ribosome assembly factor and outlines the transcriptomic and proteomic responses of the compensatory mechanism activated during decreased chloroplast function. Significance Statement AtRsgA is an assembly factor necessary for maturation of the small subunit of the chloroplast ribosome. Depletion of AtRsgA leads to dwarfed, chlorotic plants, a decrease of mature 16S rRNA and smaller, but more numerous, chloroplasts. Large-scale transcriptomic and proteomic analysis revealed that chloroplast-encoded and -targeted proteins were less abundant, while the corresponding transcripts were increased in the mutant. We analyze the transcriptional responses of several retrograde signaling pathways to suggest the mechanism underlying this compensatory response.
KW  - ribosome assembly
KW  - chloroplast ribosome
KW  - assembly factor
KW  - 30S subunit
KW  - RsgA
KW  - Arabidopsis thaliana
Y1  - 2018
U6  - https://doi.org/10.1111/tpj.14040
SN  - 0960-7412
SN  - 1365-313X
VL  - 96
IS  - 2
SP  - 404
EP  - 420
PB  - Wiley
CY  - Hoboken
ER  -