Abiotic stress in plants causes accumulation of reactive oxygen species (ROS) leading to the need for new protein synthesis to defend against ROS and to replace existing proteins that are damaged by oxidation. Functional plant ribosomes are critical for these activities, however we know little about the impact of oxidative stress on plant ribosome abundance, turnover, and function. Using Arabidopsis cell culture as a model system, we induced oxidative stress using 1 µm of H2 O2 or 5 µm menadione to more than halve cell growth rate and limit total protein content. We show that ribosome content on a total cell protein basis decreased in oxidatively stressed cells. However, overall protein synthesis rates on a ribosome abundance basis showed the resident ribosomes retained their function in oxidatively stressed cells. 15 N progressive labelling was used to calculate the rate of ribosome synthesis and degradation to track the fate of 62 r-proteins. The degradation rates and the synthesis rates of most r-proteins slowed following oxidative stress leading to an ageing population of ribosomes in stressed cells. However, there were exceptions to this trend; r-protein RPS14C doubled its degradation rate in both oxidative treatments. Overall, we show that ribosome abundance decreases and their age increases with oxidative stress in line with loss of cell growth rate and total cellular protein amount, but ribosome function of the ageing ribosomes appeared to be maintained concomittently with differences in the turnover rate and abundance of specific ribosomal proteins. Data are available via ProteomeXchange with identifier PXD012840.
Keywords: Arabidopsis thaliana; 14C-leucine assay; 15N-labelling; multiple reaction monitoring; oxidative stress; protein content measuring; ribosome purification; turnover study.
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