Abstract
A light-repressed transcript encodes the LrtA protein in cyanobacteria. We show that half-life of lrtA transcript from Synechocystis sp. PCC 6803 is higher in dark-treated cells as compared to light-grown cells, suggesting post-transcriptional control of lrtA expression. The lrtA 5´ untranslated leader region is involved in that darkness-dependent regulation. We also found that Synechocystis sp. PCC 6803 LrtA is a ribosome-associated protein present in both 30S and 70S ribosomal particles. In order to investigate the function of this protein we have constructed a deletion mutant of the lrtA gene. Cells lacking LrtA (∆lrtA) had significantly lower amount of 70S particles and a greater amount of 30S and 50S particles, suggesting a role of LrtA in stabilizing 70S particles. Synechocystis strains with different amounts of LrtA protein: wild-type, ∆lrtA, and LrtAS (overexpressing lrtA) showed no differences in their growth rate under standard laboratory conditions. However, a clear LrtA dose-dependent effect was observed in the presence of the antibiotic tylosin, being the LrtAS strains the most sensitive. Similar results were obtained under hyperosmotic stress caused by sorbitol. Conversely, after prolonged periods of starvation, ∆lrtA strains were delayed in their growth with respect to the wild-type and the LrtAS strains. A positive role of LrtA protein in post-stress survival is proposed.
Highlights
Photosynthetic organisms need to harmonize various processes to diurnal changes in light intensity and nutrient availability
The lrtA gene was originally identified in Synechococcus sp
The results presented here demonstrate that the Synechocystis LrtA protein is associated to ribosomal particles, indicating that in cyanobacteria, as in other bacterial groups, this protein family has a function in translation
Summary
Photosynthetic organisms need to harmonize various processes to diurnal changes in light intensity and nutrient availability. Numerous genome expression analyses have been carried out in these organisms, especially in the model Synechocystis sp. Most of these studies are related to the transcriptional response to different environmental changes [1]. Far fewer studies address the translational regulation in cyanobacteria. There is ever-increasing evidence that numerous protein factors interact with the ribosome to regulate protein synthesis and modulate the expression profile of the cell in response to different environmental stresses [2]. In this context, this study aims to advance in the knowledge of LrtA protein as a potential modulator of translation
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