Reprogramming the translatome during daily light transitions as affected by cytosolic glyceraldehyde-3-phosphate dehydrogenase GAPC1/C2.

Dark-light and light-dark transitions during the day are switch points of leaf metabolism strongly affecting the regulatory state of the cells and this change was hypothesized to affect the translatome. Cytosolic glyceraldehyde-3-phosphate dehydrogenases GAPC1 and GAPC2 function in glycolysis, carbohydrate and energy metabolism. But GAPC1/C2 also realize moonlighting functions in gene expression and posttranscriptional regulation. This study addresses rapid reprogramming of the translatome at end of night and end of day in wild type (WT) Arabidopsis thaliana and a gapc1/c2 knockdown line, namely within 10 min after realizing the light switch. Metabolite profiling compared to WT established the reduced dynamics of gapc1/c2 to increase a set of metabolites at the start of day, particularly intermediates of citric acid cycle and linked pathways. Differences in metabolite changes were also detected at the end of day. Only small sets of transcripts changed in total RNA pool, however RNAseq revealed major alterations in polysome association at these transition points. The most pronounced difference between WT and gapc1/c2 was seen in the reorganization of the translatome at the start of night. These results are in line with the proposed hypothesis that GAPC1/C2 play a role in the control of the translatome during light/dark transitions.