6). Under HL+UV conditions, although KPT-8602 expression levels of both dnaA and ftsZ genes significantly increased at 15:00 compared to the 6:00 time point, the expression level was 3- to 5-fold lower than under HL at 15:00. The sepF gene expression pattern was characterized by a strong peak at the LDT in HL, but like for the other two genes, the diel variations of sepF expression levels were dramatically reduced in UV-irradiated cells. In both light conditions, the sepF expression

was maximum during the S phase (Fig. 6C). Figure 6 Gene expression patterns of L/D-synchronized Prochlorococcus marinus PCC9511 cultures under HL and UV growth conditions, as measured by qPCR. A,

dnaA. B, ftsZ. C, sepF. The percentage of cells TSA HDAC nmr in the S phase of the cell cycle under HL (solid line) and HL+UV (dashed line) are also shown for comparison. Error bars indicate mean deviation for two biological replicates. For each graph, transcript levels were normalized to the reference time point 6:00 in HL condition. Grey PXD101 and black bars indicate light and dark periods. Transcript levels of DNA repair genes are moderately affected by UV radiation Analyses of diel expression patterns of six genes representative of different DNA repair pathways were compared between HL and HL+UV conditions (Fig. 7). These patterns were very different among the six genes, suggesting a refined orchestration of the different pathways. A first set of DNA repair genes, including phrA (PMM0285), which codes for a DNA photolyase and uvrA (PMM1712), encoding the subunit A of the excinuclease

UvrABC, an enzyme of the nucleotide excision DNA repair (NER) pathway, was strongly expressed during the light period. Their expression levels followed more or less closely the diel cycle of irradiance (Fig. 7A). Interestingly, the relative expression levels of both genes were already high under HL and exposure to UV radiations did not provoke any further increase of these levels, even at midday. The only notable difference between the HL and HL+UV profiles was a slightly higher expression level at 9:00 am for both genes in the former condition (Fig. 7A). Tenofovir cell line Figure 7 Gene expression patterns of L/D-synchronized Prochlorococcus marinus PCC9511 cultures under HL and UV growth conditions, as measured by qPCR. A, phrA and uvrA. B, mutS and ruvC. C, recA and umuC. The percentage of cells in the S phase of the cell cycle under HL (solid line) and HL+UV (dashed line) are also shown for comparison. Error bars indicate mean deviation for two biological replicates. For each graph, transcript levels were normalized to the reference time point 6:00 in HL condition. Grey and black bars indicate light and dark periods.