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. 2013 Sep 3;11(9):e1001649. doi: 10.1371/journal.pbio.1001649

Figure 8. A working model for control of FT expression by the dynamic cycles of histone acetylation and deacetylation at the end of LDs.

Figure 8

The coincidence of high CO mRNA expression with light exposure at the day's end leads to the CO protein accumulation towards dusk. CO directly binds to the FT proximal promoter, and CO activity at the FT locus may change the chromatin state and enables/gates AGL18 (and presumably AGL15) binding to the FT proximal promoter. AGL18 recruits AFR1/AFR2-HDAC to FT chromatin at dusk. In addition, the CO activity may also enable the recruitment of a HAT to FT chromatin. The opposing activities of HAT and AFR-HDAC on FT chromatin at the end of LDs conceivably modulate the acetylation dynamics of FT chromatin and set FT expression at an adequate level at dusk. At night, CO is rapidly degraded by proteasomes, which prevents the actions of HAT and AFR-HDAC on FT chromatin, resulting in a “silent” chromatin state. In early day, FT chromatin remains ‘silent’ due to lack of the CO protein. Day and night are indicated with white and gray shadings, respectively.