Question

FLC is the key repressor of flowering in the process of vernalization. Methylation of Lysine 9 of histone H3 (H3K9me) is a chromatin modification associated with heterochromatin. Methylation of Lysine 4 of histone H3 (H3K4me) is a chromatin modification associated with euchromatin. Which proteins do you expect to be active on the FLC gene at specific times of year?

H3K9 metyltransferase H3K4 metyltransferase RNA Polymerase II spring fall fall

H3K9 metyltransferase H3K4 metyltransferase RNA Polymerase II fall spring spring

H3K9 metyltransferase H3K4 metyltransferase RNA Polymerase II spring fall spring

H3K9 metyltransferase H3K4 metyltransferase RNA Polymerase II fall spring fall

Answer 1

The promotion of flowering in response to prolonged exposure to cold temperatures is an adaptation to prevent plants from flowering in the fall, prior to winter, and to enable them to flower in spring.

1) H3K4 metyltransferase active will be active on FLC gene in fall, preventing the transcription, hence RNA polymerase will be inactive too. So their will be no flowering

2) Their will be flowering as the FLC gene will be inactive in spring and H3K9 metyltransferase activity leads to gene activation and hence RNA polymerase will be active.

3) Their will be flowering as H3K9 metyltransferase will be inactive and FLC will be active during fall which unables the chromatin structure alteration but RNA polymerase will be active but will be unable to perform transcription due to unaltered chromatin structure.

4) Their will be flowering. H3K9 metyltransferase is associated with activation/transcription elongation. In spring, H3K9 metyltransferase will be active and hence RNA polymerase will be active too.