AUTHOR=Zhou Fei , Sun Tian-Hu , Zhao Lei , Pan Xi-Wu , Lu Shan 

TITLE=The bZIP transcription factor HY5 interacts with the promoter of the monoterpene synthase gene QH6 in modulating its rhythmic expression

JOURNAL=Frontiers in Plant Science

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.00304

DOI=10.3389/fpls.2015.00304

ISSN=1664-462X

ABSTRACT=<p>The <italic>Artemisia annua</italic> L. β-pinene synthase QH6 was previously determined to be circadian-regulated at the transcriptional level, showing a rhythmic fluctuation of steady-state transcript abundances. Here we isolated both the genomic sequence and upstream promoter region of <italic>QH6</italic>. Different regulatory elements, such as G-box (TGACACGTGGCA, −421 bp from the translation initiation site) which might have effects on rhythmic gene expression, were found. Using the yeast one-hybrid and electrophoretic mobility shift assay (EMSA), we confirmed that the bZIP transcription factor HY5 binds to this motif of <italic>QH6</italic>. Studies with promoter truncations before and after this motif suggested that this G-box was important for the diurnal fluctuation of the transgenic β-glucuronidase gene (<italic>GUS</italic>) transcript abundance in <italic>Arabidopsis thaliana</italic>. <italic>GUS</italic> gene driven by the promoter region immediately after G-box showed an arrhythmic expression in both light/dark (LD) and constant dark (DD) conditions, whereas the control with G-box retained its fluctuation in both LD and DD. We further transformed <italic>A. thaliana</italic> with the luciferase gene (<italic>LUC</italic>) driven by an 1400 bp fragment upstream <italic>QH6</italic> with its G-box intact or mutated, respectively. The luciferase activity assay showed that a peak in the early morning disappeared in the mutant. Gene expression analysis also demonstrated that the rhythmic expression of <italic>LUC</italic> was abolished in the <italic>hy5-1</italic> mutant.</p>