AUTHOR=Son Ora , Zhang Chaoyue , Yang Xiaoyu , Duc Le Thi , Hur Yoon-Sun , Nam Kyoung Hee , Choi Soon-Young , Cheon Choong-Ill , Kim Sunghan TITLE=Identification of GA20ox2 as a target of ATHB2 and TCP13 during shade response JOURNAL=Frontiers in Plant Science VOLUME=14 YEAR=2023 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1158288 DOI=10.3389/fpls.2023.1158288 ISSN=1664-462X ABSTRACT=

The shade avoidance syndrome (SAS) is a collective adaptive response of plants under shade highlighted by characteristic phenotypes such as hypocotyl elongation, which is largely mediated by concerted actions of auxin and GA. We identified ATHB2, a homeodomain-leucine zipper (HD-Zip) domain transcription factor known to be rapidly induced under shade condition, as a positive regulator of GA biosynthesis necessary for the SAS by transactivating the expression of GA20ox2, a key gene in the GA biosynthesis pathway. Based on promoter deletion analysis, EMSA and ChIP assay, ATHB2 appears to regulate the GA20ox2 expression as a direct binding target. We also found that the GA20ox2 expression is under negative control by TCP13, the effect of which can be suppressed by presence of ATHB2. Considering a rapid induction kinetics of ATHB2, this relationship between ATHB2 and TCP13 may allow ATHB2 to play a shade-specific activator for GA20ox by derepressing a pre-existing activity of TCP13.