AUTHOR=Hwang Geonhee , Park Jeeyoon , Kim Soohwan , Park Jeonghyang , Seo Dain , Oh Eunkyoo 

TITLE=Overexpression of BBX18 Promotes Thermomorphogenesis Through the PRR5-PIF4 Pathway

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.782352

DOI=10.3389/fpls.2021.782352

ISSN=1664-462X

ABSTRACT=<p>Thermomorphogenesis is the morphological response of plants to an elevation in the ambient temperature, which is mediated by the bHLH transcription factor PIF4. The evening-expressed clock component, PRR5, directly represses the expression of <italic>PIF4</italic> mRNA. Additionally, PRR5 interacts with PIF4 protein and represses its transactivation activity, which in turn suppresses the thermoresponsive growth in the evening. Here, we found that the B-box zinc finger protein, BBX18, interacts with PRR5 through the B-Box2 domain. Deletion of the B-Box2 domain abolished the functions of BBX18, including the stimulation of <italic>PIF4</italic> mRNA expression and hypocotyl growth. Overexpression of <italic>BBX18</italic>, and not of <italic>B-Box2-deleted BBX18</italic>, restored the expression of thermoresponsive genes in the evening. We further show that BBX18 prevents PRR5 from inhibiting PIF4-mediated high temperature responses. Taken together, our results suggest that BBX18 regulates thermoresponsive growth through the PRR5-PIF4 pathway.</p>