Geonhee Hwang^1,†, Sara Kim^1,†, Jae-Yong Cho², Inyup Paik³, Jeong-Il Kim² & Eunkyoo Oh^1,*

¹ Department of Life Sciences, Korea University, Seoul, Korea
² Department of Biotechnology and Kumho Life Science Laboratory, Chonnam National University, Gwangju, Korea
³ Department of Molecular Biosciences, The Institute for Cellular and Molecular Biology, University of Texas, Austin, TX, USA

^† These authors contributed equally to this work

^*Corresponding author : Eunkyoo Oh

Growth plasticity is a key mechanism by which plants adapt to the ever-changing environmental conditions. Since growth is a highenergy-demanding and irreversible process, it is expected to be regulated by the integration of endogenous energy status as well as environmental conditions. Here, we show that trehalose-6-phosphate (T6P) functions as a sugar signaling molecule that coordinates thermoresponsive hypocotyl growth with endogenous sugar availability. We found that the loss of T6P SYNTHASE 1 (TPS1) in Arabidopsis thaliana impaired high-temperaturemediated hypocotyl growth. Consistently, the activity of PIF4, a transcription factor that positively regulates hypocotyl growth, was compromised in the tps1 mutant. We further show that, in the tps1 mutant, a sugar signaling kinase KIN10 directly phosphorylates and destabilizes PIF4. T6P inhibits KIN10 activity in a GRIKdependent manner, allowing PIF4 to promote hypocotyl growth at high temperatures. Together, our results demonstrate that T6P determines thermoresponsive growth through the KIN10-PIF4 signaling module. Such regulation of PIF4 by T6P integrates the temperature-signaling pathway with the endogenous sugar status, thus optimizing plant growth response to environmental stresses.

Keywords : Arabidopsis; PIF4; thermomorphogenesis; TPS1; trehalose-6-phosphate