A B-Box domain containing protein interacts with WRINKLED1 and modulates seed oil biosynthesis in Arabidopsis

A. R. Q. LIM¹, Q. KONG¹, A. NOOR, Y. Q. SONG, S. PATTANAIK, L. YUAN, and W. MA

School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore.

¹A.R.Q.L. and Q.K. contributed equally to this work.

Abstract

Combinatorial gene regulation modulated by cross-family transcriptional regulator interactions is a pivotal molecular mechanism in mediating plant metabolic and developmental processes. WRINKLED1 (WRI1) is an essential transcriptional regulator governing plant oil biosynthesis. Nevertheless, the information of the co-regulators of Arabidopsis WRI1 (AtWRI1) is still scarce. Here, we discovered B-Box domain containing protein (BBX) as a novel type of AtWRI1-interacting regulator. Physical interaction between AtWRI1 and BBX was validated by yeast-two-hybrid, in vitro pull-down, and bimolecular fluorescence complementation assays. Earlier studies showed that BBXs play important roles in diverse physiological processes in plant cells, such as plant growth, development, and responses to environmental stimuli. However, their participation in plant oil biosynthesis remains largely unclear. We found that BBX enhanced the transcriptional activity of AtWRI1 on plant oil biosynthetic genes. Further analysis revealed that transgenic Arabidopsis plants overexpressing BBX showed increased seed oil content, and BBX loss-of-function mutants exhibited decreased seed oil content. Taken together, our data suggest that the BBX transcriptional regulator mediates the expression of plant oil biosynthetic genes via interaction with AtWRI1, leading to improved oil generation. Our study characterizes a new AtWRI1-interacting BBX which allows for fine-tuning of seed oil biosynthesis.