TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR4 Interacts with WRINKLED1 to Mediate Seed Oil Biosynthesis.

Que Kong,Liang Guo,Jenny J Mantyla,Ling Yuan,Sanjay K Singh,Christoph Benning,Sitakanta Pattanaik,Wei Ma

doi:10.1104/pp.20.00547

Abstract

Cross-family transcription factor (TF) interactions play critical roles in the regulation of plant developmental and metabolic pathways. WRINKLED1 (WRI1) is a key TF governing oil biosynthesis in plants. However, little is known about WRI1-interacting factors and their roles in oil biosynthesis. We screened a TF library using Arabidopsis (Arabidopsis thaliana) WRI1 (AtWRI1) as bait in yeast two-hybrid assays and identified three TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family TFs, namely TCP4, TCP10, and TCP24, as AtWRI1-interacting partners. The physical interaction between AtWRI1 and TCPs was further validated using bimolecular fluorescence complementation assays. TCPs play important roles in various plant developmental processes; however, their involvement in fatty acid biosynthesis was not previously known. Coexpression of TCP4, but not TCP10 or TCP24, with AtWRI1 reduced AtWRI1-mediated oil biosynthesis in Nicotiana benthamiana leaves. Transcriptomic analysis in transgenic Arabidopsis plants with enhanced TCP4 activity engineered by expressing rTCP4 (i.e. miR319-resistant TCP4) revealed that AtWRI1 target genes were significantly repressed. TCP4 expression is strongly correlated with AtWRI1 during embryo development. A tcp4 loss-of-function mutant, the jaw-D mutant with a strong reduction of TCP4 expression, and a tcp2 tcp4 tcp10 triple mutant accumulated more seed oil than wild-type Arabidopsis. In addition, TCP4 repressed the AtWRI1-mediated transactivation of the promoters of fatty acid biosynthetic genes. Collectively, our findings suggest that TCP4 represses fatty acid biosynthetic gene expression through interaction with AtWRI1, leading to a reduction of AtWRI1-mediated seed oil accumulation.

Highlights

Plant oils are important for both human diet and industry as renewable feed stocks
We demonstrated that a nuclear localization signal at the N-terminus (AtWRI133-41) enables AtWRI1 to localize to the nucleus, where it likely interacts with other factors in the regulation of target gene expression (Supplemental Figure S1)
Our results showed that TCP4, TCP10 and TCP24 interacted with AtWRI1 in yeast cells (Figure 1A; Supplemental Figure S2A)

Summary

Introduction

Plant oils are important for both human diet and industry as renewable feed stocks. Many plants synthesize triacylglycerol (TAG) in seeds as a crucial mechanism for storing and providing energy for seedling development (Chapman and Ohlrogge, 2012). Transcription factor (TF), WRINKLED1 (WRI1) is a key regulator of plant oil biosynthesis (Cernac and Benning, 2004; Masaki et al, 2005; Kong and Ma, 2018). Subsequent studies validated that the genes encoding proteins of late glycolysis and fatty acid biosynthesis are targets of AtWRI1 (Baud et al, 2007; Maeo et al., 2009). Transgenic plants overexpressing AtWRI1 or other WRI1 orthologs produce higher oil in seeds and leaves (Cernac and Benning, 2004; Shen et al, 2010; Yang et al, 2015). The 14-3-3 proteins interact with AtWRI1 in the mediation of AtWRI1 stability, transcriptional activity, and oil production (Ma et al, 2016). A subsequent study showed that trehalose 6-phosphate (T6P) stabilizes AtWRI1, resulting in increased fatty acid production through KIN10 activity suppression (Zhai et al, 2018)

Methods

Results

Conclusion