Expression of a Bacterial Trehalose-6-phosphate Synthase otsA Increases Oil Accumulation in Plant Seeds and Vegetative Tissues.

Zhiyang Zhai,Regina Feil,John E Lunn,Jantana Keereetaweep,John Shanklin,Hui Liu

doi:10.3389/fpls.2021.656962

Abstract

We previously demonstrated that exogenous trehalose 6-phosphate (T6P) treatment stabilized WRINKLED1 (WRI1), a master transcriptional regulator of fatty acid (FA) synthesis and increased total FA content in Brassica napus (B. napus) embryo suspension cell culture. Here, we explore Arabidopsis lines heterologously expressing the Escherichia coli T6P synthase (otsA) or T6P phosphatase (otsB) to refine our understanding regarding the role of T6P in regulating fatty acid synthesis both in seeds and vegetative tissues. Arabidopsis 35S:otsA transgenic seeds showed an increase of 13% in fatty acid content compared to those of wild type (WT), while seeds of 35:otsB transgenic seeds showed a reduction of 12% in fatty acid content compared to WT. Expression of otsB significantly reduced the level of WRI1 and expression of its target genes in developing seeds. Like Arabidopsis seeds constitutively expressing otsA, transient expression of otsA in Nicotiana benthamiana leaves resulted in strongly elevated levels of T6P. This was accompanied by an increase of 29% in de novo fatty acid synthesis rate, a 2.3-fold increase in triacylglycerol (TAG) and a 20% increase in total fatty acid content relative to empty vector (EV) controls. Taken together, these data support the heterologous expression of otsA as an approach to increasing TAG accumulation in plant seeds and vegetative tissues.

Highlights

Lipids play key roles as structural components of cell membranes, energy-dense storage compounds, and cell signaling molecules
We showed that exogenous trehalose 6-phosphate (T6P) can be taken up by B. napus suspension cells and cause a significant increase in total Fatty acids (FA) content relative to sucrose- or sorbitol-treated (Zhai et al, 2018)
To test whether elevated levels of T6P resulting from the expression of otsA positively regulates FA accumulation in seeds, we obtained previously characterized transgenic Arabidopsis lines that constitutively express otsA with elevated T6P content, and otsB with reduced T6P content relative to wild type (WT) (Schluepmann et al, 2003; Wingler et al, 2012)

Summary

Introduction

Lipids play key roles as structural components of cell membranes, energy-dense storage compounds, and cell signaling molecules. Fatty acids (FA) are major components of triacylglycerols (TAG), which occur in all tissues but accumulate to very high levels within lipid droplets in plant seeds (Li-Beisson et al, 2013). In the presence of higher sugar levels, KIN10 phosphorylation of WRI1 is inhibited and WRI1 is stabilized, increasing the transcription of WRI1 target genes involved in FA synthesis (Zhai et al, 2017a). This regulatory mechanism, couples FA synthesis to the availability of cellular carbon and energy

Methods

Results

Conclusion