RICE ACYL-COA-BINDING PROTEIN6 Affects Acyl-CoA Homeostasis and Growth in Rice

Wei Meng,Mee-Len Chye,Lijian Xu,Xingshun Song,Yuhua Li,Rui Zhang,Sin Man Lam,Zhi-Yan Du,Fang Wang,Guanghou Shui

doi:10.1186/s12284-020-00435-y

Abstract

BackgroundsAcyl-coenzyme A (CoA) esters are important intermediates in lipid metabolism with regulatory properties. Acyl-CoA-binding proteins bind and transport acyl-CoAs to fulfill these functions. RICE ACYL-COA-BINDING PROTEIN6 (OsACBP6) is currently the only one peroxisome-localized plant ACBP that has been proposed to be involved in β-oxidation in transgenic Arabidopsis. The role of the peroxisomal ACBP (OsACBP6) in rice (Oryza sativa) was investigated.ResultsHere, we report on the function of OsACBP6 in rice. The osacbp6 mutant showed diminished growth with reduction in root meristem activity and leaf growth. Acyl-CoA profiling and lipidomic analysis revealed an increase in acyl-CoA content and a slight triacylglycerol accumulation caused by the loss of OsACBP6. Comparative transcriptomic analysis discerned the biological processes arising from the loss of OsACBP6. Reduced response to oxidative stress was represented by a decline in gene expression of a group of peroxidases and peroxidase activities. An elevation in hydrogen peroxide was observed in both roots and shoots/leaves of osacbp6. Taken together, loss of OsACBP6 not only resulted in a disruption of the acyl-CoA homeostasis but also peroxidase-dependent reactive oxygen species (ROS) homeostasis. In contrast, osacbp6-complemented transgenic rice displayed similar phenotype to the wild type rice, supporting a role for OsACBP6 in the maintenance of the acyl-CoA pool and ROS homeostasis. Furthermore, quantification of plant hormones supported the findings observed in the transcriptome and an increase in jasmonic acid level occurred in osacbp6.ConclusionsIn summary, OsACBP6 appears to be required for the efficient utilization of acyl-CoAs. Disruption of OsACBP6 compromises growth and led to provoked defense response, suggesting a correlation of enhanced acyl-CoAs content with defense responses.

Highlights

The primary role of acyl-coenzyme A (CoA) esters is to act as intermediates in lipid synthesis and breakdown (Neess et al 2015)
As OsACBP6 had been proposed to play a role in fatty acid β-oxidation through its acyl-CoA binding ability (Meng et al 2014), osacbp6 was examined for the typical phenotypes related to defects in β-oxidation
When osacbp6 and the wild type were tested in seed germination and seedling establishment in water, both germinated at about the same time but the development of the roots of osacbp6 seedlings was repressed with primary root reduction around 40% (Fig. 1d and e)

Summary

Introduction

The primary role of acyl-coenzyme A (CoA) esters is to act as intermediates in lipid synthesis and breakdown (Neess et al 2015). The cellular concentration of acylCoAs ranges from several μM to several hundred μM, the concentration of free unbound acyl-CoAs is unknown or could be extremely low (Neess et al 2015). AcylCoAs are bound to membrane lipids or proteins with high affinities, so that the concentration is strictly controlled to below the critical micelle concentration to avoid detergent effects that disrupt the membrane (Neess et al 2015). The small (10-kD) acyl-CoA-binding proteins (ACBPs) are known to bind acyl-CoA esters (Knudsen et al 2000). Considering that ACBPs bind acyl-CoAs with high affinities and broad ligand selectivity (C12-C26), ACBPs are believed to be the predominant acyl-CoA carriers/transporters (Knudsen et al 2000; Neess et al 2015; Lung and Chye 2016a, b; Guo et al 2017)

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