Glycerol-3-phosphate acyltransferase 4 is essential for the normal development of reproductive organs and the embryo in Brassica napus.

Xue Chen,Crystal L Snyder,Randall J Weselake,Guanqun Chen,Martin Truksa,Saleh Shah

doi:10.1093/jxb/eru199

Xue Chen, Crystal L Snyder + Show 4 more

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https://doi.org/10.1093/jxb/eru199

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Abstract

The enzyme sn-glycerol-3-phosphate acyltransferase 4 (GPAT4) is involved in the biosynthesis of plant lipid poly-esters. The present study further characterizes the enzymatic activities of three endoplasmic reticulum-bound GPAT4 isoforms of Brassica napus and examines their roles in the development of reproductive organs and the embryo. All three BnGPAT4 isoforms exhibited sn-2 acyltransferase and phosphatase activities with dicarboxylic acid-CoA as acyl donor. When non-substituted acyl-CoA was used as acyl donor, the rate of acylation was considerably lower and phosphatase activity was not manifested. RNA interference (RNAi)-mediated down-regulation of all GPAT4 homologues in B. napus under the control of the napin promoter caused abnormal development of several reproductive organs and reduced seed set. Microscopic examination and reciprocal crosses revealed that both pollen grains and developing embryo sacs of the B. napus gpat4 lines were affected. The gpat4 mature embryos showed decreased cutin content and altered monomer composition. The defective embryo development further affected the oil body morphology, oil content, and fatty acid composition in gpat4 seeds. These results suggest that GPAT4 has a critical role in the development of reproductive organs and the seed of B. napus.

Highlights

The sn-glycerol-3-phosphate acyltransferase (GPAT) family is involved in acyl-lipid biosynthesis and plays a pivotal role in plant development (Chen et al, 2011a)
A previous study of gpat4 RNA interference (RNAi) lines under the control of the CaMV35S promoter found that the only detectable phenotype was a cuticle defect on the epidermis (Chen et al, 2011b); two T1 lines exhibited abnormal inflorescence development and severely reduced seed yield, the same abnormality observed in the current napin promoter-directed gpat4 RNAi lines
It appeared that the napin promoter-directed RNAi construct was more effective in down-regulating the expression of glycerol-3-phosphate acyltransferase 4 (GPAT4) in the reproductive organs of B. napus

Summary

Introduction

The sn-glycerol-3-phosphate acyltransferase (GPAT) family is involved in acyl-lipid biosynthesis and plays a pivotal role in plant development (Chen et al, 2011a). GPAT catalyses the transfer of a fatty acid moiety from acyl-coenzyme A (acyl-CoA) or acyl-acyl carrier protein (acyl-ACP) to the sn-1 or 2 position of sn-glycerol 3-phosphate (G3P) forming lysophosphatidic acid (LPA). Certain GPATs possess phosphatase activity and result in the formation of monoacylglycerols (MAGs) (Yang et al, 2012). Its homologues have been cloned and characterized from several plant species including pea (Pisum sativum) and Arabidopsis (Weber et al, 1991; Nishida et al, 1993; Xu et al, 2006).

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