Mutations in the midway gene disrupt a Drosophila acyl coenzyme A: Diacylglycerol acyltransferase

Department of Cell Biology, Yale University, New Haven, Connecticut, United States
Genetics (Impact Factor: 5.96). 05/2002; 160(4):1511-8.
Source: PubMed


During Drosophila oogenesis, defective or unwanted egg chambers are eliminated during mid-oogenesis by programmed cell death. In addition, final cytoplasm transport from nurse cells to the oocyte depends upon apoptosis of the nurse cells. To study the regulation of germline apoptosis, we analyzed the midway mutant, in which egg chambers undergo premature nurse cell death and degeneration. The midway gene encodes a protein similar to mammalian acyl coenzyme A: diacylglycerol acyltransferase (DGAT), which converts diacylglycerol (DAG) into triacylglycerol (TAG). midway mutant egg chambers contain severely reduced levels of neutral lipids in the germline. Expression of midway in insect cells results in high levels of DGAT activity in vitro. These results show that midway encodes a functional DGAT and that changes in acylglycerol lipid metabolism disrupt normal egg chamber development in Drosophila.

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    • "Schizosaccharomyces pombe dgat2/pdat double mutant lost viability upon entry into the stationary phase, due to apoptosis, and DAG was demonstrated to mediate fatty acids-induced lipoapoptosis in yeast (Zhang et al., 2003). Drosophila DGAT1 mutant displayed severely reduced TAG in the germline and showed premature apoptosis and degeneration of nurse cells (Buszczak et al., 2002). These studies highlight the role of TAG biosynthesis in protecting yeast cells from fatty acid induced lipotoxicity. "
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    ABSTRACT: Diacylglycerol (DAG) acyltransferase catalyses the final and committed step of triacylglycerol biosynthesis. Eukaryotes commonly contain up to three distinct classes of DAG acyltransferases: acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), acyl-CoA:diacylglycerol acyltransferase 2 (DGAT2), and phospholipid:diacylglycerol acyltransferase (PDAT). The non-conventional oleaginous yeast, Yarrowia lipolytica, contains at least one homologue of each class and serves as a good model to understand the role of different DAG acyltransferases in the biosynthesis of oil, a critical cellular component that serves as a storage molecule as well as a buffer for free fatty acids. We used gene disruptions in Y. lipolytica and in vitro enzyme assays to confirm the identity of genes encoding all three DAG acyltransferases and demonstrate that together they account for almost all oil biosynthesis and that all three contribute significantly to its oil biosynthesis. In Y. lipolytica ATCC 20362 strain, the total lipid% dry cell weight (DCW) as a percentage of the wild-type strain in pdat, dgat1, dgat2, dgat1/dgat2 double mutant and dgat1/dgat2/pdat triple mutant was 70%, 57%, 36%, 18% and 13%, respectively.This is the first example of DGAT1 contributing significantly to oil biosynthesis in a microorganism. The triple mutant shows significant growth defect in both increased lag phase and slower growth rate, suggesting that oil biosynthesis contributes to normal growth in this strain.
    Preview · Article · Jan 2012 · Yeast
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    • "A mutant of DGAT (gene ID: W01A11.2) in Caenorhabditis elegans showed increased sensitivity to hypoxic injury (Mabon et al., 2009). Drosophila mutants in the midway gene (identified as a DGAT1) displayed severely reduced levels of neutral lipids in the germline and showed premature apoptosis and degeneration of nurse cells (Buszczak et al., 2002). Also, no mutant completely devoid of TAG has been found in oleaginous bacteria, such as Streptomyces coelicolor (Arabolaza et al., 2008), which may hint that deficiency of TAG synthesis genes may be lethal. "
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    ABSTRACT: Triacylglycerol (TAG) biosynthesis is a principal metabolic pathway in most organisms, and TAG is the major form of carbon storage in many plant seeds. Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is the only acyltransferase enzyme that has been confirmed to contribute to TAG biosynthesis in Arabidopsis thaliana seeds. However, dgat1 null mutants display only a 20 to 40% decrease in seed oil content. To determine whether other enzymes contribute to TAG synthesis, candidate genes were expressed in TAG-deficient yeast, candidate mutants were crossed with the dgat1-1 mutant, and target genes were suppressed by RNA interference (RNAi). An in vivo role for phospholipid:diacylglycerol acyltransferase 1 (PDAT1; At5g13640) in TAG synthesis was revealed in this study. After failing to obtain double homozygous plants from crossing dgat1-1 and pdat1-2, further investigation showed that the dgat1-1 pdat1-2 double mutation resulted in sterile pollen that lacked visible oil bodies. RNAi silencing of PDAT1 in a dgat1-1 background or DGAT1 in pdat1-1 background resulted in 70 to 80% decreases in oil content per seed and in disruptions of embryo development. These results establish in vivo involvement of PDAT1 in TAG biosynthesis, rule out major contributions by other candidate enzymes, and indicate that PDAT1 and DGAT1 have overlapping functions that are essential for normal pollen and seed development of Arabidopsis.
    Full-text · Article · Dec 2009 · The Plant Cell
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    • "Indeed, injection of ecdysone in virgin females was shown to lead to premature nurse cell death, suggesting that ecdysone may normally act to promote nurse cell death (Soller et al., 1999). Mutations in the midway gene, which encodes an acyl coenzyme A, diacyglyercol acyltransferase, result in premature actin bundle formation and egg chamber degeneration, indicating that lipid composition may influence the timing of nurse cell death (Buszczak et al., 2002). A recently described mutant, spinster, has egg chambers with normal nurse cell dumping but persisting nurse cell nuclei (Nakano et al., 2001), indicating that the processes of dumping and nurse cell nuclear breakdown can be separated. "
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    ABSTRACT: Programmed cell death is the most common fate of female germ cells in Drosophila and many animals. In Drosophila, oocytes form in individual egg chambers that are supported by germline nurse cells and surrounded by somatic follicle cells. As oogenesis proceeds, 15 nurse cells die for every oocyte that is produced. In addition to this developmentally regulated cell death, groups of germ cells or entire egg chambers may be induced to undergo apoptosis in response to starvation or other insults. Recent findings suggest that these different types of cell death involve distinct genetic pathways. This review focuses on progress towards elucidating the molecular mechanisms acting during programmed cell death in Drosophila oogenesis.
    Preview · Article · Nov 2004 · Developmental Biology
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