Chemistry: molecular biology and microbiology – Treatment of micro-organisms or enzymes with electrical or... – Modification of viruses
Patent
1995-08-04
1998-12-01
Patterson, Jr., Charles L.
Chemistry: molecular biology and microbiology
Treatment of micro-organisms or enzymes with electrical or...
Modification of viruses
435193, 4352523, 435410, 4353201, 536 232, C12N 910, C12N 1554
Patent
active
058437398
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to modified plants. In particular, the invention relates to plants modified such that at least part of the plant (for example seeds of the plant) is capable of yielding a commercially useful oil.
BACKGROUND OF THE INVENTION
Plants have long been a commercially valuable source of oil. Nutritional uses of plant-derived oils have hitherto been dominant, but attention is now turning additionally to plants as a source of industrially useful oils, for example as replacements for or improvements on mineral oils. Oil seeds, such as from rape, have a variety of lipids in them (Hildish & Williams, "Chemical Composition of Natural Lipids", Chapman Hall, London, 1964). There is now considerable interest in altering lipid composition by the use of recombinant DNA technology (Knauf, TIBtech, February 1987, 40-47), but by no means ail of the goals have been realised to date for a variety of reasons, in spite of the ever-increasing sophistication of the technology.
Success in tailoring the lipid content of plant-derived oils requires a firm understanding of the biochemistry and genes involved. Broadly, two approaches are available. First, plants may be modified to permit the synthesis of fatty acids which are new (for the plant); so, for example, laurate and/or stearate may be synthesised in rape. Secondly, the pattern and/or extent of incorporation of fatty acids into the glycerol backbone of the lipid may be altered. It is with this latter approach that the present invention is concerned, although the former approach may additionally be used.
Lipids are formed in plants by the addition of fatty acid moieties onto the glycerol backbone by a series of acyl transferase enzymes. There are three positions on the glycerol molecule at which fatty acid (acyl) moieties may be substituted, and the substitution reached at each position is catalysed by a position-specific enzyme: the enzymes are known as 1-, 2- and 3-acyltransferases, respectively.
One, but not the only, current aim of "lipid engineering" in plants is to provide oils including lipids with a high content of erucic (22:1) acid. Erucic acid-containing lipids are commercially desirable for a number of purposes, particularly as replacements to or supplements for mineral oils in certain circumstances, as alluded to above. In the case of oil seed rape (Brassica napus), one of the most significant oil producing crops in cultivation today, the specificity of the 2-acyltransferase enzyme positively discriminates against the incorporation of erucic acid at position 2. So, even in those cultivars of rape which are able to incorporate erucic acid at positions 1 and 3, where there is no (or at least reduced) discrimination against erucic acid, only a maximum 66% of the fatty acids incorporated into triacyl glycerols can be erucic acid. Such varieties of rape are known as HEAR (high erucic acid rape) varieties.
It would therefore be desirable to increase the erucic acid content of conventional oil seed rape, as well as HEAR varieties; the same can be said of oils of other vegetable oil crops such as maize, sunflower and soya, to name but a few examples. While in principle it may be thought possible to introduce into a desired plant DNA encoding a 2-acyltransferase of different fatty acid specificity, for example from a different plant, in practice there are a number of problems.
First, 2-acyltransferase and 3-acyltransferase are membrane bound, and therefore insoluble, enzymes. They have not been purified. This makes working with them difficult and rules out the use of many conventional DNA cloning procedures. This difficulty does not, paradoxically, lie in the way of cloning the gene (or at least cDNA) encoding the 1-acyltransferase enzyme, which is soluble: in fact, recombinant DNA work has already been undertaken on this enzyme for a completely different purpose, namely the enhancement of chilling resistance in tobacco plant leaves, by Murata et al (Nature 356 710-713 (1992)).
Secondly, very little is known about the 2- and 3-a
REFERENCES:
Bernerth, R. and M. Frentzen, "Utilization of Erucoyl-CoA by Acyltransferases from Developing Seeds of Brassica napus(L.) Involved in Triacylglycerol Biosynthesis," Plant Sci. 67:21-28 (1990).
Hares, W. and M. Frentzen, "Substrate specificities of the membrane-bound and partially purified microsomal acyl-CoA: 1-acylglycerol-3-phosphate acyltransferase from etiolated shoots of Pisum sativum(L.)," Planta 185:124-131 (1991).
Lohden, I. et al., "Acyl-CoA: 1-acylglycerol-3phosphate acyltransferase from developing seeds of Limnathes douglasii (B. Br.) and Brassica napus (L.)," in: Plant Lipid Biochemistry, Structure and Utilization: Proc. 9th Int. Symp. Plant Lipids, Quinn, P.J. and J.L. Harwood, eds., pp. 175-177 (1990).
International Search Report from Application PCT/GB93/02528 (1994).
Bernerth et al., Utilization of erucoly-CoA by acetyltransferases from developing seeds of Brassica napus (L.) involved in triaacylglycerol biosynthesis, Chemical Abstracts 113(3):20895a (1990).
Coleman J., Characterization of the Escherichia coli gene for 1-acyl-sn-glycerol-3-phosphate acyltransferase (plsC), Mol. Gen. Genet. 232:295-303 (Mar. 1992).
Hares et al., Substrate specificities of the membrane-bound and partially purified microsomal acyl-CoA:1-acylglycerol-=3-phosphate acyltransferase from etiolated shoots of Pisum savatium(L.), Chemical Abstracts 115:201740h (Nov. 1991).
Herrera-Estrella et al., Chimeric genes as dominant selectable markers in plant cells, EMBO J. 2(6):987-95 (1983).
Herrera-Estrella et al., Expression of chimaeric genes transferred into plant cells using a Ti-plasmid-derived vector, Nature 303:209-213 (1983).
Knauf V.C., The application of genetic engineering to oilseed crops, TibTech 5:40-47 (1987).
Loehden et al., Acyl-CoA:1-acylglycerol-3-phosphate acyltransferase from developing seeds of Limnanthes douglasii (R.Br.) and brassica napus (L.), Chemical Abstracts 116(9):79057u (Mar. 1992).
Oo & Huang, Lysophosphatidate Acyltransferase Activities in the Microsomes from Palm Endosperm, Maize Scutellum, and Rapeseed Cotyledon of Maturing seeds, Plant Physiol 91:1288-1295 (1989).
Peterek et al., Approaches of cloning the 1-acylglycerol-3-phosphate acyltransferase, 8th Workshop on plant lipid, 90th Conference of the Gesellschaft fur Biologische Chemie, Biol. Chem. 2Hoppe-Seyler 372(8):539 (Aug. 1991).
Peterek et al., Wege zur Klonierung der 1 Acetylgycerin-3-Phosphat-Acyltransferase, 47th Annual Meeting of the German Society for Fat Science, Fat Science Technology 93(11):417-418 (Nov. 1991).
Studier et al., Use of T7 RNA Polymerase to Direct Expression of Cloned Genes, Methods in Enzymology 185:60-89 (1990).
Wolter v. et al., Biochemical and Molecular Biological Approaches for Changing the Fatty Acid Composition of Rape Seed Oil, Abstract on p. 288, Fat Sci. Technol. 8:288-90 (Jun. 1991).
Brown Adrian Paul
Slabas Antoni Ryszard
Nickerson Biocem Limited
Patterson Jr. Charles L.
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