DNA sequence encoding plant 2-acyltransferase

#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.

#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 considerable interest in altering lipid composition by the use of recombinant DNA technology (e.g. Knauf, TIBtech, February 1987, 40-47), but by no means all 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.

#The invention is illustrated by the following examples. The examples refer to the accompanying drawings, in which:

#FIG. 1: shows the cDNA sequence (SEQ ID NO: 3) derived in Example 2 and its derived protein sequence (SEQ ID NO: 4).

#FIG. 2: shows a comparison of the sequences of rape (SEQ ID NO: 6), maize (SEQ ID NO: 5) and the Limnanthes ‘1’ (SEQ ID NO: 4) clone.

#Construction of library

#Limnanthes douglasii plants were greenhouse-grown and seeds collected at stages III and IV, as defined for Limnanthes alba by Laurent and Huang, Plant Physiol., 99: 1711-1715 (1992) (majority were stage IV). Total RNA was isolated by a standard hot SDS method and mRNA purified by oligo dT-cellulose chromatography using methods detailed in the manual accompanying Pharmacia mRNA purification kit. A cDNA library was made from 5 μg polyA+ RNA using a cDNA synthesis kit from Pharmacia. The cDNA was primed with oligo dT and cloned as EcoRI fragments into the phage vector lambda ZAPII. A plasmid-based cDNA library was made from an unamplified aliquot of the lambda library by plasmid rescue with the helper phage R408 using protocols described in Delauney and Verma, Plant Molecular Biology, Manual A14: 1-23 (1990). During construction, 1×106 colonies (=cDNA clones) were plated and scraped into LB medium. This was grown for 3 hr and a plasmid preparation carried out to get a cDNA library representative of 1×106 cDNA clones from developing mid to late stage Limnanthes embryos.

#Isolation of Limnanthes ‘1’ clone homologous to maize clone