Calgene Corporation

Ling Yuan

Jean C Kridl

Vic C Knauf

Deborah J Hawkins

Toni Alois Voelker

Katayoon Dehesh

Aubrey Jones

Methods of altering substrate specificity of plant acyl-ACP thioesterases, and engineered plant acyl-ACP thioesterases so produced are provided. The C-terminal two thirds portion of plant thioesterases is identified as desirable for such modifications. DNA sequences and constructs for expression of engineered thioesterases, as well as the novel thioesterases produced therefrom are also provided. Such DNA sequences may be used for expression of the engineered thioesterases in host cells, particularly seed cells of oilseed crop plants, for the modification of fatty acid composition. A C12 preferring plant acyl-ACP thioesterase described herein may be altered to obtain a plant thioesterase having approximately equal activity on C14 and C12 substrates. Further modification of the C12 enzyme yields a thioesterase having greater activity on C14 as compared to C12 substrates. Also provided in the instant invention are novel plant acyl-ACP thioesterase sequences from Cuphea palustris and mangosteen (Garcinia mangifera), which demonstrate desirable thioesterase activity profiles for plant genetic engineering applications.

Engineering plant thioesterases for altered substrate specificity

This invention relates to plant thioesterases, specifically plant acyl-ACP thioesterases having substantial activity on palmitoyl-ACP substrates. DNA constructs useful for the expression of a plant palmitoyl-ACP thioesterase in a plant seed cell are described. Such constructs will contain a DNA sequence encoding the plant palmitoyl-ACP thioesterase of interest under the control of regulatory elements capable of preferentially directing the expression of the plant palmitoyl-ACP thioesterase in seed tissue, as compared with other plant tissues, when such a construct is expressed in a transgenic plant. This invention also relates to methods of using a DNA sequence encoding a plant palmitoyl-ACP thioesterase for the modification of the proportion of free fatty acids produced in a plant seed cell. Plant palmitoyl-ACP thioesterase sequences exemplified herein include Cuphea, leek, mango and elm. Transgenic plants having increased levels of C16:0 fatty acids in their seeds as the result of expression of these palmitoyl-ACP thioesterase sequences are also provided.

Plant acyl-ACP thioesterase sequences

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Vacaville, CA, United States of America

Ling Yuan