Characterization of twoGL8paralogs reveals that the 3-ketoacyl reductase component of fatty acid elongase is essential for maize (Zea maysL.) development.

Prior analyses established that the maize (Zea maysL.)gl8agene encodes 3-ketoacyl reductase, a component of the fatty acid elongase required for the biosynthesis of very long chain fatty acids (VLCFAs). A paralogous gene,gl8b, has been identified that is 96% identical togl8a. Thegl8aandgl8bgenes map to syntenic chromosomal regions, have similar, but not identical, expression patterns, and encode proteins that are 97% identical. Both of these genes are required for the normal accumulation of cuticular waxes on seedling leaves. The chemical composition of the cuticular waxes fromgl8aandgl8bmutants indicates that these genes have at least overlapping, if not redundant, functions in cuticular wax biosynthesis. Althoughgl8aandgl8bdouble mutant kernels have endosperms that cannot be distinguished from wild-type siblings, these kernels are non-viable because their embryos fail to undergo normal development. Double mutant kernels accumulate substantially reduced levels of VLCFAs. VLCFAs are components of a variety of compounds, for example, cuticular waxes, suberin, and sphingolipids. Consistent with their essential nature in yeast, the accumulation of the ceramide moiety of sphingolipids is substantially reduced and their fatty acid composition altered ingl8a andgl8bdouble mutant kernels relative to wild-type kernels. Hence, we hypothesize that sphingolipids or other VLCFA-containing compounds are essential for normal embryo development. [ABSTRACT FROM AUTHOR]