Characterisation of ZmKCS-1 and ZmKCS-2, two b-ketoacyl-CoA-synthases from maize, possibly involved in seedling wax biosynthesis --Frenzel, K, Janke, SA1, Brettschneider, R, da Costa e Silva, O2, Wienand, U
1Eppendorf-Netheler-Hinz GmbH
2BASF Plant Science LLC (Present address)
The epicuticular wax layer on plant leaves is a heterogeneous mixture of polymers synthesized in different biosynthetic pathways. Some components are derived from the fatty acid elongation pathway (Bianchi et al., Maydica 30:179-198, 1985). Fatty acids are elongated by a complex of four enzymes which successively add two carbon units to fatty acids. The ß-ketoacyl-CoA-synthase (ß-KCS) is a condensing enzyme that plays a key role in the fatty acid elongation complex (Millar et al., Plant J. 12:121-131, 1997).

Two different cDNAs ZmKCS-1 and ZmKCS-2 from maize, with high homology to the Cut 1 gene from A. thaliana (Millar et al., Plant Cell 11:825-838, 1999) and various other plant ß-KCSs, were isolated from a cDNA-library of germinating kernels and a cDNA-library of young seedlings. The two cDNAs show a high sequence similarity in the coding region but are differently expressed in the endosperm of germinating kernels, in young seedlings and in tassels. There is no expression in adult leaves and developing kernels.

Overexpression of ZmKCS-1 in yeast did not lead to a change in long chain fatty acid. This observation and the particularly high homology to the wax biosynthesis related ß-KCS Cut 1 from A. thaliana as well as the high expression of both genes during germination indicates an involvement of ZmKCS-1 and ZmKCS—2 in the biosynthesis of seedling wax precursors.

Antisense experiments in maize were carried out within a partial clone of ZmKCS-1. Young transgenic seedlings showed small changes in leaf wax composition. The precise gene function, however, remains unclear and has to be further examined.

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