Glandular trichomes of many plant species synthesize and secrete a variety of phytochemicals that play an important protective role against pathogens and pests. Acyl sugars, in particular, are powerful natural insecticides. We demonstrated the existence of the α-ketoacid elongation (αKAE) pathway, an alternative to the fatty acid synthase (FAS) pathway, for the extension of carbon chains of acyl groups in sugar esters (SE). The α-KAE pathway utilizes one carbon elongation per cycle in contrast to two carbons per cycle in FAS, and it was found to function in a variety of tobaccos and petunia. FAS-mediated elongation was confirmed to participate in the synthesis of SE acyl groups in Solanum pennellii and Datura metel, and also in the synthesis of odd-carbon-length acids of epicuticular waxes from in tobacco and Brassica oleraceae. We attempted to knock down (RNAi-mediated) the central for the α-KAE pathway condensing enzyme isopropyl malate synthase (IPMS) using two IPMS-related genes from S. pennellii. The RNAi constructs were introduced via Agrobacterium-mediated transformation of leaf discs of N. tabacum T.I. 1068, and the resulting plants displayed significant changes in 2-methylbutyric and 3-methylvaleric groups produced by glandular trichomes.
Kroumova, Antoaneta B. and Wagner, George J., "Pathways for Synthesis, and Possibilities for Genetic Modification of Sugar Ester Acyl Groups Produced by Trichomes of Solanaceous Species" (2009). Plant and Soil Sciences Faculty Publications. 65.