The expression profile of LACS9 (strong expression in young rapidly expanding tissues) led us to characterize it as encoding the major chloroplast long-chain acyl-CoA synthetase (LACS). Central to this characterization were in vitro chloroplast import assays and localization studies with LACS9::GFP fusions. Another gene expressed in young rapidly expanding tissues is LACS2. GUS staining occurred exclusively in the epidermal cells suggesting that the LACS2 ligase may supply acyl-CoA for cutin or wax synthesis. The wax load and composition of lacs2-1 leaves and stems are normal but the cutin layer is reduced in thickness.
Information on protein subcellular localization and tissue-specific expression will allow us to distinguish specific functions for our genes, even when they belong to sub-families that act on the same set of substrates. We use other techniques, such as quantitative PCR and in situ RNA hybridization when these are appropriate.
We have experience using the Affymetrix 22K Gene Chip and can carry out our own transcript profiling experiments whenever results are not available from public databases or other researchers.