GAL4 GFP enhancer trap lines for analysis of stomatal guard cell development and gene expression

To facilitate the monitoring of guard cells during developmentand isolation, a population of 704 GAL4 GFP enhancer trap lineswas screened and four single insert lines with guard cell GFPexpression and one with developmentally-regulated guard cellGFP expression were identified. The location of the T-DNA inserts,the expression of the flanking genes, and the promoter activityof the genomic DNA upstream of the T-DNA were characterized.The results indicated that the GFP expression pattern in atleast one of the lines was due to elements in the intergenicDNA immediately upstream of the T-DNA, rather than due to theactivity of the promoters of genes flanking the insert, andprovide evidence for the involvement of Dof elements in regulatingguard cell gene expression. It is shown further that the GAL4GFP lines can be used to track the contribution of guard cellmaterial in vitro, and this method was used to assess the purityof guard cell samples obtained using two methods of guard cellisolation. Key words: Arabidopsis, development, enhancer trap, GFP, guard cells, stomata, T-DNA Received 21 July 2008; Revised 7 October 2008 Accepted 16 October 2008