Tissue-Specific GAL4 Expression Patterns as a Resource Enabling Targeted Gene Expression, Cell Type-Specific Transcript Profiling and Gene Function Characterization in the Arabidopsis Vascular System

Abstract

Cell type-specific fluorescent gene expression markers are a prerequisite for various strategies in functional genomics and developmental biology. To increase the resolution of vascular tissue analysis and to identify more genes expressed in the vasculature, we searched for expression in vascular tissues within a new collection of transactivated enhancer trap lines. Among 33 lines with vascular expression, we identified five lines with expression profiles marking procambial or procambium-associated cell states. In stem cross-sections we identified one line with phloem- and four with xylem-specific expression, as well as nine lines with expression in both phloem and xylem and two with cambial expression. For all lines, we also report the expression patterns in different organs and developmental stages. Special features of expression patterns include a line with auxin-dependent expression domains. We determined the flanking sequences of 21 enhancer trap insertions, 16 of which are found in, or in close proximity to, annotated genes and thus may reflect the expression patterns of natural promoters. Finally, we analyzed the loss-of-function phenotypes of 14 putatively affected genes. Remarkably, mutations in a gene encoding a putative F-box protein were associated with an auxin-hypersensitive hypocotyl elongation response. Our compendium provides a diverse selection of markers for different vascular cell states, which can be used for targeted gene expression, cell type-specific transcript profiling and gene function assignment in the plant vascular system.