Microgenomics: gene expression analysis at the tissue-specific and single-cell levels.

Plant organs are composed of many different cell types and the analysis of 'bulk' material results in the average of all information in these cells. Therefore, this does not reflect any individuality of the tissues present in plants. This review briefly summarizes different sampling methods which provide tissue- and cell-specific samples, respectively. In addition, gene expression analysis tools that allow the analysis of transcripts in minute samples are discussed in detail. The combination of both approaches results in high resolution gene expression data, which increases understanding of plant physiology in such diverse areas as primary and secondary metabolism, plant defence or stress response.