Cell type specific gene expression map of Arabidopsis thaliana SAM.

Shoot apical meristem (SAM) of higher plant composed of a few distinct cell types. All the cells in a mature plant’s SAM derived from 30~35 stem cells reservoir which are located at the tip of the apex. Plants ability to give rise diverse cell types from a pool of pluripotent stem cells requires orchestrated gene network that controls the cell fate commitment during the meristem development. To understand, how gene regulatory networks control cell identities switches during cell differentiation requires resolution in recording their gene expression pattern at single cell resolution. An earlier expression map involving three-cell population of stem cell niche revealed complex expression pattern among the cell types1. We developed this approach further and report here a gene expression map using cell-sorting methods for fluorescent protein marked cells in Arabidopsis shoot. The map covered 10 cell populations. This gene expression map represents data from 10 different cell types from Arabidopsis SAM. It will be first step in defining the function of many unknown genes in model plant Arabidopsis. Based on the in situ hybridization we identified 7 new cell types specific gene expression patterns. The promoters of these genes were used to generate fluorescent reporters. After treating the SAM with protoplasting cocktail, we sorted the fluorescent protein tagged cells using fluorescent activated cell sorter (FACS). The purified cell population was used to isolate RNA. Two round of RNA amplification was performed before microarray hybridization.