Cell division and gene expression in plants

Fernan Federici, University of Cambridge, and Lionel Dupuy, Scottish Crop Research Institute

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Confocal micrograph showing the expression of different fluorescent proteins in the stem of a thale cress seedling (Arabidopsis thaliana). Arabidopsis was the first plant to have its entire genome sequenced and is an important model for studying plant biology. The middle of the image shows a region of high cell proliferation, which drives the growth and branching of the seedling.

What is cell division?

Cell division is the process by which all eukaryotic cells (cells that contain a nucleus) replicate, producing two identical daughter cells from one single parent cell. This process is known as mitosis. Cell division is a crucial event in growth and development as well as evolution. During cell division all the genetic material is duplicated before being split into two new nuclei; this process sometimes occurs with errors, causing genetic mutations. These mutations may lead to new coding sequences, which can alter genes and change the behaviours of the cell. Understanding more about the processing involved in cell division may provide a better understanding of how some cellular diseases occur.

Why are scientists looking at this?

Investigating cell growth and genetic activity in growing plant tissue can help scientists to understand the changes that occur in cells and tissues as they develop. This particular technique allows scientists to quantify changes in the genes that effect cell growth, which can be measured on a cell-by-cell basis in living plant tissue.

These plants have been genetically modified so that fluorescent proteins are associated with specific gene promoters (sequences of DNA that act as 'genetic switches' initiating the expression of a gene). So, when a promoter switches a gene on, a corresponding fluorescent protein is produced, allowing this gene expression to be visualised. The green fluorescence marks the gene under investigation, while the red highlights a gene with a known expression pattern and thus acts as a reference. Cells that are yellow indicate both genes are expressed. A third fluorescent protein is attached to the plasma membrane to outline each cell and clearly marks cell division. With computer software, scientists can track the relative changes in colour intensity to analyse how much of each gene is being expressed.