Stomatal stem cell regulation by a novel protein in Arabidopsis

Stomata act as small valves that help in the regulation of gas exchange in plants. These valves arise from epidermal stem cells that asymmetrically divide to become meristemoids, which are precursor cells that eventually give rise to guard cells. Our lab used microarray-based gene expression profiling to identify genes that might play a role in maintaining or controlling meristemoid behavior. One gene, At5g60880, encodes a small protein that plays a role in stomata patterning. The sequence of this protein provides little information about its putative function. In order to gain insight into the function of this protein, we obtained mutant plants (SALK_86936) and characterized their phenotype. These plants exhibited abnormal asymmetric divisions resulting in clustered stomata. Since nothing is known about this protein, we determined the At5g60880 gene expression pattern by making transgenic plants carrying a fusion between the native At5g60880 promoter and green fluorescent protein (GFP). Confocal laser scanning microscopy was used to visualize the expression pattern of GFP in developing leaves. At5g60880 appears to be expressed in most epidermal cells. To better understand the possible activity of this protein, we also created transgenic plants used to deduce the protein subcellular localization. These plants constitutively express a translational fusion between the At5g60880 protein and GFP driven by the CaMV 35S promoter. Preliminary results reveal cortical and cytoplasmic localization of this fusion protein. Understanding the function of this novel protein will ultimately contribute to our knowledge of stomata patterning mechanisms, and more generally stern cell differentiation in plants