Searching for new cell wall protein genes in Arabidopsis

The objective of this study was to test an approach that combines bioinformatic and subcellular localization analysis to identify novel cell wall protein genes in Arabidopsis. Proteins with unknown function in the Arabidopsis genome were first identified and scanned for the presence of N-terminal signal peptides. The signal peptide-containing function-unknown proteins were further analyzed to eliminate the ones containing other sequences, such as endoplasmic reticulum and vacuole retention signals, that may prevent a protein from secretion into cell walls. The top ten genes passing the bioinformatic analysis were selected for protein subcellular localization using green fluorescence protein (GFP) as a reporter. A vector was constructed for high throughput gene-GFP fusion protein generation and overexpression in Arabidopsis for gene function analysis. Transformants of six genes showed reasonable expression of GFP fusion protein. However, none of the transformants showed GFP localization in cell walls. The low rate of new cell wall protein discovery suggests that the number of unidentified cell wall proteins in the Arabidopsis genome may be small.