Screening for Gene Function Using the FOX (Full-Length cDNA OvereXpressor Gene) Hunting System

Mutant resources are indispensable for the characterization of the functions of genes. There are two types of mutants, loss-of-function and gain-of-function mutants. Recently, we have developed a novel system in plants that uses a gain-of-function approach and is named as the FOX (
f
ull-length c
DNAo
vere
x
pressor gene) hunting system. In this system,
Arabidopsis
full-length
cDNA
s (fl-cDNAs) are randomly over-expressed under the control of the
cauliflower mosaic virus
(
CaMV
)
35S
promoter in
Arabidopsis
plants. These transgenic plants, or
Arabidopsis
FOX lines, possess ectopically expressed fl-cDNAs in their genome. Chemical genomics is a newly emerging field that connects chemical biology with genomes. Since each FOX line expresses an excess amount of the protein from the transgene it can be resistant or hypersensitive to bioactive chemicals when the protein is the target for the chemical. In this protocol, we describe the procedure for identification of the fl-cDNAs responsible for the target of the chemical or for the signal transduction pathway involving the chemical.