Competitive hybridization: Theory and application in isolation and quantification of differentially regulated genes

Competitive hybridization is a simple yet powerful method that was develope d to screen cDNA libraries for differentially regulated genes. The method i s based on competition between unlabeled cDNA from the mRNA of one sample a nd labeled cDNA from another sample. By manipulating the amount of competin g unlabeled cDNA, background signals from the nonregulated genes can be inc reased or reduced, enabling the signals from differentially regulated genes to be contrasted and to be identified in a quantitative manner. To demonst rate the feasibility of the method, we screened a citrus cDNA library for e thylene-induced genes and identified three genes with different levels of e thylene induction. The mathematical basis of the method and its possible ap plication in gene chip technology are discussed. (C) 2000 Academic Press.